Added some obvious errors explanations

125 files changed, 435 insertions, 458 deletions

diff --git a/core/bind/core_bind.cpp b/core/bind/core_bind.cpp
index 5161f8bab2..30aaa0e646 100644
--- a/core/bind/core_bind.cpp
+++ b/core/bind/core_bind.cpp
@@ -145,13 +145,13 @@ _ResourceLoader::_ResourceLoader() {
 }
 
 Error _ResourceSaver::save(const String &p_path, const RES &p_resource, SaverFlags p_flags) {
-	ERR_FAIL_COND_V_MSG(p_resource.is_null(), ERR_INVALID_PARAMETER, "Can't save empty resource to path: " + String(p_path) + ".");
+	ERR_FAIL_COND_V_MSG(p_resource.is_null(), ERR_INVALID_PARAMETER, "Can't save empty resource to path '" + String(p_path) + "'.");
 	return ResourceSaver::save(p_path, p_resource, p_flags);
 }
 
 PoolVector<String> _ResourceSaver::get_recognized_extensions(const RES &p_resource) {
 
-	ERR_FAIL_COND_V(p_resource.is_null(), PoolVector<String>());
+	ERR_FAIL_COND_V_MSG(p_resource.is_null(), PoolVector<String>(), "It's not a reference to a valid Resource object.");
 	List<String> exts;
 	ResourceSaver::get_recognized_extensions(p_resource, &exts);
 	PoolVector<String> ret;
@@ -755,7 +755,7 @@ int64_t _OS::get_unix_time_from_datetime(Dictionary datetime) const {
 	ERR_FAIL_COND_V_MSG(month > 12 || month == 0, 0, "Invalid month value of: " + itos(month) + ".");
 
 	// Do this check after month is tested as valid
-	ERR_FAIL_COND_V_MSG(day > MONTH_DAYS_TABLE[LEAPYEAR(year)][month - 1] || day == 0, 0, "Invalid day value of: " + itos(day) + " which is larger than " + itos(MONTH_DAYS_TABLE[LEAPYEAR(year)][month - 1]) + " or 0.");
+	ERR_FAIL_COND_V_MSG(day > MONTH_DAYS_TABLE[LEAPYEAR(year)][month - 1] || day == 0, 0, "Invalid day value of '" + itos(day) + "' which is larger than '" + itos(MONTH_DAYS_TABLE[LEAPYEAR(year)][month - 1]) + "' or 0.");
 	// Calculate all the seconds from months past in this year
 	uint64_t SECONDS_FROM_MONTHS_PAST_THIS_YEAR = DAYS_PAST_THIS_YEAR_TABLE[LEAPYEAR(year)][month - 1] * SECONDS_PER_DAY;
 
@@ -1866,92 +1866,92 @@ bool _File::is_open() const {
 }
 String _File::get_path() const {
 
-	ERR_FAIL_COND_V(!f, "");
+	ERR_FAIL_COND_V_MSG(!f, "", "File must be opened before use.");
 	return f->get_path();
 }
 
 String _File::get_path_absolute() const {
 
-	ERR_FAIL_COND_V(!f, "");
+	ERR_FAIL_COND_V_MSG(!f, "", "File must be opened before use.");
 	return f->get_path_absolute();
 }
 
 void _File::seek(int64_t p_position) {
 
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
 	f->seek(p_position);
 }
 void _File::seek_end(int64_t p_position) {
 
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
 	f->seek_end(p_position);
 }
 int64_t _File::get_position() const {
 
-	ERR_FAIL_COND_V(!f, 0);
+	ERR_FAIL_COND_V_MSG(!f, 0, "File must be opened before use.");
 	return f->get_position();
 }
 
 int64_t _File::get_len() const {
 
-	ERR_FAIL_COND_V(!f, 0);
+	ERR_FAIL_COND_V_MSG(!f, 0, "File must be opened before use.");
 	return f->get_len();
 }
 
 bool _File::eof_reached() const {
 
-	ERR_FAIL_COND_V(!f, false);
+	ERR_FAIL_COND_V_MSG(!f, false, "File must be opened before use.");
 	return f->eof_reached();
 }
 
 uint8_t _File::get_8() const {
 
-	ERR_FAIL_COND_V(!f, 0);
+	ERR_FAIL_COND_V_MSG(!f, 0, "File must be opened before use.");
 	return f->get_8();
 }
 uint16_t _File::get_16() const {
 
-	ERR_FAIL_COND_V(!f, 0);
+	ERR_FAIL_COND_V_MSG(!f, 0, "File must be opened before use.");
 	return f->get_16();
 }
 uint32_t _File::get_32() const {
 
-	ERR_FAIL_COND_V(!f, 0);
+	ERR_FAIL_COND_V_MSG(!f, 0, "File must be opened before use.");
 	return f->get_32();
 }
 uint64_t _File::get_64() const {
 
-	ERR_FAIL_COND_V(!f, 0);
+	ERR_FAIL_COND_V_MSG(!f, 0, "File must be opened before use.");
 	return f->get_64();
 }
 
 float _File::get_float() const {
 
-	ERR_FAIL_COND_V(!f, 0);
+	ERR_FAIL_COND_V_MSG(!f, 0, "File must be opened before use.");
 	return f->get_float();
 }
 double _File::get_double() const {
 
-	ERR_FAIL_COND_V(!f, 0);
+	ERR_FAIL_COND_V_MSG(!f, 0, "File must be opened before use.");
 	return f->get_double();
 }
 real_t _File::get_real() const {
 
-	ERR_FAIL_COND_V(!f, 0);
+	ERR_FAIL_COND_V_MSG(!f, 0, "File must be opened before use.");
 	return f->get_real();
 }
 
 PoolVector<uint8_t> _File::get_buffer(int p_length) const {
 
 	PoolVector<uint8_t> data;
-	ERR_FAIL_COND_V(!f, data);
+	ERR_FAIL_COND_V_MSG(!f, data, "File must be opened before use.");
 
-	ERR_FAIL_COND_V(p_length < 0, data);
+	ERR_FAIL_COND_V_MSG(p_length < 0, data, "Length of buffer cannot be smaller than 0.");
 	if (p_length == 0)
 		return data;
 
 	Error err = data.resize(p_length);
-	ERR_FAIL_COND_V(err != OK, data);
+	ERR_FAIL_COND_V_MSG(err != OK, data, "Can't resize data to " + itos(p_length) + " elements.");
 
 	PoolVector<uint8_t>::Write w = data.write();
 	int len = f->get_buffer(&w[0], p_length);
@@ -1967,7 +1967,7 @@ PoolVector<uint8_t> _File::get_buffer(int p_length) const {
 
 String _File::get_as_text() const {
 
-	ERR_FAIL_COND_V(!f, String());
+	ERR_FAIL_COND_V_MSG(!f, String(), "File must be opened before use.");
 
 	String text;
 	size_t original_pos = f->get_position();
@@ -1997,12 +1997,12 @@ String _File::get_sha256(const String &p_path) const {
 
 String _File::get_line() const {
 
-	ERR_FAIL_COND_V(!f, String());
+	ERR_FAIL_COND_V_MSG(!f, String(), "File must be opened before use.");
 	return f->get_line();
 }
 
 Vector<String> _File::get_csv_line(const String &p_delim) const {
-	ERR_FAIL_COND_V(!f, Vector<String>());
+	ERR_FAIL_COND_V_MSG(!f, Vector<String>(), "File must be opened before use.");
 	return f->get_csv_line(p_delim);
 }
 
@@ -2031,83 +2031,83 @@ Error _File::get_error() const {
 
 void _File::store_8(uint8_t p_dest) {
 
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
 
 	f->store_8(p_dest);
 }
 void _File::store_16(uint16_t p_dest) {
 
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
 
 	f->store_16(p_dest);
 }
 void _File::store_32(uint32_t p_dest) {
 
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
 
 	f->store_32(p_dest);
 }
 void _File::store_64(uint64_t p_dest) {
 
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
 
 	f->store_64(p_dest);
 }
 
 void _File::store_float(float p_dest) {
 
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
 
 	f->store_float(p_dest);
 }
 void _File::store_double(double p_dest) {
 
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
 
 	f->store_double(p_dest);
 }
 void _File::store_real(real_t p_real) {
 
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
 
 	f->store_real(p_real);
 }
 
 void _File::store_string(const String &p_string) {
 
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
 
 	f->store_string(p_string);
 }
 
 void _File::store_pascal_string(const String &p_string) {
 
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
 
 	f->store_pascal_string(p_string);
 };
 
 String _File::get_pascal_string() {
 
-	ERR_FAIL_COND_V(!f, "");
+	ERR_FAIL_COND_V_MSG(!f, "", "File must be opened before use.");
 
 	return f->get_pascal_string();
 };
 
 void _File::store_line(const String &p_string) {
 
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
 	f->store_line(p_string);
 }
 
 void _File::store_csv_line(const Vector<String> &p_values, const String &p_delim) {
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
 	f->store_csv_line(p_values, p_delim);
 }
 
 void _File::store_buffer(const PoolVector<uint8_t> &p_buffer) {
 
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
 
 	int len = p_buffer.size();
 	if (len == 0)
@@ -2125,17 +2125,17 @@ bool _File::file_exists(const String &p_name) const {
 
 void _File::store_var(const Variant &p_var, bool p_full_objects) {
 
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
 	int len;
 	Error err = encode_variant(p_var, NULL, len, p_full_objects);
-	ERR_FAIL_COND(err != OK);
+	ERR_FAIL_COND_MSG(err != OK, "Error when trying to encode Variant.");
 
 	PoolVector<uint8_t> buff;
 	buff.resize(len);
 
 	PoolVector<uint8_t>::Write w = buff.write();
 	err = encode_variant(p_var, &w[0], len, p_full_objects);
-	ERR_FAIL_COND(err != OK);
+	ERR_FAIL_COND_MSG(err != OK, "Error when trying to encode Variant.");
 	w.release();
 
 	store_32(len);
@@ -2144,7 +2144,7 @@ void _File::store_var(const Variant &p_var, bool p_full_objects) {
 
 Variant _File::get_var(bool p_allow_objects) const {
 
-	ERR_FAIL_COND_V(!f, Variant());
+	ERR_FAIL_COND_V_MSG(!f, Variant(), "File must be opened before use.");
 	uint32_t len = get_32();
 	PoolVector<uint8_t> buff = get_buffer(len);
 	ERR_FAIL_COND_V((uint32_t)buff.size() != len, Variant());
@@ -2153,7 +2153,7 @@ Variant _File::get_var(bool p_allow_objects) const {
 
 	Variant v;
 	Error err = decode_variant(v, &r[0], len, NULL, p_allow_objects);
-	ERR_FAIL_COND_V(err != OK, Variant());
+	ERR_FAIL_COND_V_MSG(err != OK, Variant(), "Error when trying to encode Variant.");
 
 	return v;
 }
@@ -2258,7 +2258,7 @@ Error _Directory::open(const String &p_path) {
 
 Error _Directory::list_dir_begin(bool p_skip_navigational, bool p_skip_hidden) {
 
-	ERR_FAIL_COND_V(!d, ERR_UNCONFIGURED);
+	ERR_FAIL_COND_V_MSG(!d, ERR_UNCONFIGURED, "Directory must be opened before use.");
 
 	_list_skip_navigational = p_skip_navigational;
 	_list_skip_hidden = p_skip_hidden;
@@ -2268,7 +2268,7 @@ Error _Directory::list_dir_begin(bool p_skip_navigational, bool p_skip_hidden) {
 
 String _Directory::get_next() {
 
-	ERR_FAIL_COND_V(!d, "");
+	ERR_FAIL_COND_V_MSG(!d, "", "Directory must be opened before use.");
 
 	String next = d->get_next();
 	while (next != "" && ((_list_skip_navigational && (next == "." || next == "..")) || (_list_skip_hidden && d->current_is_hidden()))) {
@@ -2279,44 +2279,44 @@ String _Directory::get_next() {
 }
 bool _Directory::current_is_dir() const {
 
-	ERR_FAIL_COND_V(!d, false);
+	ERR_FAIL_COND_V_MSG(!d, false, "Directory must be opened before use.");
 	return d->current_is_dir();
 }
 
 void _Directory::list_dir_end() {
 
-	ERR_FAIL_COND(!d);
+	ERR_FAIL_COND_MSG(!d, "Directory must be opened before use.");
 	d->list_dir_end();
 }
 
 int _Directory::get_drive_count() {
 
-	ERR_FAIL_COND_V(!d, 0);
+	ERR_FAIL_COND_V_MSG(!d, 0, "Directory must be opened before use.");
 	return d->get_drive_count();
 }
 String _Directory::get_drive(int p_drive) {
 
-	ERR_FAIL_COND_V(!d, "");
+	ERR_FAIL_COND_V_MSG(!d, "", "Directory must be opened before use.");
 	return d->get_drive(p_drive);
 }
 int _Directory::get_current_drive() {
-	ERR_FAIL_COND_V(!d, 0);
+	ERR_FAIL_COND_V_MSG(!d, 0, "Directory must be opened before use.");
 	return d->get_current_drive();
 }
 
 Error _Directory::change_dir(String p_dir) {
 
-	ERR_FAIL_COND_V(!d, ERR_UNCONFIGURED);
+	ERR_FAIL_COND_V_MSG(!d, ERR_UNCONFIGURED, "Directory must be opened before use.");
 	return d->change_dir(p_dir);
 }
 String _Directory::get_current_dir() {
 
-	ERR_FAIL_COND_V(!d, "");
+	ERR_FAIL_COND_V_MSG(!d, "", "Directory must be opened before use.");
 	return d->get_current_dir();
 }
 Error _Directory::make_dir(String p_dir) {
 
-	ERR_FAIL_COND_V(!d, ERR_UNCONFIGURED);
+	ERR_FAIL_COND_V_MSG(!d, ERR_UNCONFIGURED, "Directory must be opened before use.");
 	if (!p_dir.is_rel_path()) {
 		DirAccess *d = DirAccess::create_for_path(p_dir);
 		Error err = d->make_dir(p_dir);
@@ -2327,7 +2327,7 @@ Error _Directory::make_dir(String p_dir) {
 }
 Error _Directory::make_dir_recursive(String p_dir) {
 
-	ERR_FAIL_COND_V(!d, ERR_UNCONFIGURED);
+	ERR_FAIL_COND_V_MSG(!d, ERR_UNCONFIGURED, "Directory must be opened before use.");
 	if (!p_dir.is_rel_path()) {
 		DirAccess *d = DirAccess::create_for_path(p_dir);
 		Error err = d->make_dir_recursive(p_dir);
@@ -2339,7 +2339,7 @@ Error _Directory::make_dir_recursive(String p_dir) {
 
 bool _Directory::file_exists(String p_file) {
 
-	ERR_FAIL_COND_V(!d, false);
+	ERR_FAIL_COND_V_MSG(!d, false, "Directory must be opened before use.");
 
 	if (!p_file.is_rel_path()) {
 		return FileAccess::exists(p_file);
@@ -2349,7 +2349,7 @@ bool _Directory::file_exists(String p_file) {
 }
 
 bool _Directory::dir_exists(String p_dir) {
-	ERR_FAIL_COND_V(!d, false);
+	ERR_FAIL_COND_V_MSG(!d, false, "Directory must be opened before use.");
 	if (!p_dir.is_rel_path()) {
 
 		DirAccess *d = DirAccess::create_for_path(p_dir);
@@ -2364,18 +2364,18 @@ bool _Directory::dir_exists(String p_dir) {
 
 int _Directory::get_space_left() {
 
-	ERR_FAIL_COND_V(!d, 0);
+	ERR_FAIL_COND_V_MSG(!d, 0, "Directory must be opened before use.");
 	return d->get_space_left() / 1024 * 1024; //return value in megabytes, given binding is int
 }
 
 Error _Directory::copy(String p_from, String p_to) {
 
-	ERR_FAIL_COND_V(!d, ERR_UNCONFIGURED);
+	ERR_FAIL_COND_V_MSG(!d, ERR_UNCONFIGURED, "Directory must be opened before use.");
 	return d->copy(p_from, p_to);
 }
 Error _Directory::rename(String p_from, String p_to) {
 
-	ERR_FAIL_COND_V(!d, ERR_UNCONFIGURED);
+	ERR_FAIL_COND_V_MSG(!d, ERR_UNCONFIGURED, "Directory must be opened before use.");
 	if (!p_from.is_rel_path()) {
 		DirAccess *d = DirAccess::create_for_path(p_from);
 		Error err = d->rename(p_from, p_to);
@@ -2387,7 +2387,7 @@ Error _Directory::rename(String p_from, String p_to) {
 }
 Error _Directory::remove(String p_name) {
 
-	ERR_FAIL_COND_V(!d, ERR_UNCONFIGURED);
+	ERR_FAIL_COND_V_MSG(!d, ERR_UNCONFIGURED, "Directory must be opened before use.");
 	if (!p_name.is_rel_path()) {
 		DirAccess *d = DirAccess::create_for_path(p_name);
 		Error err = d->remove(p_name);
@@ -2442,14 +2442,14 @@ String _Marshalls::variant_to_base64(const Variant &p_var, bool p_full_objects)
 
 	int len;
 	Error err = encode_variant(p_var, NULL, len, p_full_objects);
-	ERR_FAIL_COND_V(err != OK, "");
+	ERR_FAIL_COND_V_MSG(err != OK, "", "Error when trying to encode Variant.");
 
 	PoolVector<uint8_t> buff;
 	buff.resize(len);
 	PoolVector<uint8_t>::Write w = buff.write();
 
 	err = encode_variant(p_var, &w[0], len, p_full_objects);
-	ERR_FAIL_COND_V(err != OK, "");
+	ERR_FAIL_COND_V_MSG(err != OK, "", "Error when trying to encode Variant.");
 
 	String ret = CryptoCore::b64_encode_str(&w[0], len);
 	ERR_FAIL_COND_V(ret == "", ret);
@@ -2471,7 +2471,7 @@ Variant _Marshalls::base64_to_variant(const String &p_str, bool p_allow_objects)
 
 	Variant v;
 	Error err = decode_variant(v, &w[0], len, NULL, p_allow_objects);
-	ERR_FAIL_COND_V(err != OK, Variant());
+	ERR_FAIL_COND_V_MSG(err != OK, Variant(), "Error when trying to decode Variant.");
 
 	return v;
 };
@@ -2638,13 +2638,13 @@ void _Thread::_start_func(void *ud) {
 			}
 		}
 
-		ERR_FAIL_MSG("Could not call function '" + t->target_method.operator String() + "'' starting thread ID: " + t->get_id() + " Reason: " + reason + ".");
+		ERR_FAIL_MSG("Could not call function '" + t->target_method.operator String() + "' to start thread " + t->get_id() + ": " + reason + ".");
 	}
 }
 
 Error _Thread::start(Object *p_instance, const StringName &p_method, const Variant &p_userdata, Priority p_priority) {
 
-	ERR_FAIL_COND_V(active, ERR_ALREADY_IN_USE);
+	ERR_FAIL_COND_V_MSG(active, ERR_ALREADY_IN_USE, "Thread already started.");
 	ERR_FAIL_COND_V(!p_instance, ERR_INVALID_PARAMETER);
 	ERR_FAIL_COND_V(p_method == StringName(), ERR_INVALID_PARAMETER);
 	ERR_FAIL_INDEX_V(p_priority, PRIORITY_MAX, ERR_INVALID_PARAMETER);
@@ -2685,8 +2685,8 @@ bool _Thread::is_active() const {
 }
 Variant _Thread::wait_to_finish() {
 
-	ERR_FAIL_COND_V(!thread, Variant());
-	ERR_FAIL_COND_V(!active, Variant());
+	ERR_FAIL_COND_V_MSG(!thread, Variant(), "Thread must exist to wait for its completion.");
+	ERR_FAIL_COND_V_MSG(!active, Variant(), "Thread must be active to wait for its completion.");
 	Thread::wait_to_finish(thread);
 	Variant r = ret;
 	active = false;
diff --git a/core/class_db.cpp b/core/class_db.cpp
index 3ad59bc309..f52937bdca 100644
--- a/core/class_db.cpp
+++ b/core/class_db.cpp
@@ -340,7 +340,7 @@ StringName ClassDB::get_parent_class(const StringName &p_class) {
 	OBJTYPE_RLOCK;
 
 	ClassInfo *ti = classes.getptr(p_class);
-	ERR_FAIL_COND_V(!ti, StringName());
+	ERR_FAIL_COND_V_MSG(!ti, StringName(), "Cannot get class '" + String(p_class) + "'.");
 	return ti->inherits;
 }
 
@@ -350,7 +350,7 @@ ClassDB::APIType ClassDB::get_api_type(const StringName &p_class) {
 
 	ClassInfo *ti = classes.getptr(p_class);
 
-	ERR_FAIL_COND_V(!ti, API_NONE);
+	ERR_FAIL_COND_V_MSG(!ti, API_NONE, "Cannot get class '" + String(p_class) + "'.");
 	return ti->api;
 }
 
@@ -375,7 +375,7 @@ uint64_t ClassDB::get_api_hash(APIType p_api) {
 	for (List<StringName>::Element *E = names.front(); E; E = E->next()) {
 
 		ClassInfo *t = classes.getptr(E->get());
-		ERR_FAIL_COND_V(!t, 0);
+		ERR_FAIL_COND_V_MSG(!t, 0, "Cannot get class '" + String(E->get()) + "'.");
 		if (t->api != p_api || !t->exposed)
 			continue;
 		hash = hash_djb2_one_64(t->name.hash(), hash);
@@ -528,8 +528,8 @@ Object *ClassDB::instance(const StringName &p_class) {
 				ti = classes.getptr(compat_classes[p_class]);
 			}
 		}
-		ERR_FAIL_COND_V(!ti, NULL);
-		ERR_FAIL_COND_V(ti->disabled, NULL);
+		ERR_FAIL_COND_V_MSG(!ti, NULL, "Cannot get class '" + String(p_class) + "'.");
+		ERR_FAIL_COND_V_MSG(ti->disabled, NULL, "Class '" + String(p_class) + "' is disabled.");
 		ERR_FAIL_COND_V(!ti->creation_func, NULL);
 	}
 #ifdef TOOLS_ENABLED
@@ -545,7 +545,7 @@ bool ClassDB::can_instance(const StringName &p_class) {
 	OBJTYPE_RLOCK;
 
 	ClassInfo *ti = classes.getptr(p_class);
-	ERR_FAIL_COND_V(!ti, false);
+	ERR_FAIL_COND_V_MSG(!ti, false, "Cannot get class '" + String(p_class) + "'.");
 #ifdef TOOLS_ENABLED
 	if (ti->api == API_EDITOR && !Engine::get_singleton()->is_editor_hint()) {
 		return false;
@@ -560,7 +560,7 @@ void ClassDB::_add_class2(const StringName &p_class, const StringName &p_inherit
 
 	const StringName &name = p_class;
 
-	ERR_FAIL_COND(classes.has(name));
+	ERR_FAIL_COND_MSG(classes.has(name), "Class '" + String(p_class) + "' already exists.");
 
 	classes[name] = ClassInfo();
 	ClassInfo &ti = classes[name];
@@ -836,7 +836,7 @@ void ClassDB::add_signal(StringName p_class, const MethodInfo &p_signal) {
 #ifdef DEBUG_METHODS_ENABLED
 	ClassInfo *check = type;
 	while (check) {
-		ERR_FAIL_COND_MSG(check->signal_map.has(sname), "Type " + String(p_class) + " already has signal: " + String(sname) + ".");
+		ERR_FAIL_COND_MSG(check->signal_map.has(sname), "Class '" + String(p_class) + "' already has signal '" + String(sname) + "'.");
 		check = check->inherits_ptr;
 	}
 #endif
@@ -922,10 +922,10 @@ void ClassDB::add_property(StringName p_class, const PropertyInfo &p_pinfo, cons
 		mb_set = get_method(p_class, p_setter);
 #ifdef DEBUG_METHODS_ENABLED
 
-		ERR_FAIL_COND_MSG(!mb_set, "Invalid setter: " + p_class + "::" + p_setter + " for property: " + p_pinfo.name + ".");
+		ERR_FAIL_COND_MSG(!mb_set, "Invalid setter '" + p_class + "::" + p_setter + "' for property '" + p_pinfo.name + "'.");
 
 		int exp_args = 1 + (p_index >= 0 ? 1 : 0);
-		ERR_FAIL_COND_MSG(mb_set->get_argument_count() != exp_args, "Invalid function for setter: " + p_class + "::" + p_setter + " for property: " + p_pinfo.name + ".");
+		ERR_FAIL_COND_MSG(mb_set->get_argument_count() != exp_args, "Invalid function for setter '" + p_class + "::" + p_setter + " for property '" + p_pinfo.name + "'.");
 #endif
 	}
 
@@ -935,15 +935,15 @@ void ClassDB::add_property(StringName p_class, const PropertyInfo &p_pinfo, cons
 		mb_get = get_method(p_class, p_getter);
 #ifdef DEBUG_METHODS_ENABLED
 
-		ERR_FAIL_COND_MSG(!mb_get, "Invalid getter: " + p_class + "::" + p_getter + " for property: " + p_pinfo.name + ".");
+		ERR_FAIL_COND_MSG(!mb_get, "Invalid getter '" + p_class + "::" + p_getter + "' for property '" + p_pinfo.name + "'.");
 
 		int exp_args = 0 + (p_index >= 0 ? 1 : 0);
-		ERR_FAIL_COND_MSG(mb_get->get_argument_count() != exp_args, "Invalid function for getter: " + p_class + "::" + p_getter + " for property: " + p_pinfo.name + ".");
+		ERR_FAIL_COND_MSG(mb_get->get_argument_count() != exp_args, "Invalid function for getter '" + p_class + "::" + p_getter + "' for property: '" + p_pinfo.name + "'.");
 #endif
 	}
 
 #ifdef DEBUG_METHODS_ENABLED
-	ERR_FAIL_COND_MSG(type->property_setget.has(p_pinfo.name), "Object " + p_class + " already has property: " + p_pinfo.name + ".");
+	ERR_FAIL_COND_MSG(type->property_setget.has(p_pinfo.name), "Object '" + p_class + "' already has property '" + p_pinfo.name + "'.");
 #endif
 
 	OBJTYPE_WLOCK
@@ -1228,20 +1228,20 @@ MethodBind *ClassDB::bind_methodfi(uint32_t p_flags, MethodBind *p_bind, const c
 	ClassInfo *type = classes.getptr(instance_type);
 	if (!type) {
 		memdelete(p_bind);
-		ERR_FAIL_V_MSG(NULL, "Couldn't bind method '" + mdname + "' for instance: " + instance_type + ".");
+		ERR_FAIL_V_MSG(NULL, "Couldn't bind method '" + mdname + "' for instance '" + instance_type + "'.");
 	}
 
 	if (type->method_map.has(mdname)) {
 		memdelete(p_bind);
 		// overloading not supported
-		ERR_FAIL_V_MSG(NULL, "Method already bound: " + instance_type + "::" + mdname + ".");
+		ERR_FAIL_V_MSG(NULL, "Method already bound '" + instance_type + "::" + mdname + "'.");
 	}
 
 #ifdef DEBUG_METHODS_ENABLED
 
 	if (method_name.args.size() > p_bind->get_argument_count()) {
 		memdelete(p_bind);
-		ERR_FAIL_V_MSG(NULL, "Method definition provides more arguments than the method actually has: " + instance_type + "::" + mdname + ".");
+		ERR_FAIL_V_MSG(NULL, "Method definition provides more arguments than the method actually has '" + instance_type + "::" + mdname + "'.");
 	}
 
 	p_bind->set_argument_names(method_name.args);
@@ -1265,7 +1265,7 @@ MethodBind *ClassDB::bind_methodfi(uint32_t p_flags, MethodBind *p_bind, const c
 }
 
 void ClassDB::add_virtual_method(const StringName &p_class, const MethodInfo &p_method, bool p_virtual) {
-	ERR_FAIL_COND(!classes.has(p_class));
+	ERR_FAIL_COND_MSG(!classes.has(p_class), "Request for nonexistent class '" + p_class + "'.");
 
 	OBJTYPE_WLOCK;
 
@@ -1280,7 +1280,7 @@ void ClassDB::add_virtual_method(const StringName &p_class, const MethodInfo &p_
 
 void ClassDB::get_virtual_methods(const StringName &p_class, List<MethodInfo> *p_methods, bool p_no_inheritance) {
 
-	ERR_FAIL_COND(!classes.has(p_class));
+	ERR_FAIL_COND_MSG(!classes.has(p_class), "Request for nonexistent class '" + p_class + "'.");
 
 #ifdef DEBUG_METHODS_ENABLED
 
@@ -1304,7 +1304,7 @@ void ClassDB::set_class_enabled(StringName p_class, bool p_enable) {
 
 	OBJTYPE_WLOCK;
 
-	ERR_FAIL_COND(!classes.has(p_class));
+	ERR_FAIL_COND_MSG(!classes.has(p_class), "Request for nonexistent class '" + p_class + "'.");
 	classes[p_class].disabled = !p_enable;
 }
 
@@ -1319,7 +1319,7 @@ bool ClassDB::is_class_enabled(StringName p_class) {
 		}
 	}
 
-	ERR_FAIL_COND_V(!ti, false);
+	ERR_FAIL_COND_V_MSG(!ti, false, "Cannot get class '" + String(p_class) + "'.");
 	return !ti->disabled;
 }
 
@@ -1328,7 +1328,7 @@ bool ClassDB::is_class_exposed(StringName p_class) {
 	OBJTYPE_RLOCK;
 
 	ClassInfo *ti = classes.getptr(p_class);
-	ERR_FAIL_COND_V(!ti, false);
+	ERR_FAIL_COND_V_MSG(!ti, false, "Cannot get class '" + String(p_class) + "'.");
 	return ti->exposed;
 }
 
diff --git a/core/crypto/crypto.cpp b/core/crypto/crypto.cpp
index 925a01b36a..83a25da901 100644
--- a/core/crypto/crypto.cpp
+++ b/core/crypto/crypto.cpp
@@ -149,7 +149,7 @@ Error ResourceFormatSaverCrypto::save(const String &p_path, const RES &p_resourc
 	} else {
 		ERR_FAIL_V(ERR_INVALID_PARAMETER);
 	}
-	ERR_FAIL_COND_V(err != OK, err);
+	ERR_FAIL_COND_V_MSG(err != OK, err, "Cannot save Crypto resource to file '" + p_path + "'.");
 	return OK;
 }
 
diff --git a/core/engine.cpp b/core/engine.cpp
index 937439faaf..b9dc057257 100644
--- a/core/engine.cpp
+++ b/core/engine.cpp
@@ -38,7 +38,7 @@
 
 void Engine::set_iterations_per_second(int p_ips) {
 
-	ERR_FAIL_COND(p_ips <= 0);
+	ERR_FAIL_COND_MSG(p_ips <= 0, "Engine iterations per second must be greater than 0.");
 	ips = p_ips;
 }
 int Engine::get_iterations_per_second() const {
diff --git a/core/hash_map.h b/core/hash_map.h
index 81ddc376d0..38da1d59ab 100644
--- a/core/hash_map.h
+++ b/core/hash_map.h
@@ -112,7 +112,7 @@ private:
 
 	void erase_hash_table() {
 
-		ERR_FAIL_COND(elements);
+		ERR_FAIL_COND_MSG(elements, "Cannot erase hash table if there are still elements inside.");
 
 		memdelete_arr(hash_table);
 		hash_table = 0;
diff --git a/core/image.cpp b/core/image.cpp
index 900efb0eb0..e0b0a1f8be 100644
--- a/core/image.cpp
+++ b/core/image.cpp
@@ -885,10 +885,10 @@ void Image::resize(int p_width, int p_height, Interpolation p_interpolation) {
 
 	bool mipmap_aware = p_interpolation == INTERPOLATE_TRILINEAR /* || p_interpolation == INTERPOLATE_TRICUBIC */;
 
-	ERR_FAIL_COND(p_width <= 0);
-	ERR_FAIL_COND(p_height <= 0);
-	ERR_FAIL_COND(p_width > MAX_WIDTH);
-	ERR_FAIL_COND(p_height > MAX_HEIGHT);
+	ERR_FAIL_COND_MSG(p_width <= 0, "Image width cannot be greater than 0.");
+	ERR_FAIL_COND_MSG(p_height <= 0, "Image height cannot be greater than 0.");
+	ERR_FAIL_COND_MSG(p_width > MAX_WIDTH, "Image width cannot be greater than " + itos(MAX_WIDTH) + ".");
+	ERR_FAIL_COND_MSG(p_height > MAX_HEIGHT, "Image height cannot be greater than " + itos(MAX_HEIGHT) + ".");
 
 	if (p_width == width && p_height == height)
 		return;
@@ -1096,12 +1096,12 @@ void Image::crop_from_point(int p_x, int p_y, int p_width, int p_height) {
 
 	ERR_FAIL_COND_MSG(!_can_modify(format), "Cannot crop in compressed or custom image formats.");
 
-	ERR_FAIL_COND(p_x < 0);
-	ERR_FAIL_COND(p_y < 0);
-	ERR_FAIL_COND(p_width <= 0);
-	ERR_FAIL_COND(p_height <= 0);
-	ERR_FAIL_COND(p_x + p_width > MAX_WIDTH);
-	ERR_FAIL_COND(p_y + p_height > MAX_HEIGHT);
+	ERR_FAIL_COND_MSG(p_x < 0, "Start x position cannot be smaller than 0.");
+	ERR_FAIL_COND_MSG(p_y < 0, "Start y position cannot be smaller than 0.");
+	ERR_FAIL_COND_MSG(p_width <= 0, "Width of image must be greater than 0.");
+	ERR_FAIL_COND_MSG(p_height <= 0, "Height of image must be greater than 0.");
+	ERR_FAIL_COND_MSG(p_x + p_width > MAX_WIDTH, "End x position cannot be greater than " + itos(MAX_WIDTH) + ".");
+	ERR_FAIL_COND_MSG(p_y + p_height > MAX_HEIGHT, "End y position cannot be greater than " + itos(MAX_HEIGHT) + ".");
 
 	/* to save memory, cropping should be done in-place, however, since this function
 	   will most likely either not be used much, or in critical areas, for now it won't, because
@@ -2055,7 +2055,7 @@ Ref<Image> Image::get_rect(const Rect2 &p_area) const {
 
 void Image::blit_rect(const Ref<Image> &p_src, const Rect2 &p_src_rect, const Point2 &p_dest) {
 
-	ERR_FAIL_COND(p_src.is_null());
+	ERR_FAIL_COND_MSG(p_src.is_null(), "It's not a reference to a valid Image object.");
 	int dsize = data.size();
 	int srcdsize = p_src->data.size();
 	ERR_FAIL_COND(dsize == 0);
@@ -2105,16 +2105,16 @@ void Image::blit_rect(const Ref<Image> &p_src, const Rect2 &p_src_rect, const Po
 
 void Image::blit_rect_mask(const Ref<Image> &p_src, const Ref<Image> &p_mask, const Rect2 &p_src_rect, const Point2 &p_dest) {
 
-	ERR_FAIL_COND(p_src.is_null());
-	ERR_FAIL_COND(p_mask.is_null());
+	ERR_FAIL_COND_MSG(p_src.is_null(), "It's not a reference to a valid Image object.");
+	ERR_FAIL_COND_MSG(p_mask.is_null(), "It's not a reference to a valid Image object.");
 	int dsize = data.size();
 	int srcdsize = p_src->data.size();
 	int maskdsize = p_mask->data.size();
 	ERR_FAIL_COND(dsize == 0);
 	ERR_FAIL_COND(srcdsize == 0);
 	ERR_FAIL_COND(maskdsize == 0);
-	ERR_FAIL_COND(p_src->width != p_mask->width);
-	ERR_FAIL_COND(p_src->height != p_mask->height);
+	ERR_FAIL_COND_MSG(p_src->width != p_mask->width, "Source image width is different from mask width.");
+	ERR_FAIL_COND_MSG(p_src->height != p_mask->height, "Source image height is different from mask height.");
 	ERR_FAIL_COND(format != p_src->format);
 
 	Rect2i clipped_src_rect = Rect2i(0, 0, p_src->width, p_src->height).clip(p_src_rect);
@@ -2168,7 +2168,7 @@ void Image::blit_rect_mask(const Ref<Image> &p_src, const Ref<Image> &p_mask, co
 
 void Image::blend_rect(const Ref<Image> &p_src, const Rect2 &p_src_rect, const Point2 &p_dest) {
 
-	ERR_FAIL_COND(p_src.is_null());
+	ERR_FAIL_COND_MSG(p_src.is_null(), "It's not a reference to a valid Image object.");
 	int dsize = data.size();
 	int srcdsize = p_src->data.size();
 	ERR_FAIL_COND(dsize == 0);
@@ -2218,16 +2218,16 @@ void Image::blend_rect(const Ref<Image> &p_src, const Rect2 &p_src_rect, const P
 
 void Image::blend_rect_mask(const Ref<Image> &p_src, const Ref<Image> &p_mask, const Rect2 &p_src_rect, const Point2 &p_dest) {
 
-	ERR_FAIL_COND(p_src.is_null());
-	ERR_FAIL_COND(p_mask.is_null());
+	ERR_FAIL_COND_MSG(p_src.is_null(), "It's not a reference to a valid Image object.");
+	ERR_FAIL_COND_MSG(p_mask.is_null(), "It's not a reference to a valid Image object.");
 	int dsize = data.size();
 	int srcdsize = p_src->data.size();
 	int maskdsize = p_mask->data.size();
 	ERR_FAIL_COND(dsize == 0);
 	ERR_FAIL_COND(srcdsize == 0);
 	ERR_FAIL_COND(maskdsize == 0);
-	ERR_FAIL_COND(p_src->width != p_mask->width);
-	ERR_FAIL_COND(p_src->height != p_mask->height);
+	ERR_FAIL_COND_MSG(p_src->width != p_mask->width, "Source image width is different from mask width.");
+	ERR_FAIL_COND_MSG(p_src->height != p_mask->height, "Source image height is different from mask height.");
 	ERR_FAIL_COND(format != p_src->format);
 
 	Rect2i clipped_src_rect = Rect2i(0, 0, p_src->width, p_src->height).clip(p_src_rect);
diff --git a/core/image.h b/core/image.h
index f29a30cda0..94ee8a2c33 100644
--- a/core/image.h
+++ b/core/image.h
@@ -356,7 +356,7 @@ public:
 	void set_pixel(int p_x, int p_y, const Color &p_color);
 
 	void copy_internals_from(const Ref<Image> &p_image) {
-		ERR_FAIL_COND(p_image.is_null());
+		ERR_FAIL_COND_MSG(p_image.is_null(), "It's not a reference to a valid Image object.");
 		format = p_image->format;
 		width = p_image->width;
 		height = p_image->height;
diff --git a/core/input_map.cpp b/core/input_map.cpp
index 2a8ac435fe..05c75febf2 100644
--- a/core/input_map.cpp
+++ b/core/input_map.cpp
@@ -56,7 +56,7 @@ void InputMap::_bind_methods() {
 
 void InputMap::add_action(const StringName &p_action, float p_deadzone) {
 
-	ERR_FAIL_COND(input_map.has(p_action));
+	ERR_FAIL_COND_MSG(input_map.has(p_action), "InputMap already has action '" + String(p_action) + "'.");
 	input_map[p_action] = Action();
 	static int last_id = 1;
 	input_map[p_action].id = last_id;
@@ -66,7 +66,7 @@ void InputMap::add_action(const StringName &p_action, float p_deadzone) {
 
 void InputMap::erase_action(const StringName &p_action) {
 
-	ERR_FAIL_COND(!input_map.has(p_action));
+	ERR_FAIL_COND_MSG(!input_map.has(p_action), "Request for nonexistent InputMap action '" + String(p_action) + "'.");
 	input_map.erase(p_action);
 }
 
@@ -126,15 +126,15 @@ bool InputMap::has_action(const StringName &p_action) const {
 
 void InputMap::action_set_deadzone(const StringName &p_action, float p_deadzone) {
 
-	ERR_FAIL_COND(!input_map.has(p_action));
+	ERR_FAIL_COND_MSG(!input_map.has(p_action), "Request for nonexistent InputMap action '" + String(p_action) + "'.");
 
 	input_map[p_action].deadzone = p_deadzone;
 }
 
 void InputMap::action_add_event(const StringName &p_action, const Ref<InputEvent> &p_event) {
 
-	ERR_FAIL_COND(p_event.is_null());
-	ERR_FAIL_COND(!input_map.has(p_action));
+	ERR_FAIL_COND_MSG(p_event.is_null(), "It's not a reference to a valid InputEvent object.");
+	ERR_FAIL_COND_MSG(!input_map.has(p_action), "Request for nonexistent InputMap action '" + String(p_action) + "'.");
 	if (_find_event(input_map[p_action], p_event))
 		return; //already gots
 
@@ -143,13 +143,13 @@ void InputMap::action_add_event(const StringName &p_action, const Ref<InputEvent
 
 bool InputMap::action_has_event(const StringName &p_action, const Ref<InputEvent> &p_event) {
 
-	ERR_FAIL_COND_V(!input_map.has(p_action), false);
+	ERR_FAIL_COND_V_MSG(!input_map.has(p_action), false, "Request for nonexistent InputMap action '" + String(p_action) + "'.");
 	return (_find_event(input_map[p_action], p_event) != NULL);
 }
 
 void InputMap::action_erase_event(const StringName &p_action, const Ref<InputEvent> &p_event) {
 
-	ERR_FAIL_COND(!input_map.has(p_action));
+	ERR_FAIL_COND_MSG(!input_map.has(p_action), "Request for nonexistent InputMap action '" + String(p_action) + "'.");
 
 	List<Ref<InputEvent> >::Element *E = _find_event(input_map[p_action], p_event);
 	if (E)
@@ -158,7 +158,7 @@ void InputMap::action_erase_event(const StringName &p_action, const Ref<InputEve
 
 void InputMap::action_erase_events(const StringName &p_action) {
 
-	ERR_FAIL_COND(!input_map.has(p_action));
+	ERR_FAIL_COND_MSG(!input_map.has(p_action), "Request for nonexistent InputMap action '" + String(p_action) + "'.");
 
 	input_map[p_action].inputs.clear();
 }
@@ -192,7 +192,7 @@ bool InputMap::event_is_action(const Ref<InputEvent> &p_event, const StringName
 
 bool InputMap::event_get_action_status(const Ref<InputEvent> &p_event, const StringName &p_action, bool *p_pressed, float *p_strength) const {
 	Map<StringName, Action>::Element *E = input_map.find(p_action);
-	ERR_FAIL_COND_V_MSG(!E, false, "Request for nonexistent InputMap action: " + String(p_action) + ".");
+	ERR_FAIL_COND_V_MSG(!E, false, "Request for nonexistent InputMap action '" + String(p_action) + "'.");
 
 	Ref<InputEventAction> input_event_action = p_event;
 	if (input_event_action.is_valid()) {
@@ -333,6 +333,6 @@ void InputMap::load_default() {
 
 InputMap::InputMap() {
 
-	ERR_FAIL_COND(singleton);
+	ERR_FAIL_COND_MSG(singleton, "Singleton in InputMap already exist.");
 	singleton = this;
 }
diff --git a/core/io/config_file.cpp b/core/io/config_file.cpp
index 9063e028be..271e5c5a0b 100644
--- a/core/io/config_file.cpp
+++ b/core/io/config_file.cpp
@@ -111,7 +111,7 @@ void ConfigFile::get_sections(List<String> *r_sections) const {
 }
 void ConfigFile::get_section_keys(const String &p_section, List<String> *r_keys) const {
 
-	ERR_FAIL_COND(!values.has(p_section));
+	ERR_FAIL_COND_MSG(!values.has(p_section), "Cannont get keys from nonexistent section '" + p_section + "'.");
 
 	for (OrderedHashMap<String, Variant>::ConstElement E = values[p_section].front(); E; E = E.next()) {
 		r_keys->push_back(E.key());
diff --git a/core/io/file_access_compressed.cpp b/core/io/file_access_compressed.cpp
index 102cd9cf6c..a52c6f79c9 100644
--- a/core/io/file_access_compressed.cpp
+++ b/core/io/file_access_compressed.cpp
@@ -195,7 +195,7 @@ bool FileAccessCompressed::is_open() const {
 
 void FileAccessCompressed::seek(size_t p_position) {
 
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
 	if (writing) {
 
 		ERR_FAIL_COND(p_position > write_max);
@@ -227,7 +227,7 @@ void FileAccessCompressed::seek(size_t p_position) {
 
 void FileAccessCompressed::seek_end(int64_t p_position) {
 
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
 	if (writing) {
 
 		seek(write_max + p_position);
@@ -238,7 +238,7 @@ void FileAccessCompressed::seek_end(int64_t p_position) {
 }
 size_t FileAccessCompressed::get_position() const {
 
-	ERR_FAIL_COND_V(!f, 0);
+	ERR_FAIL_COND_V_MSG(!f, 0, "File must be opened before use.");
 	if (writing) {
 
 		return write_pos;
@@ -249,7 +249,7 @@ size_t FileAccessCompressed::get_position() const {
 }
 size_t FileAccessCompressed::get_len() const {
 
-	ERR_FAIL_COND_V(!f, 0);
+	ERR_FAIL_COND_V_MSG(!f, 0, "File must be opened before use.");
 	if (writing) {
 
 		return write_max;
@@ -260,7 +260,7 @@ size_t FileAccessCompressed::get_len() const {
 
 bool FileAccessCompressed::eof_reached() const {
 
-	ERR_FAIL_COND_V(!f, false);
+	ERR_FAIL_COND_V_MSG(!f, false, "File must be opened before use.");
 	if (writing) {
 		return false;
 	} else {
@@ -270,8 +270,8 @@ bool FileAccessCompressed::eof_reached() const {
 
 uint8_t FileAccessCompressed::get_8() const {
 
-	ERR_FAIL_COND_V(writing, 0);
-	ERR_FAIL_COND_V(!f, 0);
+	ERR_FAIL_COND_V_MSG(!f, 0, "File must be opened before use.");
+	ERR_FAIL_COND_V_MSG(writing, 0, "File has not been opened in read mode.");
 
 	if (at_end) {
 		read_eof = true;
@@ -301,8 +301,8 @@ uint8_t FileAccessCompressed::get_8() const {
 }
 int FileAccessCompressed::get_buffer(uint8_t *p_dst, int p_length) const {
 
-	ERR_FAIL_COND_V(writing, 0);
-	ERR_FAIL_COND_V(!f, 0);
+	ERR_FAIL_COND_V_MSG(!f, 0, "File must be opened before use.");
+	ERR_FAIL_COND_V_MSG(writing, 0, "File has not been opened in read mode.");
 
 	if (at_end) {
 		read_eof = true;
@@ -342,16 +342,16 @@ Error FileAccessCompressed::get_error() const {
 }
 
 void FileAccessCompressed::flush() {
-	ERR_FAIL_COND(!f);
-	ERR_FAIL_COND(!writing);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
+	ERR_FAIL_COND_MSG(!writing, "File has not been opened in read mode.");
 
 	// compressed files keep data in memory till close()
 }
 
 void FileAccessCompressed::store_8(uint8_t p_dest) {
 
-	ERR_FAIL_COND(!f);
-	ERR_FAIL_COND(!writing);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
+	ERR_FAIL_COND_MSG(!writing, "File has not been opened in read mode.");
 
 	WRITE_FIT(1);
 	write_ptr[write_pos++] = p_dest;
diff --git a/core/io/file_access_encrypted.cpp b/core/io/file_access_encrypted.cpp
index 77decc107d..e45a873978 100644
--- a/core/io/file_access_encrypted.cpp
+++ b/core/io/file_access_encrypted.cpp
@@ -41,7 +41,7 @@
 
 Error FileAccessEncrypted::open_and_parse(FileAccess *p_base, const Vector<uint8_t> &p_key, Mode p_mode) {
 
-	ERR_FAIL_COND_V(file != NULL, ERR_ALREADY_IN_USE);
+	ERR_FAIL_COND_V_MSG(file != NULL, ERR_ALREADY_IN_USE, "Can't open file while another file from path '" + file->get_path_absolute() + "' is open.");
 	ERR_FAIL_COND_V(p_key.size() != 32, ERR_INVALID_PARAMETER);
 
 	pos = 0;
@@ -205,7 +205,7 @@ bool FileAccessEncrypted::eof_reached() const {
 
 uint8_t FileAccessEncrypted::get_8() const {
 
-	ERR_FAIL_COND_V(writing, 0);
+	ERR_FAIL_COND_V_MSG(writing, 0, "File has not been opened in read mode.");
 	if (pos >= data.size()) {
 		eofed = true;
 		return 0;
@@ -217,7 +217,7 @@ uint8_t FileAccessEncrypted::get_8() const {
 }
 int FileAccessEncrypted::get_buffer(uint8_t *p_dst, int p_length) const {
 
-	ERR_FAIL_COND_V(writing, 0);
+	ERR_FAIL_COND_V_MSG(writing, 0, "File has not been opened in read mode.");
 
 	int to_copy = MIN(p_length, data.size() - pos);
 	for (int i = 0; i < to_copy; i++) {
@@ -239,7 +239,7 @@ Error FileAccessEncrypted::get_error() const {
 
 void FileAccessEncrypted::store_buffer(const uint8_t *p_src, int p_length) {
 
-	ERR_FAIL_COND(!writing);
+	ERR_FAIL_COND_MSG(!writing, "File has not been opened in read mode.");
 
 	if (pos < data.size()) {
 
@@ -259,14 +259,14 @@ void FileAccessEncrypted::store_buffer(const uint8_t *p_src, int p_length) {
 }
 
 void FileAccessEncrypted::flush() {
-	ERR_FAIL_COND(!writing);
+	ERR_FAIL_COND_MSG(!writing, "File has not been opened in read mode.");
 
 	// encrypted files keep data in memory till close()
 }
 
 void FileAccessEncrypted::store_8(uint8_t p_dest) {
 
-	ERR_FAIL_COND(!writing);
+	ERR_FAIL_COND_MSG(!writing, "File has not been opened in read mode.");
 
 	if (pos < data.size()) {
 		data.write[pos] = p_dest;
diff --git a/core/io/file_access_memory.cpp b/core/io/file_access_memory.cpp
index fbcf5b8021..c0acd36751 100644
--- a/core/io/file_access_memory.cpp
+++ b/core/io/file_access_memory.cpp
@@ -90,7 +90,7 @@ Error FileAccessMemory::_open(const String &p_path, int p_mode_flags) {
 	//name = DirAccess::normalize_path(name);
 
 	Map<String, Vector<uint8_t> >::Element *E = files->find(name);
-	ERR_FAIL_COND_V(!E, ERR_FILE_NOT_FOUND);
+	ERR_FAIL_COND_V_MSG(!E, ERR_FILE_NOT_FOUND, "Can't find file '" + p_path + "'.");
 
 	data = E->get().ptrw();
 	length = E->get().size();
diff --git a/core/io/file_access_network.cpp b/core/io/file_access_network.cpp
index d1c7f5c334..e653a924ba 100644
--- a/core/io/file_access_network.cpp
+++ b/core/io/file_access_network.cpp
@@ -195,7 +195,7 @@ Error FileAccessNetworkClient::connect(const String &p_host, int p_port, const S
 
 	DEBUG_PRINT("IP: " + String(ip) + " port " + itos(p_port));
 	Error err = client->connect_to_host(ip, p_port);
-	ERR_FAIL_COND_V(err, err);
+	ERR_FAIL_COND_V_MSG(err != OK, err, "Cannot connect to host with IP: " + String(ip) + " and port: " + itos(p_port));
 	while (client->get_status() == StreamPeerTCP::STATUS_CONNECTING) {
 		//DEBUG_PRINT("trying to connect....");
 		OS::get_singleton()->delay_usec(1000);
@@ -339,7 +339,7 @@ bool FileAccessNetwork::is_open() const {
 
 void FileAccessNetwork::seek(size_t p_position) {
 
-	ERR_FAIL_COND(!opened);
+	ERR_FAIL_COND_MSG(!opened, "File must be opened before use.");
 	eof_flag = p_position > total_size;
 
 	if (p_position >= total_size) {
@@ -355,18 +355,18 @@ void FileAccessNetwork::seek_end(int64_t p_position) {
 }
 size_t FileAccessNetwork::get_position() const {
 
-	ERR_FAIL_COND_V(!opened, 0);
+	ERR_FAIL_COND_V_MSG(!opened, 0, "File must be opened before use.");
 	return pos;
 }
 size_t FileAccessNetwork::get_len() const {
 
-	ERR_FAIL_COND_V(!opened, 0);
+	ERR_FAIL_COND_V_MSG(!opened, 0, "File must be opened before use.");
 	return total_size;
 }
 
 bool FileAccessNetwork::eof_reached() const {
 
-	ERR_FAIL_COND_V(!opened, false);
+	ERR_FAIL_COND_V_MSG(!opened, false, "File must be opened before use.");
 	return eof_flag;
 }
 
diff --git a/core/io/file_access_pack.cpp b/core/io/file_access_pack.cpp
index d49d36c2b9..a4821e0ce8 100644
--- a/core/io/file_access_pack.cpp
+++ b/core/io/file_access_pack.cpp
@@ -321,7 +321,7 @@ FileAccessPack::FileAccessPack(const String &p_path, const PackedData::PackedFil
 		pf(p_file),
 		f(FileAccess::open(pf.pack, FileAccess::READ)) {
 
-	ERR_FAIL_COND_MSG(!f, "Can't open pack-referenced file: " + String(pf.pack) + ".");
+	ERR_FAIL_COND_MSG(!f, "Can't open pack-referenced file '" + String(pf.pack) + "'.");
 
 	f->seek(pf.offset);
 	pos = 0;
diff --git a/core/io/file_access_zip.cpp b/core/io/file_access_zip.cpp
index be28c9a877..083f56d92c 100644
--- a/core/io/file_access_zip.cpp
+++ b/core/io/file_access_zip.cpp
@@ -117,7 +117,7 @@ static void godot_free(voidpf opaque, voidpf address) {
 
 void ZipArchive::close_handle(unzFile p_file) const {
 
-	ERR_FAIL_COND(!p_file);
+	ERR_FAIL_COND_MSG(!p_file, "Cannot close a file if none is open.");
 	FileAccess *f = (FileAccess *)unzGetOpaque(p_file);
 	unzCloseCurrentFile(p_file);
 	unzClose(p_file);
@@ -126,11 +126,11 @@ void ZipArchive::close_handle(unzFile p_file) const {
 
 unzFile ZipArchive::get_file_handle(String p_file) const {
 
-	ERR_FAIL_COND_V(!file_exists(p_file), NULL);
+	ERR_FAIL_COND_V_MSG(!file_exists(p_file), NULL, "File '" + p_file + " doesn't exist.");
 	File file = files[p_file];
 
 	FileAccess *f = FileAccess::open(packages[file.package].filename, FileAccess::READ);
-	ERR_FAIL_COND_V(!f, NULL);
+	ERR_FAIL_COND_V_MSG(!f, NULL, "Cannot open file '" + packages[file.package].filename + "'.");
 
 	zlib_filefunc_def io;
 	zeromem(&io, sizeof(io));
diff --git a/core/io/image_loader.cpp b/core/io/image_loader.cpp
index a759e615c7..095c2abb54 100644
--- a/core/io/image_loader.cpp
+++ b/core/io/image_loader.cpp
@@ -46,14 +46,14 @@ bool ImageFormatLoader::recognize(const String &p_extension) const {
 }
 
 Error ImageLoader::load_image(String p_file, Ref<Image> p_image, FileAccess *p_custom, bool p_force_linear, float p_scale) {
-	ERR_FAIL_COND_V(p_image.is_null(), ERR_INVALID_PARAMETER);
+	ERR_FAIL_COND_V_MSG(p_image.is_null(), ERR_INVALID_PARAMETER, "It's not a reference to a valid Image object.");
 
 	FileAccess *f = p_custom;
 	if (!f) {
 		Error err;
 		f = FileAccess::open(p_file, FileAccess::READ, &err);
 		if (!f) {
-			ERR_PRINTS("Error opening file: " + p_file);
+			ERR_PRINTS("Error opening file '" + p_file + "'.");
 			return err;
 		}
 	}
diff --git a/core/io/ip.cpp b/core/io/ip.cpp
index 3d87131b51..f1b6570799 100644
--- a/core/io/ip.cpp
+++ b/core/io/ip.cpp
@@ -305,7 +305,7 @@ IP *(*IP::_create)() = NULL;
 
 IP *IP::create() {
 
-	ERR_FAIL_COND_V(singleton, NULL);
+	ERR_FAIL_COND_V_MSG(singleton, NULL, "IP singleton already exist.");
 	ERR_FAIL_COND_V(!_create, NULL);
 	return _create();
 }
diff --git a/core/io/ip_address.cpp b/core/io/ip_address.cpp
index df4be9b9fd..0980027f42 100644
--- a/core/io/ip_address.cpp
+++ b/core/io/ip_address.cpp
@@ -181,7 +181,7 @@ bool IP_Address::is_ipv4() const {
 }
 
 const uint8_t *IP_Address::get_ipv4() const {
-	ERR_FAIL_COND_V(!is_ipv4(), &(field8[12])); // Not the correct IPv4 (it's an IPv6), but we don't want to return a null pointer risking an engine crash.
+	ERR_FAIL_COND_V_MSG(!is_ipv4(), &(field8[12]), "IPv4 requested, but current IP is IPv6."); // Not the correct IPv4 (it's an IPv6), but we don't want to return a null pointer risking an engine crash.
 	return &(field8[12]);
 }
 
diff --git a/core/io/marshalls.cpp b/core/io/marshalls.cpp
index b386feb14c..2ae542bca7 100644
--- a/core/io/marshalls.cpp
+++ b/core/io/marshalls.cpp
@@ -478,7 +478,7 @@ Error decode_variant(Variant &r_variant, const uint8_t *p_buffer, int p_len, int
 
 				int used;
 				Error err = decode_variant(key, buf, len, &used, p_allow_objects);
-				ERR_FAIL_COND_V(err, err);
+				ERR_FAIL_COND_V_MSG(err != OK, err, "Error when trying to decode Variant.");
 
 				buf += used;
 				len -= used;
@@ -487,7 +487,7 @@ Error decode_variant(Variant &r_variant, const uint8_t *p_buffer, int p_len, int
 				}
 
 				err = decode_variant(value, buf, len, &used, p_allow_objects);
-				ERR_FAIL_COND_V(err, err);
+				ERR_FAIL_COND_V_MSG(err != OK, err, "Error when trying to decode Variant.");
 
 				buf += used;
 				len -= used;
@@ -522,7 +522,7 @@ Error decode_variant(Variant &r_variant, const uint8_t *p_buffer, int p_len, int
 				int used = 0;
 				Variant v;
 				Error err = decode_variant(v, buf, len, &used, p_allow_objects);
-				ERR_FAIL_COND_V(err, err);
+				ERR_FAIL_COND_V_MSG(err != OK, err, "Error when trying to decode Variant.");
 				buf += used;
 				len -= used;
 				varr.push_back(v);
diff --git a/core/io/multiplayer_api.cpp b/core/io/multiplayer_api.cpp
index ed6905c9a6..0ba84d0c8f 100644
--- a/core/io/multiplayer_api.cpp
+++ b/core/io/multiplayer_api.cpp
@@ -917,8 +917,7 @@ int MultiplayerAPI::_get_bandwidth_usage(const Vector<BandwidthFrame> &p_buffer,
 		i = (i + p_buffer.size() - 1) % p_buffer.size();
 	}
 
-	ERR_EXPLAIN("Reached the end of the bandwidth profiler buffer, values might be inaccurate.");
-	ERR_FAIL_COND_V(i == p_pointer, total_bandwidth);
+	ERR_FAIL_COND_V_MSG(i == p_pointer, total_bandwidth, "Reached the end of the bandwidth profiler buffer, values might be inaccurate.");
 	return total_bandwidth;
 }
 
diff --git a/core/io/packet_peer.cpp b/core/io/packet_peer.cpp
index 1c792c43d1..821a04ebad 100644
--- a/core/io/packet_peer.cpp
+++ b/core/io/packet_peer.cpp
@@ -101,9 +101,9 @@ Error PacketPeer::put_var(const Variant &p_packet, bool p_full_objects) {
 		return OK;
 
 	uint8_t *buf = (uint8_t *)alloca(len);
-	ERR_FAIL_COND_V(!buf, ERR_OUT_OF_MEMORY);
+	ERR_FAIL_COND_V_MSG(!buf, ERR_OUT_OF_MEMORY, "Out of memory.");
 	err = encode_variant(p_packet, buf, len, p_full_objects || allow_object_decoding);
-	ERR_FAIL_COND_V(err, err);
+	ERR_FAIL_COND_V_MSG(err != OK, err, "Error when trying to encode Variant.");
 
 	return put_packet(buf, len);
 }
@@ -150,7 +150,7 @@ void PacketPeer::_bind_methods() {
 
 void PacketPeerStream::_set_stream_peer(REF p_peer) {
 
-	ERR_FAIL_COND(p_peer.is_null());
+	ERR_FAIL_COND_MSG(p_peer.is_null(), "It's not a reference to a valid Resource object.");
 	set_stream_peer(p_peer);
 }
 
diff --git a/core/io/pck_packer.cpp b/core/io/pck_packer.cpp
index 1c89bc6268..443f390bb7 100644
--- a/core/io/pck_packer.cpp
+++ b/core/io/pck_packer.cpp
@@ -107,7 +107,7 @@ Error PCKPacker::add_file(const String &p_file, const String &p_src) {
 
 Error PCKPacker::flush(bool p_verbose) {
 
-	ERR_FAIL_COND_V(!file, ERR_INVALID_PARAMETER);
+	ERR_FAIL_COND_V_MSG(!file, ERR_INVALID_PARAMETER, "File must be opened before use.");
 
 	// write the index
 
diff --git a/core/io/resource_format_binary.cpp b/core/io/resource_format_binary.cpp
index 0ad2479b05..e91dd579b5 100644
--- a/core/io/resource_format_binary.cpp
+++ b/core/io/resource_format_binary.cpp
@@ -378,10 +378,10 @@ Error ResourceInteractiveLoaderBinary::parse_variant(Variant &r_v) {
 			for (uint32_t i = 0; i < len; i++) {
 				Variant key;
 				Error err = parse_variant(key);
-				ERR_FAIL_COND_V(err, ERR_FILE_CORRUPT);
+				ERR_FAIL_COND_V_MSG(err, ERR_FILE_CORRUPT, "Error when trying to parse Variant.");
 				Variant value;
 				err = parse_variant(value);
-				ERR_FAIL_COND_V(err, ERR_FILE_CORRUPT);
+				ERR_FAIL_COND_V_MSG(err, ERR_FILE_CORRUPT, "Error when trying to parse Variant.");
 				d[key] = value;
 			}
 			r_v = d;
@@ -395,7 +395,7 @@ Error ResourceInteractiveLoaderBinary::parse_variant(Variant &r_v) {
 			for (uint32_t i = 0; i < len; i++) {
 				Variant val;
 				Error err = parse_variant(val);
-				ERR_FAIL_COND_V(err, ERR_FILE_CORRUPT);
+				ERR_FAIL_COND_V_MSG(err, ERR_FILE_CORRUPT, "Error when trying to parse Variant.");
 				a[i] = val;
 			}
 			r_v = a;
@@ -983,7 +983,7 @@ Ref<ResourceInteractiveLoader> ResourceFormatLoaderBinary::load_interactive(cons
 	Error err;
 	FileAccess *f = FileAccess::open(p_path, FileAccess::READ, &err);
 
-	ERR_FAIL_COND_V(err != OK, Ref<ResourceInteractiveLoader>());
+	ERR_FAIL_COND_V_MSG(err != OK, Ref<ResourceInteractiveLoader>(), "Cannot open file '" + p_path + "'.");
 
 	Ref<ResourceInteractiveLoaderBinary> ria = memnew(ResourceInteractiveLoaderBinary);
 	String path = p_original_path != "" ? p_original_path : p_path;
@@ -1032,7 +1032,7 @@ bool ResourceFormatLoaderBinary::handles_type(const String &p_type) const {
 void ResourceFormatLoaderBinary::get_dependencies(const String &p_path, List<String> *p_dependencies, bool p_add_types) {
 
 	FileAccess *f = FileAccess::open(p_path, FileAccess::READ);
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "Cannot open file '" + p_path + "'.");
 
 	Ref<ResourceInteractiveLoaderBinary> ria = memnew(ResourceInteractiveLoaderBinary);
 	ria->local_path = ProjectSettings::get_singleton()->localize_path(p_path);
@@ -1046,7 +1046,7 @@ Error ResourceFormatLoaderBinary::rename_dependencies(const String &p_path, cons
 	//Error error=OK;
 
 	FileAccess *f = FileAccess::open(p_path, FileAccess::READ);
-	ERR_FAIL_COND_V(!f, ERR_CANT_OPEN);
+	ERR_FAIL_COND_V_MSG(!f, ERR_CANT_OPEN, "Cannot open file '" + p_path + "'.");
 
 	FileAccess *fw = NULL; //=FileAccess::open(p_path+".depren");
 
@@ -1066,7 +1066,7 @@ Error ResourceFormatLoaderBinary::rename_dependencies(const String &p_path, cons
 		if (err) {
 			memdelete(fac);
 			memdelete(facw);
-			ERR_FAIL_COND_V(err, ERR_FILE_CORRUPT);
+			ERR_FAIL_COND_V_MSG(err, ERR_FILE_CORRUPT, "Cannot create file '" + p_path + ".depren'.");
 		}
 
 		fw = facw;
@@ -1076,13 +1076,13 @@ Error ResourceFormatLoaderBinary::rename_dependencies(const String &p_path, cons
 
 		//error=ERR_FILE_UNRECOGNIZED;
 		memdelete(f);
-		ERR_FAIL_V_MSG(ERR_FILE_UNRECOGNIZED, "Unrecognized binary resource file: " + local_path + ".");
+		ERR_FAIL_V_MSG(ERR_FILE_UNRECOGNIZED, "Unrecognized binary resource file '" + local_path + "'.");
 	} else {
 		fw = FileAccess::open(p_path + ".depren", FileAccess::WRITE);
 		if (!fw) {
 			memdelete(f);
 		}
-		ERR_FAIL_COND_V(!fw, ERR_CANT_CREATE);
+		ERR_FAIL_COND_V_MSG(!fw, ERR_CANT_CREATE, "Cannot create file '" + p_path + ".depren'.");
 
 		uint8_t magic[4] = { 'R', 'S', 'R', 'C' };
 		fw->store_buffer(magic, 4);
@@ -1113,12 +1113,12 @@ Error ResourceFormatLoaderBinary::rename_dependencies(const String &p_path, cons
 		memdelete(da);
 		//use the old approach
 
-		WARN_PRINTS("This file is old, so it can't refactor dependencies, opening and resaving: " + p_path + ".");
+		WARN_PRINTS("This file is old, so it can't refactor dependencies, opening and resaving '" + p_path + "'.");
 
 		Error err;
 		f = FileAccess::open(p_path, FileAccess::READ, &err);
 
-		ERR_FAIL_COND_V(err != OK, ERR_FILE_CANT_OPEN);
+		ERR_FAIL_COND_V_MSG(err != OK, ERR_FILE_CANT_OPEN, "Cannot open file '" + p_path + "'.");
 
 		Ref<ResourceInteractiveLoaderBinary> ria = memnew(ResourceInteractiveLoaderBinary);
 		ria->local_path = ProjectSettings::get_singleton()->localize_path(p_path);
@@ -1751,7 +1751,7 @@ Error ResourceFormatSaverBinaryInstance::save(const String &p_path, const RES &p
 		f = FileAccess::open(p_path, FileAccess::WRITE, &err);
 	}
 
-	ERR_FAIL_COND_V(err, err);
+	ERR_FAIL_COND_V_MSG(err != OK, err, "Cannot create file '" + p_path + "'.");
 
 	relative_paths = p_flags & ResourceSaver::FLAG_RELATIVE_PATHS;
 	skip_editor = p_flags & ResourceSaver::FLAG_OMIT_EDITOR_PROPERTIES;
diff --git a/core/io/resource_loader.cpp b/core/io/resource_loader.cpp
index 9e954890bc..f3eba44973 100644
--- a/core/io/resource_loader.cpp
+++ b/core/io/resource_loader.cpp
@@ -205,7 +205,7 @@ RES ResourceFormatLoader::load(const String &p_path, const String &p_original_pa
 		if (r_error)
 			*r_error = err;
 
-		ERR_FAIL_COND_V(err != OK, RES());
+		ERR_FAIL_COND_V_MSG(err != OK, RES(), "Failed to load resource '" + p_path + "'.");
 	}
 }
 
diff --git a/core/io/resource_saver.cpp b/core/io/resource_saver.cpp
index a9ad62afe6..7aa8732366 100644
--- a/core/io/resource_saver.cpp
+++ b/core/io/resource_saver.cpp
@@ -158,7 +158,7 @@ void ResourceSaver::get_recognized_extensions(const RES &p_resource, List<String
 
 void ResourceSaver::add_resource_format_saver(Ref<ResourceFormatSaver> p_format_saver, bool p_at_front) {
 
-	ERR_FAIL_COND(p_format_saver.is_null());
+	ERR_FAIL_COND_MSG(p_format_saver.is_null(), "It's not a reference to a valid ResourceFormatSaver object.");
 	ERR_FAIL_COND(saver_count >= MAX_SAVERS);
 
 	if (p_at_front) {
@@ -174,7 +174,7 @@ void ResourceSaver::add_resource_format_saver(Ref<ResourceFormatSaver> p_format_
 
 void ResourceSaver::remove_resource_format_saver(Ref<ResourceFormatSaver> p_format_saver) {
 
-	ERR_FAIL_COND(p_format_saver.is_null());
+	ERR_FAIL_COND_MSG(p_format_saver.is_null(), "It's not a reference to a valid ResourceFormatSaver object.");
 
 	// Find saver
 	int i = 0;
diff --git a/core/io/stream_peer.cpp b/core/io/stream_peer.cpp
index 84b8554d54..f19e055b64 100644
--- a/core/io/stream_peer.cpp
+++ b/core/io/stream_peer.cpp
@@ -370,7 +370,7 @@ Variant StreamPeer::get_var(bool p_allow_objects) {
 
 	Variant ret;
 	err = decode_variant(ret, var.ptr(), len, NULL, p_allow_objects);
-	ERR_FAIL_COND_V(err != OK, Variant());
+	ERR_FAIL_COND_V_MSG(err != OK, Variant(), "Error when trying to decode Variant.");
 
 	return ret;
 }
diff --git a/core/io/translation_loader_po.cpp b/core/io/translation_loader_po.cpp
index e8e71c10ca..9b6888ac21 100644
--- a/core/io/translation_loader_po.cpp
+++ b/core/io/translation_loader_po.cpp
@@ -182,7 +182,7 @@ RES TranslationLoaderPO::load(const String &p_path, const String &p_original_pat
 		*r_error = ERR_CANT_OPEN;
 
 	FileAccess *f = FileAccess::open(p_path, FileAccess::READ);
-	ERR_FAIL_COND_V(!f, RES());
+	ERR_FAIL_COND_V_MSG(!f, RES(), "Cannot open file '" + p_path + "'.");
 
 	return load_translation(f, r_error);
 }
diff --git a/core/io/xml_parser.cpp b/core/io/xml_parser.cpp
index 9487947365..575c78734f 100644
--- a/core/io/xml_parser.cpp
+++ b/core/io/xml_parser.cpp
@@ -484,7 +484,7 @@ Error XMLParser::open(const String &p_path) {
 	Error err;
 	FileAccess *file = FileAccess::open(p_path, FileAccess::READ, &err);
 
-	ERR_FAIL_COND_V(err != OK, err);
+	ERR_FAIL_COND_V_MSG(err != OK, err, "Cannot open file '" + p_path + "'.");
 
 	length = file->get_len();
 	ERR_FAIL_COND_V(length < 1, ERR_FILE_CORRUPT);
diff --git a/core/math/basis.cpp b/core/math/basis.cpp
index 2985959113..0a491010e2 100644
--- a/core/math/basis.cpp
+++ b/core/math/basis.cpp
@@ -807,7 +807,7 @@ void Basis::set_quat(const Quat &p_quat) {
 void Basis::set_axis_angle(const Vector3 &p_axis, real_t p_phi) {
 // Rotation matrix from axis and angle, see https://en.wikipedia.org/wiki/Rotation_matrix#Rotation_matrix_from_axis_angle
 #ifdef MATH_CHECKS
-	ERR_FAIL_COND(!p_axis.is_normalized());
+	ERR_FAIL_COND_MSG(!p_axis.is_normalized(), "Axis must be normalized.");
 #endif
 	Vector3 axis_sq(p_axis.x * p_axis.x, p_axis.y * p_axis.y, p_axis.z * p_axis.z);
 	real_t cosine = Math::cos(p_phi);
diff --git a/core/math/geometry.cpp b/core/math/geometry.cpp
index f37db90929..30cb736d68 100644
--- a/core/math/geometry.cpp
+++ b/core/math/geometry.cpp
@@ -241,10 +241,7 @@ PoolVector<PoolVector<Face3> > Geometry::separate_objects(PoolVector<Face3> p_ar
 
 	bool error = _connect_faces(_fcptr, len, -1);
 
-	if (error) {
-
-		ERR_FAIL_COND_V(error, PoolVector<PoolVector<Face3> >()); // Invalid geometry.
-	}
+	ERR_FAIL_COND_V_MSG(error, PoolVector<PoolVector<Face3> >(), "Invalid geometry.");
 
 	// Group connected faces in separate objects.
 
diff --git a/core/message_queue.cpp b/core/message_queue.cpp
index 390989ac91..a76b5167b6 100644
--- a/core/message_queue.cpp
+++ b/core/message_queue.cpp
@@ -340,7 +340,7 @@ bool MessageQueue::is_flushing() const {
 
 MessageQueue::MessageQueue() {
 
-	ERR_FAIL_COND(singleton != NULL);
+	ERR_FAIL_COND_MSG(singleton != NULL, "MessageQueue singleton already exist.");
 	singleton = this;
 	flushing = false;
 
diff --git a/core/node_path.cpp b/core/node_path.cpp
index 8244785d84..b43f76f680 100644
--- a/core/node_path.cpp
+++ b/core/node_path.cpp
@@ -375,7 +375,7 @@ NodePath::NodePath(const String &p_path) {
 				if (str == "") {
 					if (path[i] == 0) continue; // Allow end-of-path :
 
-					ERR_FAIL_MSG("Invalid NodePath: " + p_path + ".");
+					ERR_FAIL_MSG("Invalid NodePath '" + p_path + "'.");
 				}
 				subpath.push_back(str);
 
diff --git a/core/object.cpp b/core/object.cpp
index 62bfa31480..6facf38733 100644
--- a/core/object.cpp
+++ b/core/object.cpp
@@ -1100,9 +1100,9 @@ void Object::get_meta_list(List<String> *p_list) const {
 
 void Object::add_user_signal(const MethodInfo &p_signal) {
 
-	ERR_FAIL_COND(p_signal.name == "");
-	ERR_FAIL_COND(ClassDB::has_signal(get_class_name(), p_signal.name));
-	ERR_FAIL_COND(signal_map.has(p_signal.name));
+	ERR_FAIL_COND_MSG(p_signal.name == "", "Signal name cannot be empty.");
+	ERR_FAIL_COND_MSG(ClassDB::has_signal(get_class_name(), p_signal.name), "User signal's name conflicts with a built-in signal of '" + get_class_name() + "'.");
+	ERR_FAIL_COND_MSG(signal_map.has(p_signal.name), "Trying to add already existing signal '" + p_signal.name + "'.");
 	Signal s;
 	s.user = p_signal;
 	signal_map[p_signal.name] = s;
diff --git a/core/os/dir_access.cpp b/core/os/dir_access.cpp
index b444f0ae1e..e7496055ec 100644
--- a/core/os/dir_access.cpp
+++ b/core/os/dir_access.cpp
@@ -244,7 +244,7 @@ DirAccess *DirAccess::open(const String &p_path, Error *r_error) {
 
 	DirAccess *da = create_for_path(p_path);
 
-	ERR_FAIL_COND_V(!da, NULL);
+	ERR_FAIL_COND_V_MSG(!da, NULL, "Cannot create DirAccess for path '" + p_path + "'.");
 	Error err = da->change_dir(p_path);
 	if (r_error)
 		*r_error = err;
@@ -384,39 +384,36 @@ Error DirAccess::_copy_dir(DirAccess *p_target_da, String p_to, int p_chmod_flag
 		String target_dir = p_to + rel_path;
 		if (!p_target_da->dir_exists(target_dir)) {
 			Error err = p_target_da->make_dir(target_dir);
-			ERR_FAIL_COND_V(err, err);
+			ERR_FAIL_COND_V_MSG(err != OK, err, "Cannot create directory '" + target_dir + "'.");
 		}
 
 		Error err = change_dir(E->get());
-		ERR_FAIL_COND_V(err, err);
+		ERR_FAIL_COND_V_MSG(err != OK, err, "Cannot change current directory to '" + E->get() + "'.");
+
 		err = _copy_dir(p_target_da, p_to + rel_path + "/", p_chmod_flags);
 		if (err) {
 			change_dir("..");
-			ERR_PRINT("Failed to copy recursively");
-			return err;
+			ERR_FAIL_V_MSG(err, "Failed to copy recursively.");
 		}
 		err = change_dir("..");
-		if (err) {
-			ERR_PRINT("Failed to go back");
-			return err;
-		}
+		ERR_FAIL_COND_V_MSG(err != OK, err, "Failed to go back.");
 	}
 
 	return OK;
 }
 
 Error DirAccess::copy_dir(String p_from, String p_to, int p_chmod_flags) {
-	ERR_FAIL_COND_V(!dir_exists(p_from), ERR_FILE_NOT_FOUND);
+	ERR_FAIL_COND_V_MSG(!dir_exists(p_from), ERR_FILE_NOT_FOUND, "Source directory doesn't exist.");
 
 	DirAccess *target_da = DirAccess::create_for_path(p_to);
-	ERR_FAIL_COND_V(!target_da, ERR_CANT_CREATE);
+	ERR_FAIL_COND_V_MSG(!target_da, ERR_CANT_CREATE, "Cannot create DirAccess for path '" + p_to + "'.");
 
 	if (!target_da->dir_exists(p_to)) {
 		Error err = target_da->make_dir_recursive(p_to);
 		if (err) {
 			memdelete(target_da);
 		}
-		ERR_FAIL_COND_V(err, err);
+		ERR_FAIL_COND_V_MSG(err != OK, err, "Cannot create directory '" + p_to + "'.");
 	}
 
 	if (!p_to.ends_with("/")) {
diff --git a/core/os/file_access.cpp b/core/os/file_access.cpp
index 9a8315a3bb..738e597730 100644
--- a/core/os/file_access.cpp
+++ b/core/os/file_access.cpp
@@ -498,7 +498,7 @@ uint64_t FileAccess::get_modified_time(const String &p_file) {
 		return 0;
 
 	FileAccess *fa = create_for_path(p_file);
-	ERR_FAIL_COND_V(!fa, 0);
+	ERR_FAIL_COND_V_MSG(!fa, 0, "Cannot create FileAccess for path '" + p_file + "'.");
 
 	uint64_t mt = fa->_get_modified_time(p_file);
 	memdelete(fa);
@@ -511,7 +511,7 @@ uint32_t FileAccess::get_unix_permissions(const String &p_file) {
 		return 0;
 
 	FileAccess *fa = create_for_path(p_file);
-	ERR_FAIL_COND_V(!fa, 0);
+	ERR_FAIL_COND_V_MSG(!fa, 0, "Cannot create FileAccess for path '" + p_file + "'.");
 
 	uint32_t mt = fa->_get_unix_permissions(p_file);
 	memdelete(fa);
@@ -521,7 +521,7 @@ uint32_t FileAccess::get_unix_permissions(const String &p_file) {
 Error FileAccess::set_unix_permissions(const String &p_file, uint32_t p_permissions) {
 
 	FileAccess *fa = create_for_path(p_file);
-	ERR_FAIL_COND_V(!fa, ERR_CANT_CREATE);
+	ERR_FAIL_COND_V_MSG(!fa, ERR_CANT_CREATE, "Cannot create FileAccess for path '" + p_file + "'.");
 
 	Error err = fa->_set_unix_permissions(p_file, p_permissions);
 	memdelete(fa);
@@ -599,7 +599,7 @@ Vector<uint8_t> FileAccess::get_file_as_array(const String &p_path, Error *r_err
 		if (r_error) { // if error requested, do not throw error
 			return Vector<uint8_t>();
 		}
-		ERR_FAIL_V_MSG(Vector<uint8_t>(), "Can't open file from path: " + String(p_path) + ".");
+		ERR_FAIL_V_MSG(Vector<uint8_t>(), "Can't open file from path '" + String(p_path) + "'.");
 	}
 	Vector<uint8_t> data;
 	data.resize(f->get_len());
@@ -619,7 +619,7 @@ String FileAccess::get_file_as_string(const String &p_path, Error *r_error) {
 		if (r_error) {
 			return String();
 		}
-		ERR_FAIL_V_MSG(String(), "Can't get file as string from path: " + String(p_path) + ".");
+		ERR_FAIL_V_MSG(String(), "Can't get file as string from path '" + String(p_path) + "'.");
 	}
 
 	String ret;
diff --git a/core/os/os.cpp b/core/os/os.cpp
index 7531900480..b44487b908 100644
--- a/core/os/os.cpp
+++ b/core/os/os.cpp
@@ -722,7 +722,7 @@ int OS::get_audio_driver_count() const {
 const char *OS::get_audio_driver_name(int p_driver) const {
 
 	AudioDriver *driver = AudioDriverManager::get_driver(p_driver);
-	ERR_FAIL_COND_V(!driver, "");
+	ERR_FAIL_COND_V_MSG(!driver, "", "Cannot get audio driver at index '" + itos(p_driver) + "'.");
 	return AudioDriverManager::get_driver(p_driver)->get_name();
 }
 
diff --git a/core/packed_data_container.cpp b/core/packed_data_container.cpp
index 54bf12b314..003e7e7428 100644
--- a/core/packed_data_container.cpp
+++ b/core/packed_data_container.cpp
@@ -119,7 +119,7 @@ Variant PackedDataContainer::_get_at_ofs(uint32_t p_ofs, const uint8_t *p_buf, b
 		if (rerr != OK) {
 
 			err = true;
-			ERR_FAIL_COND_V(err != OK, Variant());
+			ERR_FAIL_COND_V_MSG(err != OK, Variant(), "Error when trying to decode Variant.");
 		}
 		return v;
 	}
diff --git a/core/pool_vector.h b/core/pool_vector.h
index 957a72483c..fbd4d630be 100644
--- a/core/pool_vector.h
+++ b/core/pool_vector.h
@@ -508,7 +508,7 @@ T PoolVector<T>::operator[](int p_index) const {
 template <class T>
 Error PoolVector<T>::resize(int p_size) {
 
-	ERR_FAIL_COND_V(p_size < 0, ERR_INVALID_PARAMETER);
+	ERR_FAIL_COND_V_MSG(p_size < 0, ERR_INVALID_PARAMETER, "Size of PoolVector cannot be negative.");
 
 	if (alloc == NULL) {
 
@@ -536,7 +536,7 @@ Error PoolVector<T>::resize(int p_size) {
 
 	} else {
 
-		ERR_FAIL_COND_V(alloc->lock > 0, ERR_LOCKED); //can't resize if locked!
+		ERR_FAIL_COND_V_MSG(alloc->lock > 0, ERR_LOCKED, "Can't resize PoolVector if locked."); //can't resize if locked!
 	}
 
 	size_t new_size = sizeof(T) * p_size;
diff --git a/core/project_settings.cpp b/core/project_settings.cpp
index ec2c5ecbb3..9e3b9bd1e4 100644
--- a/core/project_settings.cpp
+++ b/core/project_settings.cpp
@@ -113,12 +113,12 @@ String ProjectSettings::localize_path(const String &p_path) const {
 
 void ProjectSettings::set_initial_value(const String &p_name, const Variant &p_value) {
 
-	ERR_FAIL_COND(!props.has(p_name));
+	ERR_FAIL_COND_MSG(!props.has(p_name), "Request for nonexistent project setting: " + p_name + ".");
 	props[p_name].initial = p_value;
 }
 void ProjectSettings::set_restart_if_changed(const String &p_name, bool p_restart) {
 
-	ERR_FAIL_COND(!props.has(p_name));
+	ERR_FAIL_COND_MSG(!props.has(p_name), "Request for nonexistent project setting: " + p_name + ".");
 	props[p_name].restart_if_changed = p_restart;
 }
 
@@ -336,7 +336,7 @@ Error ProjectSettings::_setup(const String &p_path, const String &p_main_pack, b
 	if (p_main_pack != "") {
 
 		bool ok = _load_resource_pack(p_main_pack);
-		ERR_FAIL_COND_V(!ok, ERR_CANT_OPEN);
+		ERR_FAIL_COND_V_MSG(!ok, ERR_CANT_OPEN, "Cannot open resource pack '" + p_main_pack + "'.");
 
 		Error err = _load_settings_text_or_binary("res://project.godot", "res://project.binary");
 		if (err == OK) {
@@ -421,7 +421,7 @@ Error ProjectSettings::_setup(const String &p_path, const String &p_main_pack, b
 	// or, if requested (`p_upwards`) in parent directories.
 
 	DirAccess *d = DirAccess::create(DirAccess::ACCESS_FILESYSTEM);
-	ERR_FAIL_COND_V(!d, ERR_CANT_CREATE);
+	ERR_FAIL_COND_V_MSG(!d, ERR_CANT_CREATE, "Cannot create DirAccess for path '" + p_path + "'.");
 	d->change_dir(p_path);
 
 	String current_dir = d->get_current_dir();
@@ -609,19 +609,19 @@ Error ProjectSettings::_load_settings_text_or_binary(const String &p_text_path,
 
 int ProjectSettings::get_order(const String &p_name) const {
 
-	ERR_FAIL_COND_V(!props.has(p_name), -1);
+	ERR_FAIL_COND_V_MSG(!props.has(p_name), -1, "Request for nonexistent project setting: " + p_name + ".");
 	return props[p_name].order;
 }
 
 void ProjectSettings::set_order(const String &p_name, int p_order) {
 
-	ERR_FAIL_COND(!props.has(p_name));
+	ERR_FAIL_COND_MSG(!props.has(p_name), "Request for nonexistent project setting: " + p_name + ".");
 	props[p_name].order = p_order;
 }
 
 void ProjectSettings::set_builtin_order(const String &p_name) {
 
-	ERR_FAIL_COND(!props.has(p_name));
+	ERR_FAIL_COND_MSG(!props.has(p_name), "Request for nonexistent project setting: " + p_name + ".");
 	if (props[p_name].order >= NO_BUILTIN_ORDER_BASE) {
 		props[p_name].order = last_builtin_order++;
 	}
@@ -629,7 +629,7 @@ void ProjectSettings::set_builtin_order(const String &p_name) {
 
 void ProjectSettings::clear(const String &p_name) {
 
-	ERR_FAIL_COND(!props.has(p_name));
+	ERR_FAIL_COND_MSG(!props.has(p_name), "Request for nonexistent project setting: " + p_name + ".");
 	props.erase(p_name);
 }
 
@@ -706,7 +706,7 @@ Error ProjectSettings::_save_settings_binary(const String &p_file, const Map<Str
 			err = encode_variant(value, NULL, len, true);
 			if (err != OK)
 				memdelete(file);
-			ERR_FAIL_COND_V(err != OK, ERR_INVALID_DATA);
+			ERR_FAIL_COND_V_MSG(err != OK, ERR_INVALID_DATA, "Error when trying to encode Variant.");
 
 			Vector<uint8_t> buff;
 			buff.resize(len);
@@ -714,7 +714,7 @@ Error ProjectSettings::_save_settings_binary(const String &p_file, const Map<Str
 			err = encode_variant(value, buff.ptrw(), len, true);
 			if (err != OK)
 				memdelete(file);
-			ERR_FAIL_COND_V(err != OK, ERR_INVALID_DATA);
+			ERR_FAIL_COND_V_MSG(err != OK, ERR_INVALID_DATA, "Error when trying to encode Variant.");
 			file->store_32(len);
 			file->store_buffer(buff.ptr(), buff.size());
 		}
@@ -787,7 +787,7 @@ Error ProjectSettings::_save_custom_bnd(const String &p_file) { // add other par
 
 Error ProjectSettings::save_custom(const String &p_path, const CustomMap &p_custom, const Vector<String> &p_custom_features, bool p_merge_with_current) {
 
-	ERR_FAIL_COND_V(p_path == "", ERR_INVALID_PARAMETER);
+	ERR_FAIL_COND_V_MSG(p_path == "", ERR_INVALID_PARAMETER, "Project settings save path cannot be empty.");
 
 	Set<_VCSort> vclist;
 
diff --git a/core/resource.cpp b/core/resource.cpp
index 5a5efa4644..87c92ca5b1 100644
--- a/core/resource.cpp
+++ b/core/resource.cpp
@@ -75,7 +75,7 @@ void Resource::set_path(const String &p_path, bool p_take_over) {
 			bool exists = ResourceCache::resources.has(p_path);
 			ResourceCache::lock->read_unlock();
 
-			ERR_FAIL_COND_MSG(exists, "Another resource is loaded from path: " + p_path + " (possible cyclic resource inclusion).");
+			ERR_FAIL_COND_MSG(exists, "Another resource is loaded from path '" + p_path + "' (possible cyclic resource inclusion).");
 		}
 	}
 	path_cache = p_path;
@@ -509,7 +509,7 @@ void ResourceCache::dump(const char *p_file, bool p_short) {
 	FileAccess *f = NULL;
 	if (p_file) {
 		f = FileAccess::open(p_file, FileAccess::WRITE);
-		ERR_FAIL_COND(!f);
+		ERR_FAIL_COND_MSG(!f, "Cannot create file at path '" + String(p_file) + "'.");
 	}
 
 	const String *K = NULL;
diff --git a/drivers/dummy/rasterizer_dummy.h b/drivers/dummy/rasterizer_dummy.h
index 3deaef09e7..8d5cf2ebea 100644
--- a/drivers/dummy/rasterizer_dummy.h
+++ b/drivers/dummy/rasterizer_dummy.h
@@ -181,8 +181,8 @@ public:
 		DummyTexture *t = texture_owner.get(p_texture);
 
 		ERR_FAIL_COND(!t);
+		ERR_FAIL_COND_MSG(p_image.is_null(), "It's not a reference to a valid Image object.");
 		ERR_FAIL_COND(t->format != p_image->get_format());
-		ERR_FAIL_COND(p_image.is_null());
 		ERR_FAIL_COND(src_w <= 0 || src_h <= 0);
 		ERR_FAIL_COND(src_x < 0 || src_y < 0 || src_x + src_w > p_image->get_width() || src_y + src_h > p_image->get_height());
 		ERR_FAIL_COND(dst_x < 0 || dst_y < 0 || dst_x + src_w > t->width || dst_y + src_h > t->height);
diff --git a/drivers/unix/file_access_unix.cpp b/drivers/unix/file_access_unix.cpp
index 071734eb48..8be1d5d8f3 100644
--- a/drivers/unix/file_access_unix.cpp
+++ b/drivers/unix/file_access_unix.cpp
@@ -58,7 +58,7 @@
 
 void FileAccessUnix::check_errors() const {
 
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
 
 	if (feof(f)) {
 
@@ -76,7 +76,7 @@ Error FileAccessUnix::_open(const String &p_path, int p_mode_flags) {
 	path = fix_path(p_path);
 	//printf("opening %ls, %i\n", path.c_str(), Memory::get_static_mem_usage());
 
-	ERR_FAIL_COND_V(f, ERR_ALREADY_IN_USE);
+	ERR_FAIL_COND_V_MSG(f, ERR_ALREADY_IN_USE, "File is already in use.");
 	const char *mode_string;
 
 	if (p_mode_flags == READ)
@@ -171,7 +171,7 @@ String FileAccessUnix::get_path_absolute() const {
 
 void FileAccessUnix::seek(size_t p_position) {
 
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
 
 	last_error = OK;
 	if (fseek(f, p_position, SEEK_SET))
@@ -180,7 +180,7 @@ void FileAccessUnix::seek(size_t p_position) {
 
 void FileAccessUnix::seek_end(int64_t p_position) {
 
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
 
 	if (fseek(f, p_position, SEEK_END))
 		check_errors();
@@ -188,7 +188,7 @@ void FileAccessUnix::seek_end(int64_t p_position) {
 
 size_t FileAccessUnix::get_position() const {
 
-	ERR_FAIL_COND_V(!f, 0);
+	ERR_FAIL_COND_V_MSG(!f, 0, "File must be opened before use.");
 
 	long pos = ftell(f);
 	if (pos < 0) {
@@ -200,7 +200,7 @@ size_t FileAccessUnix::get_position() const {
 
 size_t FileAccessUnix::get_len() const {
 
-	ERR_FAIL_COND_V(!f, 0);
+	ERR_FAIL_COND_V_MSG(!f, 0, "File must be opened before use.");
 
 	long pos = ftell(f);
 	ERR_FAIL_COND_V(pos < 0, 0);
@@ -219,7 +219,7 @@ bool FileAccessUnix::eof_reached() const {
 
 uint8_t FileAccessUnix::get_8() const {
 
-	ERR_FAIL_COND_V(!f, 0);
+	ERR_FAIL_COND_V_MSG(!f, 0, "File must be opened before use.");
 	uint8_t b;
 	if (fread(&b, 1, 1, f) == 0) {
 		check_errors();
@@ -230,7 +230,7 @@ uint8_t FileAccessUnix::get_8() const {
 
 int FileAccessUnix::get_buffer(uint8_t *p_dst, int p_length) const {
 
-	ERR_FAIL_COND_V(!f, -1);
+	ERR_FAIL_COND_V_MSG(!f, -1, "File must be opened before use.");
 	int read = fread(p_dst, 1, p_length, f);
 	check_errors();
 	return read;
@@ -243,18 +243,19 @@ Error FileAccessUnix::get_error() const {
 
 void FileAccessUnix::flush() {
 
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
 	fflush(f);
 }
 
 void FileAccessUnix::store_8(uint8_t p_dest) {
 
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
 	ERR_FAIL_COND(fwrite(&p_dest, 1, 1, f) != 1);
 }
 
 void FileAccessUnix::store_buffer(const uint8_t *p_src, int p_length) {
-	ERR_FAIL_COND(!f);
+
+	ERR_FAIL_COND_MSG(!f, "File must be opened before use.");
 	ERR_FAIL_COND((int)fwrite(p_src, 1, p_length, f) != p_length);
 }
 
diff --git a/drivers/unix/os_unix.cpp b/drivers/unix/os_unix.cpp
index ab5590dba4..bc57c0b8df 100644
--- a/drivers/unix/os_unix.cpp
+++ b/drivers/unix/os_unix.cpp
@@ -298,7 +298,7 @@ Error OS_Unix::execute(const String &p_path, const List<String> &p_arguments, bo
 		}
 		FILE *f = popen(argss.utf8().get_data(), "r");
 
-		ERR_FAIL_COND_V(!f, ERR_CANT_OPEN);
+		ERR_FAIL_COND_V_MSG(!f, ERR_CANT_OPEN, "Cannot pipe stream from process running with following arguments '" + argss + "'.");
 
 		char buf[65535];
 
diff --git a/editor/collada/collada.cpp b/editor/collada/collada.cpp
index 1bb49a4167..d2ecf0f7f3 100644
--- a/editor/collada/collada.cpp
+++ b/editor/collada/collada.cpp
@@ -2514,7 +2514,7 @@ Error Collada::load(const String &p_path, int p_flags) {
 	Ref<XMLParser> parserr = memnew(XMLParser);
 	XMLParser &parser = *parserr.ptr();
 	Error err = parser.open(p_path);
-	ERR_FAIL_COND_V(err, err);
+	ERR_FAIL_COND_V_MSG(err, err, "Cannot open Collada file '" + p_path + "'.");
 
 	state.local_path = ProjectSettings::get_singleton()->localize_path(p_path);
 	state.import_flags = p_flags;
@@ -2530,7 +2530,7 @@ Error Collada::load(const String &p_path, int p_flags) {
 		}
 	}
 
-	ERR_FAIL_COND_V(err != OK, ERR_FILE_CORRUPT);
+	ERR_FAIL_COND_V_MSG(err != OK, ERR_FILE_CORRUPT, "Corrupted Collada file '" + p_path + "'.");
 
 	/* Start loading Collada */
 
diff --git a/editor/editor_data.cpp b/editor/editor_data.cpp
index c98635d16b..777eda2170 100644
--- a/editor/editor_data.cpp
+++ b/editor/editor_data.cpp
@@ -481,7 +481,7 @@ EditorPlugin *EditorData::get_editor_plugin(int p_idx) {
 
 void EditorData::add_custom_type(const String &p_type, const String &p_inherits, const Ref<Script> &p_script, const Ref<Texture> &p_icon) {
 
-	ERR_FAIL_COND(p_script.is_null());
+	ERR_FAIL_COND_MSG(p_script.is_null(), "It's not a reference to a valid Script object.");
 	CustomType ct;
 	ct.name = p_type;
 	ct.icon = p_icon;
diff --git a/editor/editor_dir_dialog.cpp b/editor/editor_dir_dialog.cpp
index 7733ecb9da..0636ae3aea 100644
--- a/editor/editor_dir_dialog.cpp
+++ b/editor/editor_dir_dialog.cpp
@@ -151,7 +151,7 @@ void EditorDirDialog::_make_dir_confirm() {
 	String dir = ti->get_metadata(0);
 
 	DirAccessRef d = DirAccess::open(dir);
-	ERR_FAIL_COND(!d);
+	ERR_FAIL_COND_MSG(!d, "Cannot open directory '" + dir + "'.");
 	Error err = d->make_dir(makedirname->get_text());
 
 	if (err != OK) {
diff --git a/editor/editor_export.cpp b/editor/editor_export.cpp
index e58c7c992a..90f54df485 100644
--- a/editor/editor_export.cpp
+++ b/editor/editor_export.cpp
@@ -913,7 +913,7 @@ Error EditorExportPlatform::save_pack(const Ref<EditorExportPreset> &p_preset, c
 
 	String tmppath = EditorSettings::get_singleton()->get_cache_dir().plus_file("packtmp");
 	FileAccess *ftmp = FileAccess::open(tmppath, FileAccess::WRITE);
-	ERR_FAIL_COND_V(!ftmp, ERR_CANT_CREATE);
+	ERR_FAIL_COND_V_MSG(!ftmp, ERR_CANT_CREATE, "Cannot create file '" + tmppath + "'.");
 
 	PackData pd;
 	pd.ep = &ep;
@@ -1017,7 +1017,7 @@ Error EditorExportPlatform::save_pack(const Ref<EditorExportPreset> &p_preset, c
 	if (!ftmp) {
 		memdelete(f);
 		DirAccess::remove_file_or_error(tmppath);
-		ERR_FAIL_V_MSG(ERR_CANT_CREATE, "Can't open file to read from path: " + String(tmppath) + ".");
+		ERR_FAIL_V_MSG(ERR_CANT_CREATE, "Can't open file to read from path '" + String(tmppath) + "'.");
 	}
 
 	const int bufsize = 16384;
diff --git a/editor/editor_feature_profile.cpp b/editor/editor_feature_profile.cpp
index c6646eb28b..145931439a 100644
--- a/editor/editor_feature_profile.cpp
+++ b/editor/editor_feature_profile.cpp
@@ -165,7 +165,7 @@ Error EditorFeatureProfile::save_to_file(const String &p_path) {
 	json["disabled_features"] = dis_features;
 
 	FileAccessRef f = FileAccess::open(p_path, FileAccess::WRITE);
-	ERR_FAIL_COND_V(!f, ERR_CANT_OPEN);
+	ERR_FAIL_COND_V_MSG(!f, ERR_CANT_CREATE, "Cannot create file '" + p_path + "'.");
 
 	String text = JSON::print(json, "\t");
 	f->store_string(text);
@@ -326,7 +326,8 @@ void EditorFeatureProfileManager::_update_profile_list(const String &p_select_pr
 
 	Vector<String> profiles;
 	DirAccessRef d = DirAccess::open(EditorSettings::get_singleton()->get_feature_profiles_dir());
-	ERR_FAIL_COND(!d);
+	ERR_FAIL_COND_MSG(!d, "Cannot open directory '" + EditorSettings::get_singleton()->get_feature_profiles_dir() + "'.");
+
 	d->list_dir_begin();
 	while (true) {
 		String f = d->get_next();
@@ -433,7 +434,8 @@ void EditorFeatureProfileManager::_erase_selected_profile() {
 	String selected = _get_selected_profile();
 	ERR_FAIL_COND(selected == String());
 	DirAccessRef da = DirAccess::open(EditorSettings::get_singleton()->get_feature_profiles_dir());
-	ERR_FAIL_COND(!da);
+	ERR_FAIL_COND_MSG(!da, "Cannot open directory '" + EditorSettings::get_singleton()->get_feature_profiles_dir() + "'.");
+
 	da->remove(selected + ".profile");
 	if (selected == current_profile) {
 		_profile_action(PROFILE_CLEAR);
@@ -672,7 +674,7 @@ void EditorFeatureProfileManager::_update_selected_profile() {
 		//reload edited, if different from current
 		edited.instance();
 		Error err = edited->load_from_file(EditorSettings::get_singleton()->get_feature_profiles_dir().plus_file(profile + ".profile"));
-		ERR_FAIL_COND(err != OK);
+		ERR_FAIL_COND_MSG(err != OK, "Error when loading EditorSettings from file '" + EditorSettings::get_singleton()->get_feature_profiles_dir().plus_file(profile + ".profile") + "'.");
 	}
 
 	updating_features = true;
diff --git a/editor/editor_file_system.cpp b/editor/editor_file_system.cpp
index 6d3377a85b..3663bdee27 100644
--- a/editor/editor_file_system.cpp
+++ b/editor/editor_file_system.cpp
@@ -326,7 +326,7 @@ void EditorFileSystem::_save_filesystem_cache() {
 
 	FileAccess *f = FileAccess::open(fscache, FileAccess::WRITE);
 	if (f == NULL) {
-		ERR_PRINTS("Error writing fscache: " + fscache);
+		ERR_PRINTS("Error writing fscache '" + fscache + "'.");
 	} else {
 		f->store_line(filesystem_settings_version_for_import);
 		_save_filesystem_cache(filesystem, f);
@@ -389,7 +389,7 @@ bool EditorFileSystem::_test_for_reimport(const String &p_path, bool p_only_impo
 		if (err == ERR_FILE_EOF) {
 			break;
 		} else if (err != OK) {
-			ERR_PRINTS("ResourceFormatImporter::load - " + p_path + ".import:" + itos(lines) + " error: " + error_text);
+			ERR_PRINTS("ResourceFormatImporter::load - '" + p_path + ".import:" + itos(lines) + "' error '" + error_text + "'.");
 			memdelete(f);
 			return false; //parse error, try reimport manually (Avoid reimport loop on broken file)
 		}
@@ -437,7 +437,7 @@ bool EditorFileSystem::_test_for_reimport(const String &p_path, bool p_only_impo
 		if (err == ERR_FILE_EOF) {
 			break;
 		} else if (err != OK) {
-			ERR_PRINTS("ResourceFormatImporter::load - " + p_path + ".import.md5:" + itos(lines) + " error: " + error_text);
+			ERR_PRINTS("ResourceFormatImporter::load - '" + p_path + ".import.md5:" + itos(lines) + "' error '" + error_text + "'.");
 			memdelete(md5s);
 			return false; // parse error
 		}
@@ -736,7 +736,7 @@ void EditorFileSystem::_scan_new_dir(EditorFileSystemDirectory *p_dir, DirAccess
 				da->change_dir("..");
 			}
 		} else {
-			ERR_PRINTS("Cannot go into subdir: " + E->get());
+			ERR_PRINTS("Cannot go into subdir '" + E->get() + "'.");
 		}
 
 		p_progress.update(idx, total);
@@ -1555,7 +1555,7 @@ Error EditorFileSystem::_reimport_group(const String &p_group_file, const Vector
 		ERR_CONTINUE(file_importer_name == String());
 
 		if (importer_name != String() && importer_name != file_importer_name) {
-			print_line("one importer: " + importer_name + " the other: " + file_importer_name);
+			print_line("one importer '" + importer_name + "' the other '" + file_importer_name + "'.");
 			EditorNode::get_singleton()->show_warning(vformat(TTR("There are multiple importers for different types pointing to file %s, import aborted"), p_group_file));
 			ERR_FAIL_V(ERR_FILE_CORRUPT);
 		}
@@ -1599,7 +1599,7 @@ Error EditorFileSystem::_reimport_group(const String &p_group_file, const Vector
 		const String &file = E->key();
 		String base_path = ResourceFormatImporter::get_singleton()->get_import_base_path(file);
 		FileAccessRef f = FileAccess::open(file + ".import", FileAccess::WRITE);
-		ERR_FAIL_COND_V(!f, ERR_FILE_CANT_OPEN);
+		ERR_FAIL_COND_V_MSG(!f, ERR_FILE_CANT_OPEN, "Cannot open import file '" + file + ".import'.");
 
 		//write manually, as order matters ([remap] has to go first for performance).
 		f->store_line("[remap]");
@@ -1660,7 +1660,7 @@ Error EditorFileSystem::_reimport_group(const String &p_group_file, const Vector
 
 		// Store the md5's of the various files. These are stored separately so that the .import files can be version controlled.
 		FileAccessRef md5s = FileAccess::open(base_path + ".md5", FileAccess::WRITE);
-		ERR_FAIL_COND_V(!md5s, ERR_FILE_CANT_OPEN);
+		ERR_FAIL_COND_V_MSG(!md5s, ERR_FILE_CANT_OPEN, "Cannot open MD5 file '" + base_path + ".md5'.");
 
 		md5s->store_line("source_md5=\"" + FileAccess::get_md5(file) + "\"");
 		if (dest_paths.size()) {
@@ -1671,7 +1671,7 @@ Error EditorFileSystem::_reimport_group(const String &p_group_file, const Vector
 		EditorFileSystemDirectory *fs = NULL;
 		int cpos = -1;
 		bool found = _find_file(file, &fs, cpos);
-		ERR_FAIL_COND_V(!found, ERR_UNCONFIGURED);
+		ERR_FAIL_COND_V_MSG(!found, ERR_UNCONFIGURED, "Can't find file '" + file + "'.");
 
 		//update modified times, to avoid reimport
 		fs->files[cpos]->modified_time = FileAccess::get_modified_time(file);
@@ -1705,7 +1705,7 @@ void EditorFileSystem::_reimport_file(const String &p_file) {
 	EditorFileSystemDirectory *fs = NULL;
 	int cpos = -1;
 	bool found = _find_file(p_file, &fs, cpos);
-	ERR_FAIL_COND(!found);
+	ERR_FAIL_COND_MSG(!found, "Can't find file '" + p_file + "'.");
 
 	//try to obtain existing params
 
@@ -1781,13 +1781,13 @@ void EditorFileSystem::_reimport_file(const String &p_file) {
 	Error err = importer->import(p_file, base_path, params, &import_variants, &gen_files, &metadata);
 
 	if (err != OK) {
-		ERR_PRINTS("Error importing: " + p_file);
+		ERR_PRINTS("Error importing '" + p_file + "'.");
 	}
 
 	//as import is complete, save the .import file
 
 	FileAccess *f = FileAccess::open(p_file + ".import", FileAccess::WRITE);
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "Cannot open file from path '" + p_file + ".import'.");
 
 	//write manually, as order matters ([remap] has to go first for performance).
 	f->store_line("[remap]");
@@ -1872,7 +1872,8 @@ void EditorFileSystem::_reimport_file(const String &p_file) {
 
 	// Store the md5's of the various files. These are stored separately so that the .import files can be version controlled.
 	FileAccess *md5s = FileAccess::open(base_path + ".md5", FileAccess::WRITE);
-	ERR_FAIL_COND(!md5s);
+	ERR_FAIL_COND_MSG(!md5s, "Cannot open MD5 file '" + base_path + ".md5'.");
+
 	md5s->store_line("source_md5=\"" + FileAccess::get_md5(p_file) + "\"");
 	if (dest_paths.size()) {
 		md5s->store_line("dest_md5=\"" + FileAccess::get_multiple_md5(dest_paths) + "\"\n");
diff --git a/editor/editor_inspector.cpp b/editor/editor_inspector.cpp
index a76d34e122..7ffd62e909 100644
--- a/editor/editor_inspector.cpp
+++ b/editor/editor_inspector.cpp
@@ -1290,7 +1290,7 @@ void EditorInspector::remove_inspector_plugin(const Ref<EditorInspectorPlugin> &
 		}
 	}
 
-	ERR_FAIL_COND(idx == -1);
+	ERR_FAIL_COND_MSG(idx == -1, "Trying to remove nonexistent inspector plugin.");
 	for (int i = idx; i < inspector_plugin_count - 1; i++) {
 		inspector_plugins[i] = inspector_plugins[i + 1];
 	}
diff --git a/editor/editor_node.cpp b/editor/editor_node.cpp
index a1998a1d7c..842c06dded 100644
--- a/editor/editor_node.cpp
+++ b/editor/editor_node.cpp
@@ -903,7 +903,7 @@ void EditorNode::_set_scene_metadata(const String &p_file, int p_idx) {
 	}
 
 	Error err = cf->save(path);
-	ERR_FAIL_COND(err != OK);
+	ERR_FAIL_COND_MSG(err != OK, "Cannot save config file to '" + path + "'.");
 }
 
 bool EditorNode::_find_and_save_resource(RES p_res, Map<RES, bool> &processed, int32_t flags) {
@@ -2597,7 +2597,7 @@ void EditorNode::_save_screenshot(NodePath p_path) {
 	img->flip_y();
 	viewport->set_clear_mode(Viewport::CLEAR_MODE_ALWAYS);
 	Error error = img->save_png(p_path);
-	ERR_FAIL_COND(error != OK);
+	ERR_FAIL_COND_MSG(error != OK, "Cannot save screenshot to file '" + p_path + "'.");
 }
 
 void EditorNode::_tool_menu_option(int p_idx) {
@@ -3676,7 +3676,7 @@ Ref<Texture> EditorNode::get_object_icon(const Object *p_object, const String &p
 }
 
 Ref<Texture> EditorNode::get_class_icon(const String &p_class, const String &p_fallback) const {
-	ERR_FAIL_COND_V(p_class.empty(), NULL);
+	ERR_FAIL_COND_V_MSG(p_class.empty(), NULL, "Class name cannot be empty.");
 
 	if (gui_base->has_icon(p_class, "EditorIcons")) {
 		return gui_base->get_icon(p_class, "EditorIcons");
diff --git a/editor/editor_properties.cpp b/editor/editor_properties.cpp
index 30fb561fbe..7c74dc7d63 100644
--- a/editor/editor_properties.cpp
+++ b/editor/editor_properties.cpp
@@ -2038,7 +2038,7 @@ void EditorPropertyResource::_file_selected(const String &p_path) {
 
 	RES res = ResourceLoader::load(p_path);
 
-	ERR_FAIL_COND(res.is_null());
+	ERR_FAIL_COND_MSG(res.is_null(), "Cannot load resource from path '" + p_path + "'.");
 
 	List<PropertyInfo> prop_list;
 	get_edited_object()->get_property_list(&prop_list);
diff --git a/editor/editor_resource_preview.cpp b/editor/editor_resource_preview.cpp
index 5c15ebb1eb..b528cda8ff 100644
--- a/editor/editor_resource_preview.cpp
+++ b/editor/editor_resource_preview.cpp
@@ -203,7 +203,7 @@ void EditorResourcePreview::_generate_preview(Ref<ImageTexture> &r_texture, Ref<
 			}
 			Error err;
 			FileAccess *f = FileAccess::open(cache_base + ".txt", FileAccess::WRITE, &err);
-			ERR_FAIL_COND(err != OK);
+			ERR_FAIL_COND_MSG(err != OK, "Cannot create file '" + cache_base + ".txt'.");
 			f->store_line(itos(thumbnail_size));
 			f->store_line(itos(has_small_texture));
 			f->store_line(itos(FileAccess::get_modified_time(p_item.path)));
@@ -450,7 +450,7 @@ void EditorResourcePreview::check_for_invalidation(const String &p_path) {
 }
 
 void EditorResourcePreview::start() {
-	ERR_FAIL_COND(thread);
+	ERR_FAIL_COND_MSG(thread, "Thread already started.");
 	thread = Thread::create(_thread_func, this);
 }
 
diff --git a/editor/editor_settings.cpp b/editor/editor_settings.cpp
index 479fe5f0cb..9d24e443c4 100644
--- a/editor/editor_settings.cpp
+++ b/editor/editor_settings.cpp
@@ -793,13 +793,13 @@ void EditorSettings::create() {
 		self_contained = true;
 		Error err = extra_config->load(exe_path + "/._sc_");
 		if (err != OK) {
-			ERR_PRINTS("Can't load config from path: " + exe_path + "/._sc_");
+			ERR_PRINTS("Can't load config from path '" + exe_path + "/._sc_'.");
 		}
 	} else if (d->file_exists(exe_path + "/_sc_")) {
 		self_contained = true;
 		Error err = extra_config->load(exe_path + "/_sc_");
 		if (err != OK) {
-			ERR_PRINTS("Can't load config from path: " + exe_path + "/_sc_");
+			ERR_PRINTS("Can't load config from path '" + exe_path + "/_sc_'.");
 		}
 	}
 	memdelete(d);
@@ -1235,10 +1235,10 @@ void EditorSettings::set_project_metadata(const String &p_section, const String
 	String path = get_project_settings_dir().plus_file("project_metadata.cfg");
 	Error err;
 	err = cf->load(path);
-	ERR_FAIL_COND(err != OK && err != ERR_FILE_NOT_FOUND);
+	ERR_FAIL_COND_MSG(err != OK && err != ERR_FILE_NOT_FOUND, "Cannot load editor settings from file '" + path + "'.");
 	cf->set_value(p_section, p_key, p_data);
 	err = cf->save(path);
-	ERR_FAIL_COND(err != OK);
+	ERR_FAIL_COND_MSG(err != OK, "Cannot save editor settings to file '" + path + "'.");
 }
 
 Variant EditorSettings::get_project_metadata(const String &p_section, const String &p_key, Variant p_default) const {
diff --git a/editor/export_template_manager.cpp b/editor/export_template_manager.cpp
index 536cfaa1dd..324b74c6c8 100644
--- a/editor/export_template_manager.cpp
+++ b/editor/export_template_manager.cpp
@@ -321,7 +321,7 @@ bool ExportTemplateManager::_install_from_file(const String &p_file, bool p_use_
 		if (!f) {
 			ret = unzGoToNextFile(pkg);
 			fc++;
-			ERR_CONTINUE_MSG(true, "Can't open file from path: " + String(to_write) + ".");
+			ERR_CONTINUE_MSG(true, "Can't open file from path '" + String(to_write) + "'.");
 		}
 
 		f->store_buffer(data.ptr(), data.size());
diff --git a/editor/file_type_cache.cpp b/editor/file_type_cache.cpp
index 746d38f2b5..602906cb8d 100644
--- a/editor/file_type_cache.cpp
+++ b/editor/file_type_cache.cpp
@@ -99,6 +99,6 @@ void FileTypeCache::save() {
 
 FileTypeCache::FileTypeCache() {
 
-	ERR_FAIL_COND(singleton);
+	ERR_FAIL_COND_MSG(singleton, "FileTypeCache singleton already exist.");
 	singleton = this;
 }
diff --git a/editor/filesystem_dock.cpp b/editor/filesystem_dock.cpp
index a729befe8e..426ea8f196 100644
--- a/editor/filesystem_dock.cpp
+++ b/editor/filesystem_dock.cpp
@@ -1709,7 +1709,7 @@ void FileSystemDock::_file_option(int p_option, const Vector<String> &p_selected
 				reimport.push_back(p_selected[i]);
 			}
 
-			ERR_FAIL_COND(reimport.size() == 0);
+			ERR_FAIL_COND_MSG(reimport.size() == 0, "You need to select files to reimport them.");
 		} break;
 
 		case FILE_NEW_FOLDER: {
@@ -2087,7 +2087,7 @@ void FileSystemDock::_get_drag_target_folder(String &target, bool &target_favori
 
 void FileSystemDock::_file_and_folders_fill_popup(PopupMenu *p_popup, Vector<String> p_paths, bool p_display_path_dependent_options) {
 	// Add options for files and folders.
-	ERR_FAIL_COND(p_paths.empty());
+	ERR_FAIL_COND_MSG(p_paths.empty(), "Path cannot be empty.");
 
 	Vector<String> filenames;
 	Vector<String> foldernames;
diff --git a/editor/find_in_files.cpp b/editor/find_in_files.cpp
index def22d07de..752e49a932 100644
--- a/editor/find_in_files.cpp
+++ b/editor/find_in_files.cpp
@@ -829,7 +829,7 @@ void FindInFilesPanel::apply_replaces_in_file(String fpath, const Vector<Result>
 	// however that means either losing changes or losing replaces.
 
 	FileAccess *f = FileAccess::open(fpath, FileAccess::READ);
-	ERR_FAIL_COND(f == NULL);
+	ERR_FAIL_COND_MSG(f == NULL, "Cannot open file from path '" + fpath + "'.");
 
 	String buffer;
 	int current_line = 1;
@@ -876,7 +876,7 @@ void FindInFilesPanel::apply_replaces_in_file(String fpath, const Vector<Result>
 	// Now the modified contents are in the buffer, rewrite the file with our changes
 
 	Error err = f->reopen(fpath, FileAccess::WRITE);
-	ERR_FAIL_COND(err != OK);
+	ERR_FAIL_COND_MSG(err != OK, "Cannot create file in path '" + fpath + "'.");
 
 	f->store_string(buffer);
 
diff --git a/editor/import/editor_import_collada.cpp b/editor/import/editor_import_collada.cpp
index 449124acec..aa4408bc13 100644
--- a/editor/import/editor_import_collada.cpp
+++ b/editor/import/editor_import_collada.cpp
@@ -1208,7 +1208,7 @@ Error ColladaImport::_create_resources(Collada::Node *p_node, bool p_use_compres
 					const Collada::MeshData &meshdata = collada.state.mesh_data_map[meshid];
 					mesh->set_name(meshdata.name);
 					Error err = _create_mesh_surfaces(morphs.size() == 0, mesh, ng2->material_map, meshdata, apply_xform, bone_remap, skin, morph, morphs, p_use_compression, use_mesh_builtin_materials);
-					ERR_FAIL_COND_V(err, err);
+					ERR_FAIL_COND_V_MSG(err, err, "Cannot create mesh surface.");
 
 					mesh_cache[meshid] = mesh;
 				} else {
@@ -1260,7 +1260,7 @@ Error ColladaImport::_create_resources(Collada::Node *p_node, bool p_use_compres
 Error ColladaImport::load(const String &p_path, int p_flags, bool p_force_make_tangents, bool p_use_compression) {
 
 	Error err = collada.load(p_path, p_flags);
-	ERR_FAIL_COND_V(err, err);
+	ERR_FAIL_COND_V_MSG(err, err, "Cannot load file '" + p_path + "'.");
 
 	force_make_tangents = p_force_make_tangents;
 	ERR_FAIL_COND_V(!collada.state.visual_scene_map.has(collada.state.root_visual_scene), ERR_INVALID_DATA);
@@ -1778,7 +1778,7 @@ Node *EditorSceneImporterCollada::import_scene(const String &p_path, uint32_t p_
 
 	Error err = state.load(p_path, flags, p_flags & EditorSceneImporter::IMPORT_GENERATE_TANGENT_ARRAYS, p_flags & EditorSceneImporter::IMPORT_USE_COMPRESSION);
 
-	ERR_FAIL_COND_V(err != OK, NULL);
+	ERR_FAIL_COND_V_MSG(err != OK, NULL, "Cannot load scene from file '" + p_path + "'.");
 
 	if (state.missing_textures.size()) {
 
@@ -1831,7 +1831,7 @@ Ref<Animation> EditorSceneImporterCollada::import_animation(const String &p_path
 	state.use_mesh_builtin_materials = false;
 
 	Error err = state.load(p_path, Collada::IMPORT_FLAG_ANIMATION, p_flags & EditorSceneImporter::IMPORT_GENERATE_TANGENT_ARRAYS);
-	ERR_FAIL_COND_V(err != OK, RES());
+	ERR_FAIL_COND_V_MSG(err != OK, RES(), "Cannot load animation from file '" + p_path + "'.");
 
 	state.create_animations(p_flags & EditorSceneImporter::IMPORT_ANIMATION_FORCE_ALL_TRACKS_IN_ALL_CLIPS, p_flags & EditorSceneImporter::IMPORT_ANIMATION_KEEP_VALUE_TRACKS);
 	if (state.scene)
diff --git a/editor/import/editor_scene_importer_gltf.cpp b/editor/import/editor_scene_importer_gltf.cpp
index 9ea7c86e0c..c21ac42622 100644
--- a/editor/import/editor_scene_importer_gltf.cpp
+++ b/editor/import/editor_scene_importer_gltf.cpp
@@ -1670,14 +1670,14 @@ Error EditorSceneImporterGLTF::_parse_animations(GLTFState &state) {
 					track->weight_tracks.write[k] = cf;
 				}
 			} else {
-				WARN_PRINTS("Invalid path: " + path);
+				WARN_PRINTS("Invalid path '" + path + "'.");
 			}
 		}
 
 		state.animations.push_back(animation);
 	}
 
-	print_verbose("glTF: Total animations: " + itos(state.animations.size()));
+	print_verbose("glTF: Total animations '" + itos(state.animations.size()) + "'.");
 
 	return OK;
 }
diff --git a/editor/import/resource_importer_csv_translation.cpp b/editor/import/resource_importer_csv_translation.cpp
index 301422a25a..d988e1dcc3 100644
--- a/editor/import/resource_importer_csv_translation.cpp
+++ b/editor/import/resource_importer_csv_translation.cpp
@@ -90,7 +90,7 @@ Error ResourceImporterCSVTranslation::import(const String &p_source_file, const
 
 	FileAccessRef f = FileAccess::open(p_source_file, FileAccess::READ);
 
-	ERR_FAIL_COND_V(!f, ERR_INVALID_PARAMETER);
+	ERR_FAIL_COND_V_MSG(!f, ERR_INVALID_PARAMETER, "Cannot open file from path '" + p_source_file + "'.");
 
 	Vector<String> line = f->get_csv_line(delimiter);
 	ERR_FAIL_COND_V(line.size() <= 1, ERR_PARSE_ERROR);
diff --git a/editor/import/resource_importer_image.cpp b/editor/import/resource_importer_image.cpp
index ed8ea5497a..3d7663ba8f 100644
--- a/editor/import/resource_importer_image.cpp
+++ b/editor/import/resource_importer_image.cpp
@@ -78,7 +78,7 @@ Error ResourceImporterImage::import(const String &p_source_file, const String &p
 
 	FileAccess *f = FileAccess::open(p_source_file, FileAccess::READ);
 
-	ERR_FAIL_COND_V(!f, ERR_CANT_OPEN);
+	ERR_FAIL_COND_V_MSG(!f, ERR_CANT_OPEN, "Cannot open file from path '" + p_source_file + "'.");
 
 	size_t len = f->get_len();
 
@@ -90,6 +90,7 @@ Error ResourceImporterImage::import(const String &p_source_file, const String &p
 	memdelete(f);
 
 	f = FileAccess::open(p_save_path + ".image", FileAccess::WRITE);
+	ERR_FAIL_COND_V_MSG(!f, ERR_CANT_CREATE, "Cannot create file in path '" + p_save_path + ".image'.");
 
 	//save the header GDIM
 	const uint8_t header[4] = { 'G', 'D', 'I', 'M' };
diff --git a/editor/import/resource_importer_obj.cpp b/editor/import/resource_importer_obj.cpp
index 9061c92f6e..31a099ef83 100644
--- a/editor/import/resource_importer_obj.cpp
+++ b/editor/import/resource_importer_obj.cpp
@@ -509,7 +509,7 @@ Error ResourceImporterOBJ::import(const String &p_source_file, const String &p_s
 
 	err = ResourceSaver::save(save_path, meshes.front()->get());
 
-	ERR_FAIL_COND_V(err != OK, err);
+	ERR_FAIL_COND_V_MSG(err != OK, err, "Cannot save Mesh to file '" + save_path + "'.");
 
 	r_gen_files->push_back(save_path);
 
diff --git a/editor/import/resource_importer_scene.cpp b/editor/import/resource_importer_scene.cpp
index 64994e21b0..681e82de01 100644
--- a/editor/import/resource_importer_scene.cpp
+++ b/editor/import/resource_importer_scene.cpp
@@ -1418,7 +1418,7 @@ Error ResourceImporterScene::import(const String &p_source_file, const String &p
 			DirAccess *da = DirAccess::open(base_path);
 			Error err2 = da->make_dir(subdir_name);
 			memdelete(da);
-			ERR_FAIL_COND_V(err2 != OK && err2 != ERR_ALREADY_EXISTS, err2);
+			ERR_FAIL_COND_V_MSG(err2 != OK && err2 != ERR_ALREADY_EXISTS, err2, "Cannot make directory '" + subdir_name + "'.");
 			base_path = base_path.plus_file(subdir_name);
 		}
 	}
@@ -1514,7 +1514,7 @@ Error ResourceImporterScene::import(const String &p_source_file, const String &p
 			Ref<PackedScene> packer = memnew(PackedScene);
 			packer->pack(child);
 			err = ResourceSaver::save(path, packer); //do not take over, let the changed files reload themselves
-			ERR_FAIL_COND_V(err != OK, err);
+			ERR_FAIL_COND_V_MSG(err != OK, err, "Cannot save scene to file '" + path + "'.");
 		}
 	}
 
@@ -1522,7 +1522,7 @@ Error ResourceImporterScene::import(const String &p_source_file, const String &p
 	packer->pack(scene);
 	print_verbose("Saving scene to: " + p_save_path + ".scn");
 	err = ResourceSaver::save(p_save_path + ".scn", packer); //do not take over, let the changed files reload themselves
-	ERR_FAIL_COND_V(err != OK, err);
+	ERR_FAIL_COND_V_MSG(err != OK, err, "Cannot save scene to file '" + p_save_path + ".scn'.");
 
 	memdelete(scene);
 
@@ -1549,7 +1549,7 @@ Node *EditorSceneImporterESCN::import_scene(const String &p_path, uint32_t p_fla
 
 	Error error;
 	Ref<PackedScene> ps = ResourceFormatLoaderText::singleton->load(p_path, p_path, &error);
-	ERR_FAIL_COND_V(!ps.is_valid(), NULL);
+	ERR_FAIL_COND_V_MSG(!ps.is_valid(), NULL, "Cannot load scene as text resource from path '" + p_path + "'.");
 
 	Node *scene = ps->instance();
 	ERR_FAIL_COND_V(!scene, NULL);
diff --git a/editor/import/resource_importer_wav.cpp b/editor/import/resource_importer_wav.cpp
index f1de71e25e..74586a4100 100644
--- a/editor/import/resource_importer_wav.cpp
+++ b/editor/import/resource_importer_wav.cpp
@@ -96,7 +96,7 @@ Error ResourceImporterWAV::import(const String &p_source_file, const String &p_s
 	Error err;
 	FileAccess *file = FileAccess::open(p_source_file, FileAccess::READ, &err);
 
-	ERR_FAIL_COND_V(err != OK, ERR_CANT_OPEN);
+	ERR_FAIL_COND_V_MSG(err != OK, ERR_CANT_OPEN, "Cannot open file '" + p_source_file + "'.");
 
 	/* CHECK RIFF */
 	char riff[5];
diff --git a/editor/plugin_config_dialog.cpp b/editor/plugin_config_dialog.cpp
index 23056d25c0..971e746509 100644
--- a/editor/plugin_config_dialog.cpp
+++ b/editor/plugin_config_dialog.cpp
@@ -131,7 +131,7 @@ void PluginConfigDialog::config(const String &p_config_path) {
 	if (p_config_path.length()) {
 		Ref<ConfigFile> cf = memnew(ConfigFile);
 		Error err = cf->load(p_config_path);
-		ERR_FAIL_COND(err != OK);
+		ERR_FAIL_COND_MSG(err != OK, "Cannot load config file from path '" + p_config_path + "'.");
 
 		name_edit->set_text(cf->get_value("plugin", "name", ""));
 		subfolder_edit->set_text(p_config_path.get_base_dir().get_basename().get_file());
diff --git a/editor/plugins/animation_player_editor_plugin.cpp b/editor/plugins/animation_player_editor_plugin.cpp
index 173079b6de..8625b9857c 100644
--- a/editor/plugins/animation_player_editor_plugin.cpp
+++ b/editor/plugins/animation_player_editor_plugin.cpp
@@ -734,8 +734,8 @@ void AnimationPlayerEditor::_dialog_action(String p_file) {
 			ERR_FAIL_COND(!player);
 
 			Ref<Resource> res = ResourceLoader::load(p_file, "Animation");
-			ERR_FAIL_COND(res.is_null());
-			ERR_FAIL_COND(!res->is_class("Animation"));
+			ERR_FAIL_COND_MSG(res.is_null(), "Cannot load Animation from file '" + p_file + "'.");
+			ERR_FAIL_COND_MSG(!res->is_class("Animation"), "Loaded resource from file '" + p_file + "' is not Animation.");
 			if (p_file.find_last("/") != -1) {
 
 				p_file = p_file.substr(p_file.find_last("/") + 1, p_file.length());
diff --git a/editor/plugins/cpu_particles_2d_editor_plugin.cpp b/editor/plugins/cpu_particles_2d_editor_plugin.cpp
index 9d625af959..374900d4c7 100644
--- a/editor/plugins/cpu_particles_2d_editor_plugin.cpp
+++ b/editor/plugins/cpu_particles_2d_editor_plugin.cpp
@@ -87,7 +87,7 @@ void CPUParticles2DEditorPlugin::_generate_emission_mask() {
 	Ref<Image> img;
 	img.instance();
 	Error err = ImageLoader::load_image(source_emission_file, img);
-	ERR_FAIL_COND_MSG(err != OK, "Error loading image: " + source_emission_file + ".");
+	ERR_FAIL_COND_MSG(err != OK, "Error loading image '" + source_emission_file + "'.");
 
 	if (img->is_compressed()) {
 		img->decompress();
diff --git a/editor/plugins/curve_editor_plugin.cpp b/editor/plugins/curve_editor_plugin.cpp
index c2b6031e60..98db911799 100644
--- a/editor/plugins/curve_editor_plugin.cpp
+++ b/editor/plugins/curve_editor_plugin.cpp
@@ -779,7 +779,7 @@ bool CurvePreviewGenerator::handles(const String &p_type) const {
 Ref<Texture> CurvePreviewGenerator::generate(const Ref<Resource> &p_from, const Size2 &p_size) const {
 
 	Ref<Curve> curve_ref = p_from;
-	ERR_FAIL_COND_V(curve_ref.is_null(), Ref<Texture>());
+	ERR_FAIL_COND_V_MSG(curve_ref.is_null(), Ref<Texture>(), "It's not a reference to a valid Resource object.");
 	Curve &curve = **curve_ref;
 
 	// FIXME: Should be ported to use p_size as done in b2633a97
diff --git a/editor/plugins/mesh_library_editor_plugin.cpp b/editor/plugins/mesh_library_editor_plugin.cpp
index 1fc6dae978..7fbb35e565 100644
--- a/editor/plugins/mesh_library_editor_plugin.cpp
+++ b/editor/plugins/mesh_library_editor_plugin.cpp
@@ -201,7 +201,7 @@ void MeshLibraryEditor::_import_scene_cbk(const String &p_str) {
 	ERR_FAIL_COND(ps.is_null());
 	Node *scene = ps->instance();
 
-	ERR_FAIL_COND(!scene);
+	ERR_FAIL_COND_MSG(!scene, "Cannot create an instance from PackedScene '" + p_str + "'.");
 
 	_import_scene(scene, mesh_library, option == MENU_OPTION_UPDATE_FROM_SCENE);
 
diff --git a/editor/plugins/particles_2d_editor_plugin.cpp b/editor/plugins/particles_2d_editor_plugin.cpp
index 8025e12885..957ce42304 100644
--- a/editor/plugins/particles_2d_editor_plugin.cpp
+++ b/editor/plugins/particles_2d_editor_plugin.cpp
@@ -160,7 +160,7 @@ void Particles2DEditorPlugin::_generate_emission_mask() {
 	Ref<Image> img;
 	img.instance();
 	Error err = ImageLoader::load_image(source_emission_file, img);
-	ERR_FAIL_COND_MSG(err != OK, "Error loading image: " + source_emission_file + ".");
+	ERR_FAIL_COND_MSG(err != OK, "Error loading image '" + source_emission_file + "'.");
 
 	if (img->is_compressed()) {
 		img->decompress();
diff --git a/editor/plugins/script_editor_plugin.cpp b/editor/plugins/script_editor_plugin.cpp
index 8b6bab374c..e43528a79e 100644
--- a/editor/plugins/script_editor_plugin.cpp
+++ b/editor/plugins/script_editor_plugin.cpp
@@ -1965,7 +1965,7 @@ Ref<TextFile> ScriptEditor::_load_text_file(const String &p_path, Error *r_error
 	Ref<TextFile> text_res(text_file);
 	Error err = text_file->load_text(path);
 
-	ERR_FAIL_COND_V(err != OK, RES());
+	ERR_FAIL_COND_V_MSG(err != OK, RES(), "Cannot load text file '" + path + "'.");
 
 	text_file->set_file_path(local_path);
 	text_file->set_path(local_path, true);
@@ -1990,10 +1990,7 @@ Error ScriptEditor::_save_text_file(Ref<TextFile> p_text_file, const String &p_p
 	Error err;
 	FileAccess *file = FileAccess::open(p_path, FileAccess::WRITE, &err);
 
-	if (err) {
-
-		ERR_FAIL_COND_V(err, err);
-	}
+	ERR_FAIL_COND_V_MSG(err, err, "Cannot save text file '" + p_path + "'.");
 
 	file->store_string(source);
 	if (file->get_error() != OK && file->get_error() != ERR_FILE_EOF) {
diff --git a/editor/plugins/theme_editor_plugin.cpp b/editor/plugins/theme_editor_plugin.cpp
index 3055a9382c..d501a04016 100644
--- a/editor/plugins/theme_editor_plugin.cpp
+++ b/editor/plugins/theme_editor_plugin.cpp
@@ -192,7 +192,7 @@ void ThemeEditor::_save_template_cbk(String fname) {
 
 	FileAccess *file = FileAccess::open(filename, FileAccess::WRITE);
 
-	ERR_FAIL_COND_MSG(!file, "Can't save theme to file: " + filename + ".");
+	ERR_FAIL_COND_MSG(!file, "Can't save theme to file '" + filename + "'.");
 
 	file->store_line("; ******************* ");
 	file->store_line("; Template Theme File ");
diff --git a/editor/progress_dialog.cpp b/editor/progress_dialog.cpp
index 8dac5fa6b5..04b863f3aa 100644
--- a/editor/progress_dialog.cpp
+++ b/editor/progress_dialog.cpp
@@ -38,7 +38,7 @@
 void BackgroundProgress::_add_task(const String &p_task, const String &p_label, int p_steps) {
 
 	_THREAD_SAFE_METHOD_
-	ERR_FAIL_COND(tasks.has(p_task));
+	ERR_FAIL_COND_MSG(tasks.has(p_task), "Task '" + p_task + "' already exists.");
 	BackgroundProgress::Task t;
 	t.hb = memnew(HBoxContainer);
 	Label *l = memnew(Label);
@@ -172,7 +172,7 @@ void ProgressDialog::add_task(const String &p_task, const String &p_label, int p
 		return;
 	}
 
-	ERR_FAIL_COND(tasks.has(p_task));
+	ERR_FAIL_COND_MSG(tasks.has(p_task), "Task '" + p_task + "' already exists.");
 	ProgressDialog::Task t;
 	t.vb = memnew(VBoxContainer);
 	VBoxContainer *vb2 = memnew(VBoxContainer);
diff --git a/main/main.cpp b/main/main.cpp
index 9ae885a5ce..5de5c52b14 100644
--- a/main/main.cpp
+++ b/main/main.cpp
@@ -1182,7 +1182,7 @@ Error Main::setup2(Thread::ID p_main_tid_override) {
 			boot_logo.instance();
 			Error load_err = ImageLoader::load_image(boot_logo_path, boot_logo);
 			if (load_err)
-				ERR_PRINTS("Non-existing or invalid boot splash at: " + boot_logo_path + ". Loading default splash.");
+				ERR_PRINTS("Non-existing or invalid boot splash at '" + boot_logo_path + "'. Loading default splash.");
 		}
 
 		Color boot_bg_color = GLOBAL_DEF("application/boot_splash/bg_color", boot_splash_bg_color);
diff --git a/modules/csg/csg_shape.cpp b/modules/csg/csg_shape.cpp
index 23725c4960..45f8fdd2a8 100644
--- a/modules/csg/csg_shape.cpp
+++ b/modules/csg/csg_shape.cpp
@@ -282,7 +282,7 @@ void CSGShape::_update_shape() {
 	root_mesh.unref(); //byebye root mesh
 
 	CSGBrush *n = _get_brush();
-	ERR_FAIL_COND(!n);
+	ERR_FAIL_COND_MSG(!n, "Cannot get CSGBrush.");
 
 	OAHashMap<Vector3, Vector3> vec_map;
 
@@ -2407,7 +2407,7 @@ NodePath CSGPolygon::get_path_node() const {
 }
 
 void CSGPolygon::set_path_interval(float p_interval) {
-	ERR_FAIL_COND(p_interval < 0.001);
+	ERR_FAIL_COND_MSG(p_interval < 0.001, "Path interval cannot be smaller than 0.001.");
 	path_interval = p_interval;
 	_make_dirty();
 	update_gizmo();
diff --git a/modules/dds/texture_loader_dds.cpp b/modules/dds/texture_loader_dds.cpp
index 0220dcae4a..16a0f9d6ee 100644
--- a/modules/dds/texture_loader_dds.cpp
+++ b/modules/dds/texture_loader_dds.cpp
@@ -108,7 +108,7 @@ RES ResourceFormatDDS::load(const String &p_path, const String &p_original_path,
 	if (r_error)
 		*r_error = ERR_FILE_CORRUPT;
 
-	ERR_FAIL_COND_V_MSG(err != OK, RES(), "Unable to open DDS texture file: " + p_path + ".");
+	ERR_FAIL_COND_V_MSG(err != OK, RES(), "Unable to open DDS texture file '" + p_path + "'.");
 
 	uint32_t magic = f->get_32();
 	uint32_t hsize = f->get_32();
@@ -127,7 +127,7 @@ RES ResourceFormatDDS::load(const String &p_path, const String &p_original_path,
 
 	if (magic != DDS_MAGIC || hsize != 124 || !(flags & DDSD_PIXELFORMAT) || !(flags & DDSD_CAPS)) {
 
-		ERR_FAIL_V_MSG(RES(), "Invalid or unsupported DDS texture file: " + p_path + ".");
+		ERR_FAIL_V_MSG(RES(), "Invalid or unsupported DDS texture file '" + p_path + "'.");
 	}
 
 	/* uint32_t format_size = */ f->get_32();
@@ -216,7 +216,7 @@ RES ResourceFormatDDS::load(const String &p_path, const String &p_original_path,
 	} else {
 
 		printf("unrecognized fourcc %x format_flags: %x - rgbbits %i - red_mask %x green mask %x blue mask %x alpha mask %x\n", format_fourcc, format_flags, format_rgb_bits, format_red_mask, format_green_mask, format_blue_mask, format_alpha_mask);
-		ERR_FAIL_V_MSG(RES(), "Unrecognized or unsupported color layout in DDS: " + p_path + ".");
+		ERR_FAIL_V_MSG(RES(), "Unrecognized or unsupported color layout in DDS '" + p_path + "'.");
 	}
 
 	if (!(flags & DDSD_MIPMAPCOUNT))
diff --git a/modules/enet/networked_multiplayer_enet.cpp b/modules/enet/networked_multiplayer_enet.cpp
index 44f69ca261..a787cd3b80 100644
--- a/modules/enet/networked_multiplayer_enet.cpp
+++ b/modules/enet/networked_multiplayer_enet.cpp
@@ -543,7 +543,7 @@ Error NetworkedMultiplayerENet::put_packet(const uint8_t *p_buffer, int p_buffer
 	if (target_peer != 0) {
 
 		E = peer_map.find(ABS(target_peer));
-		ERR_FAIL_COND_V_MSG(!E, ERR_INVALID_PARAMETER, "Invalid target peer: " + itos(target_peer) + ".");
+		ERR_FAIL_COND_V_MSG(!E, ERR_INVALID_PARAMETER, "Invalid target peer '" + itos(target_peer) + "'.");
 	}
 
 	ENetPacket *packet = enet_packet_create(NULL, p_buffer_size + 8, packet_flags);
diff --git a/modules/etc/texture_loader_pkm.cpp b/modules/etc/texture_loader_pkm.cpp
index dd61d816d4..4d8af6883f 100644
--- a/modules/etc/texture_loader_pkm.cpp
+++ b/modules/etc/texture_loader_pkm.cpp
@@ -56,14 +56,14 @@ RES ResourceFormatPKM::load(const String &p_path, const String &p_original_path,
 	if (r_error)
 		*r_error = ERR_FILE_CORRUPT;
 
-	ERR_FAIL_COND_V_MSG(err != OK, RES(), "Unable to open PKM texture file: " + p_path + ".");
+	ERR_FAIL_COND_V_MSG(err != OK, RES(), "Unable to open PKM texture file '" + p_path + "'.");
 
 	// big endian
 	f->set_endian_swap(true);
 
 	ETC1Header h;
 	f->get_buffer((uint8_t *)&h.tag, sizeof(h.tag));
-	ERR_FAIL_COND_V_MSG(strncmp(h.tag, "PKM 10", sizeof(h.tag)), RES(), "Invalid or unsupported PKM texture file: " + p_path + ".");
+	ERR_FAIL_COND_V_MSG(strncmp(h.tag, "PKM 10", sizeof(h.tag)), RES(), "Invalid or unsupported PKM texture file '" + p_path + "'.");
 
 	h.format = f->get_16();
 	h.texWidth = f->get_16();
diff --git a/modules/gdnative/pluginscript/pluginscript_script.cpp b/modules/gdnative/pluginscript/pluginscript_script.cpp
index 94d38e1be1..f7c961d38b 100644
--- a/modules/gdnative/pluginscript/pluginscript_script.cpp
+++ b/modules/gdnative/pluginscript/pluginscript_script.cpp
@@ -401,9 +401,7 @@ Error PluginScript::load_source_code(const String &p_path) {
 	PoolVector<uint8_t> sourcef;
 	Error err;
 	FileAccess *f = FileAccess::open(p_path, FileAccess::READ, &err);
-	if (err) {
-		ERR_FAIL_COND_V(err, err);
-	}
+	ERR_FAIL_COND_V_MSG(err, err, "Cannot open file '" + p_path + "'.");
 
 	int len = f->get_len();
 	sourcef.resize(len + 1);
diff --git a/modules/gdscript/gdscript.cpp b/modules/gdscript/gdscript.cpp
index 5dab063061..ea2296692c 100644
--- a/modules/gdscript/gdscript.cpp
+++ b/modules/gdscript/gdscript.cpp
@@ -2177,11 +2177,11 @@ RES ResourceFormatLoaderGDScript::load(const String &p_path, const String &p_ori
 		script->set_script_path(p_original_path); // script needs this.
 		script->set_path(p_original_path);
 		Error err = script->load_byte_code(p_path);
-		ERR_FAIL_COND_V(err != OK, RES());
+		ERR_FAIL_COND_V_MSG(err != OK, RES(), "Cannot load byte code from file '" + p_path + "'.");
 
 	} else {
 		Error err = script->load_source_code(p_path);
-		ERR_FAIL_COND_V(err != OK, RES());
+		ERR_FAIL_COND_V_MSG(err != OK, RES(), "Cannot load source code from file '" + p_path + "'.");
 
 		script->set_script_path(p_original_path); // script needs this.
 		script->set_path(p_original_path);
@@ -2217,7 +2217,7 @@ String ResourceFormatLoaderGDScript::get_resource_type(const String &p_path) con
 void ResourceFormatLoaderGDScript::get_dependencies(const String &p_path, List<String> *p_dependencies, bool p_add_types) {
 
 	FileAccessRef file = FileAccess::open(p_path, FileAccess::READ);
-	ERR_FAIL_COND(!file);
+	ERR_FAIL_COND_MSG(!file, "Cannot open file '" + p_path + "'.");
 
 	String source = file->get_as_utf8_string();
 	if (source.empty()) {
@@ -2244,10 +2244,7 @@ Error ResourceFormatSaverGDScript::save(const String &p_path, const RES &p_resou
 	Error err;
 	FileAccess *file = FileAccess::open(p_path, FileAccess::WRITE, &err);
 
-	if (err) {
-
-		ERR_FAIL_COND_V(err, err);
-	}
+	ERR_FAIL_COND_V_MSG(err, err, "Cannot save GDScript file '" + p_path + "'.");
 
 	file->store_string(source);
 	if (file->get_error() != OK && file->get_error() != ERR_FILE_EOF) {
diff --git a/modules/gdscript/gdscript_tokenizer.cpp b/modules/gdscript/gdscript_tokenizer.cpp
index 64b354bdb8..8b20b0ff48 100644
--- a/modules/gdscript/gdscript_tokenizer.cpp
+++ b/modules/gdscript/gdscript_tokenizer.cpp
@@ -1425,7 +1425,7 @@ Vector<uint8_t> GDScriptTokenizerBuffer::parse_code_string(const String &p_code)
 		int len;
 		// Objects cannot be constant, never encode objects
 		Error err = encode_variant(E->get(), NULL, len, false);
-		ERR_FAIL_COND_V(err != OK, Vector<uint8_t>());
+		ERR_FAIL_COND_V_MSG(err != OK, Vector<uint8_t>(), "Error when trying to encode Variant.");
 		int pos = buf.size();
 		buf.resize(pos + len);
 		encode_variant(E->get(), &buf.write[pos], len, false);
diff --git a/modules/mbedtls/crypto_mbedtls.cpp b/modules/mbedtls/crypto_mbedtls.cpp
index 1e02084ae2..ca656b4b9b 100644
--- a/modules/mbedtls/crypto_mbedtls.cpp
+++ b/modules/mbedtls/crypto_mbedtls.cpp
@@ -55,7 +55,7 @@ Error CryptoKeyMbedTLS::load(String p_path) {
 
 	PoolByteArray out;
 	FileAccess *f = FileAccess::open(p_path, FileAccess::READ);
-	ERR_FAIL_COND_V(!f, ERR_INVALID_PARAMETER);
+	ERR_FAIL_COND_V_MSG(!f, ERR_INVALID_PARAMETER, "Cannot open CryptoKeyMbedTLS file '" + p_path + "'.");
 
 	int flen = f->get_len();
 	out.resize(flen + 1);
@@ -69,14 +69,14 @@ Error CryptoKeyMbedTLS::load(String p_path) {
 	int ret = mbedtls_pk_parse_key(&pkey, out.read().ptr(), out.size(), NULL, 0);
 	// We MUST zeroize the memory for safety!
 	mbedtls_platform_zeroize(out.write().ptr(), out.size());
-	ERR_FAIL_COND_V_MSG(ret, FAILED, "Error parsing private key: " + itos(ret));
+	ERR_FAIL_COND_V_MSG(ret, FAILED, "Error parsing private key '" + itos(ret) + "'.");
 
 	return OK;
 }
 
 Error CryptoKeyMbedTLS::save(String p_path) {
 	FileAccess *f = FileAccess::open(p_path, FileAccess::WRITE);
-	ERR_FAIL_COND_V(!f, ERR_INVALID_PARAMETER);
+	ERR_FAIL_COND_V_MSG(!f, ERR_INVALID_PARAMETER, "Cannot save CryptoKeyMbedTLS file '" + p_path + "'.");
 
 	unsigned char w[16000];
 	memset(w, 0, sizeof(w));
@@ -85,7 +85,7 @@ Error CryptoKeyMbedTLS::save(String p_path) {
 	if (ret != 0) {
 		memdelete(f);
 		memset(w, 0, sizeof(w)); // Zeroize anything we might have written.
-		ERR_FAIL_V_MSG(FAILED, "Error writing key: " + itos(ret));
+		ERR_FAIL_V_MSG(FAILED, "Error writing key '" + itos(ret) + "'.");
 	}
 
 	size_t len = strlen((char *)w);
@@ -104,7 +104,7 @@ Error X509CertificateMbedTLS::load(String p_path) {
 
 	PoolByteArray out;
 	FileAccess *f = FileAccess::open(p_path, FileAccess::READ);
-	ERR_FAIL_COND_V(!f, ERR_INVALID_PARAMETER);
+	ERR_FAIL_COND_V_MSG(!f, ERR_INVALID_PARAMETER, "Cannot open X509CertificateMbedTLS file '" + p_path + "'.");
 
 	int flen = f->get_len();
 	out.resize(flen + 1);
@@ -131,7 +131,7 @@ Error X509CertificateMbedTLS::load_from_memory(const uint8_t *p_buffer, int p_le
 
 Error X509CertificateMbedTLS::save(String p_path) {
 	FileAccess *f = FileAccess::open(p_path, FileAccess::WRITE);
-	ERR_FAIL_COND_V(!f, ERR_INVALID_PARAMETER);
+	ERR_FAIL_COND_V_MSG(!f, ERR_INVALID_PARAMETER, "Cannot save X509CertificateMbedTLS file '" + p_path + "'.");
 
 	mbedtls_x509_crt *crt = &cert;
 	while (crt) {
@@ -140,7 +140,7 @@ Error X509CertificateMbedTLS::save(String p_path) {
 		int ret = mbedtls_pem_write_buffer(PEM_BEGIN_CRT, PEM_END_CRT, cert.raw.p, cert.raw.len, w, sizeof(w), &wrote);
 		if (ret != 0 || wrote == 0) {
 			memdelete(f);
-			ERR_FAIL_V_MSG(FAILED, "Error writing certificate: " + itos(ret));
+			ERR_FAIL_V_MSG(FAILED, "Error writing certificate '" + itos(ret) + "'.");
 		}
 
 		f->store_buffer(w, wrote - 1); // don't write the string terminator
diff --git a/modules/mono/class_db_api_json.cpp b/modules/mono/class_db_api_json.cpp
index 7580911a0a..bbc779601e 100644
--- a/modules/mono/class_db_api_json.cpp
+++ b/modules/mono/class_db_api_json.cpp
@@ -236,7 +236,7 @@ void class_db_api_to_json(const String &p_output_file, ClassDB::APIType p_api) {
 	}
 
 	FileAccessRef f = FileAccess::open(p_output_file, FileAccess::WRITE);
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "Cannot open file '" + p_output_file + "'.");
 	f->store_string(JSON::print(classes_dict, /*indent: */ "\t"));
 	f->close();
 
diff --git a/modules/mono/csharp_script.cpp b/modules/mono/csharp_script.cpp
index e14e919f92..83be10dee3 100644
--- a/modules/mono/csharp_script.cpp
+++ b/modules/mono/csharp_script.cpp
@@ -1195,7 +1195,7 @@ void CSharpLanguage::release_script_gchandle(MonoObject *p_expected_obj, Ref<Mon
 
 CSharpLanguage::CSharpLanguage() {
 
-	ERR_FAIL_COND(singleton);
+	ERR_FAIL_COND_MSG(singleton, "C# singleton already exist.");
 	singleton = this;
 
 	finalizing = false;
@@ -3242,7 +3242,7 @@ RES ResourceFormatLoaderCSharpScript::load(const String &p_path, const String &p
 
 #if defined(DEBUG_ENABLED) || defined(TOOLS_ENABLED)
 	Error err = script->load_source_code(p_path);
-	ERR_FAIL_COND_V(err != OK, RES());
+	ERR_FAIL_COND_V_MSG(err != OK, RES(), "Cannot load C# script file '" + p_path + "'.");
 #endif
 
 	script->set_path(p_original_path);
@@ -3325,7 +3325,7 @@ Error ResourceFormatSaverCSharpScript::save(const String &p_path, const RES &p_r
 
 	Error err;
 	FileAccess *file = FileAccess::open(p_path, FileAccess::WRITE, &err);
-	ERR_FAIL_COND_V(err, err);
+	ERR_FAIL_COND_V_MSG(err != OK, err, "Cannot save C# script file '" + p_path + "'.");
 
 	file->store_string(source);
 
diff --git a/modules/mono/editor/bindings_generator.cpp b/modules/mono/editor/bindings_generator.cpp
index 1888bb3cb9..e98db02d66 100644
--- a/modules/mono/editor/bindings_generator.cpp
+++ b/modules/mono/editor/bindings_generator.cpp
@@ -868,7 +868,7 @@ Error BindingsGenerator::generate_cs_core_project(const String &p_proj_dir, Vect
 
 	if (!DirAccess::exists(p_proj_dir)) {
 		Error err = da->make_dir_recursive(p_proj_dir);
-		ERR_FAIL_COND_V(err != OK, ERR_CANT_CREATE);
+		ERR_FAIL_COND_V_MSG(err != OK, ERR_CANT_CREATE, "Cannot create directory '" + p_proj_dir + "'.");
 	}
 
 	da->change_dir(p_proj_dir);
diff --git a/modules/mono/mono_gd/gd_mono_log.cpp b/modules/mono/mono_gd/gd_mono_log.cpp
index 5a0d728953..52f9eac638 100644
--- a/modules/mono/mono_gd/gd_mono_log.cpp
+++ b/modules/mono/mono_gd/gd_mono_log.cpp
@@ -104,7 +104,7 @@ void GDMonoLog::_delete_old_log_files(const String &p_logs_dir) {
 	ERR_FAIL_COND(!da);
 
 	Error err = da->change_dir(p_logs_dir);
-	ERR_FAIL_COND(err != OK);
+	ERR_FAIL_COND_MSG(err != OK, "Cannot change directory to '" + p_logs_dir + "'.");
 
 	ERR_FAIL_COND(da->list_dir_begin() != OK);
 
diff --git a/modules/mono/utils/string_utils.cpp b/modules/mono/utils/string_utils.cpp
index ae5a2cde81..3557e8de3a 100644
--- a/modules/mono/utils/string_utils.cpp
+++ b/modules/mono/utils/string_utils.cpp
@@ -165,7 +165,7 @@ Error read_all_file_utf8(const String &p_path, String &r_content) {
 	PoolVector<uint8_t> sourcef;
 	Error err;
 	FileAccess *f = FileAccess::open(p_path, FileAccess::READ, &err);
-	ERR_FAIL_COND_V(err != OK, err);
+	ERR_FAIL_COND_V_MSG(err != OK, err, "Cannot open file '" + p_path + "'.");
 
 	int len = f->get_len();
 	sourcef.resize(len + 1);
diff --git a/modules/opus/audio_stream_opus.cpp b/modules/opus/audio_stream_opus.cpp
index d3e8d3c9bb..43b0aecbf1 100644
--- a/modules/opus/audio_stream_opus.cpp
+++ b/modules/opus/audio_stream_opus.cpp
@@ -119,9 +119,7 @@ Error AudioStreamPlaybackOpus::_load_stream() {
 	Error err;
 	f = FileAccess::open(file, FileAccess::READ, &err);
 
-	if (err) {
-		ERR_FAIL_COND_V(err, err);
-	}
+	ERR_FAIL_COND_V_MSG(err, err, "Cannot open file '" + file + "'.");
 
 	int _err = 0;
 
@@ -185,9 +183,7 @@ Error AudioStreamPlaybackOpus::set_file(const String &p_file) {
 	Error err;
 	f = FileAccess::open(file, FileAccess::READ, &err);
 
-	if (err) {
-		ERR_FAIL_COND_V(err, err);
-	}
+	ERR_FAIL_COND_V_MSG(err, err, "Cannot open file '" + file + "'.");
 
 	int _err;
 
diff --git a/modules/stb_vorbis/resource_importer_ogg_vorbis.cpp b/modules/stb_vorbis/resource_importer_ogg_vorbis.cpp
index e10f29e310..977ff064bc 100644
--- a/modules/stb_vorbis/resource_importer_ogg_vorbis.cpp
+++ b/modules/stb_vorbis/resource_importer_ogg_vorbis.cpp
@@ -83,7 +83,7 @@ Error ResourceImporterOGGVorbis::import(const String &p_source_file, const Strin
 
 	FileAccess *f = FileAccess::open(p_source_file, FileAccess::READ);
 
-	ERR_FAIL_COND_V(!f, ERR_CANT_OPEN);
+	ERR_FAIL_COND_V_MSG(!f, ERR_CANT_OPEN, "Cannot open file '" + p_source_file + "'.");
 
 	size_t len = f->get_len();
 
diff --git a/modules/theora/video_stream_theora.cpp b/modules/theora/video_stream_theora.cpp
index 6a1b463305..28a8b77283 100644
--- a/modules/theora/video_stream_theora.cpp
+++ b/modules/theora/video_stream_theora.cpp
@@ -175,7 +175,7 @@ void VideoStreamPlaybackTheora::set_file(const String &p_file) {
 		memdelete(file);
 	}
 	file = FileAccess::open(p_file, FileAccess::READ);
-	ERR_FAIL_COND(!file);
+	ERR_FAIL_COND_MSG(!file, "Cannot open file '" + p_file + "'.");
 
 #ifdef THEORA_USE_THREAD_STREAMING
 	thread_exit = false;
diff --git a/modules/vorbis/audio_stream_ogg_vorbis.cpp b/modules/vorbis/audio_stream_ogg_vorbis.cpp
index 2f56e778b9..c330af60a4 100644
--- a/modules/vorbis/audio_stream_ogg_vorbis.cpp
+++ b/modules/vorbis/audio_stream_ogg_vorbis.cpp
@@ -242,10 +242,7 @@ Error AudioStreamPlaybackOGGVorbis::set_file(const String &p_file) {
 	stream_valid = false;
 	Error err;
 	f = FileAccess::open(file, FileAccess::READ, &err);
-
-	if (err) {
-		ERR_FAIL_COND_V(err, err);
-	}
+	ERR_FAIL_COND_V_MSG(err, err, "Cannot open file '" + p_file + "'.");
 
 	int errv = ov_open_callbacks(f, &vf, NULL, 0, _ov_callbacks);
 	switch (errv) {
@@ -294,9 +291,7 @@ Error AudioStreamPlaybackOGGVorbis::_load_stream() {
 
 	Error err;
 	f = FileAccess::open(file, FileAccess::READ, &err);
-	if (err) {
-		ERR_FAIL_COND_V(err, err);
-	}
+	ERR_FAIL_COND_V_MSG(err != OK, err, "Cannot open file '" + file + "'.");
 
 	int errv = ov_open_callbacks(f, &vf, NULL, 0, _ov_callbacks);
 	switch (errv) {
diff --git a/platform/android/export/export.cpp b/platform/android/export/export.cpp
index 441fa38bff..e019e5bd2f 100644
--- a/platform/android/export/export.cpp
+++ b/platform/android/export/export.cpp
@@ -598,7 +598,7 @@ class EditorExportPlatformAndroid : public EditorExportPlatform {
 				String dst_path = String("lib").plus_file(abi).plus_file(p_so.path.get_file());
 				Vector<uint8_t> array = FileAccess::get_file_as_array(p_so.path);
 				Error store_err = store_in_apk(ed, dst_path, array);
-				ERR_FAIL_COND_V(store_err, store_err);
+				ERR_FAIL_COND_V_MSG(store_err, store_err, "Cannot store in apk file '" + dst_path + "'.");
 			}
 		}
 		if (!exported) {
@@ -1666,7 +1666,7 @@ public:
 
 		DirAccessRef da = DirAccess::open("res://android");
 
-		ERR_FAIL_COND(!da);
+		ERR_FAIL_COND_MSG(!da, "Cannot open directory 'res://android'.");
 		Map<String, List<String> > directory_paths;
 		Map<String, List<String> > manifest_sections;
 		Map<String, List<String> > gradle_sections;
@@ -1942,7 +1942,7 @@ public:
 			//build project if custom build is enabled
 			String sdk_path = EDITOR_GET("export/android/custom_build_sdk_path");
 
-			ERR_FAIL_COND_V(sdk_path == "", ERR_UNCONFIGURED);
+			ERR_FAIL_COND_V_MSG(sdk_path == "", ERR_UNCONFIGURED, "Android SDK path must be configured in Editor Settings at 'export/android/custom_build_sdk_path'.");
 
 			_update_custom_build_project();
 
diff --git a/platform/android/file_access_jandroid.cpp b/platform/android/file_access_jandroid.cpp
index 5b8cf01138..d4c2a23aa0 100644
--- a/platform/android/file_access_jandroid.cpp
+++ b/platform/android/file_access_jandroid.cpp
@@ -94,13 +94,13 @@ void FileAccessJAndroid::seek(size_t p_position) {
 
 	JNIEnv *env = ThreadAndroid::get_env();
 
-	ERR_FAIL_COND(!is_open());
+	ERR_FAIL_COND_MSG(!is_open(), "File must be opened before use.");
 	env->CallVoidMethod(io, _file_seek, id, p_position);
 }
 
 void FileAccessJAndroid::seek_end(int64_t p_position) {
 
-	ERR_FAIL_COND(!is_open());
+	ERR_FAIL_COND_MSG(!is_open(), "File must be opened before use.");
 
 	seek(get_len());
 }
@@ -108,34 +108,34 @@ void FileAccessJAndroid::seek_end(int64_t p_position) {
 size_t FileAccessJAndroid::get_position() const {
 
 	JNIEnv *env = ThreadAndroid::get_env();
-	ERR_FAIL_COND_V(!is_open(), 0);
+	ERR_FAIL_COND_V_MSG(!is_open(), 0, "File must be opened before use.");
 	return env->CallIntMethod(io, _file_tell, id);
 }
 
 size_t FileAccessJAndroid::get_len() const {
 
 	JNIEnv *env = ThreadAndroid::get_env();
-	ERR_FAIL_COND_V(!is_open(), 0);
+	ERR_FAIL_COND_V_MSG(!is_open(), 0, "File must be opened before use.");
 	return env->CallIntMethod(io, _file_get_size, id);
 }
 
 bool FileAccessJAndroid::eof_reached() const {
 
 	JNIEnv *env = ThreadAndroid::get_env();
-	ERR_FAIL_COND_V(!is_open(), 0);
+	ERR_FAIL_COND_V_MSG(!is_open(), 0, "File must be opened before use.");
 	return env->CallIntMethod(io, _file_eof, id);
 }
 
 uint8_t FileAccessJAndroid::get_8() const {
 
-	ERR_FAIL_COND_V(!is_open(), 0);
+	ERR_FAIL_COND_V_MSG(!is_open(), 0, "File must be opened before use.");
 	uint8_t byte;
 	get_buffer(&byte, 1);
 	return byte;
 }
 int FileAccessJAndroid::get_buffer(uint8_t *p_dst, int p_length) const {
 
-	ERR_FAIL_COND_V(!is_open(), 0);
+	ERR_FAIL_COND_V_MSG(!is_open(), 0, "File must be opened before use.");
 	if (p_length == 0)
 		return 0;
 	JNIEnv *env = ThreadAndroid::get_env();
diff --git a/platform/iphone/export/export.cpp b/platform/iphone/export/export.cpp
index 1cbf4d6a70..1b2b343530 100644
--- a/platform/iphone/export/export.cpp
+++ b/platform/iphone/export/export.cpp
@@ -487,7 +487,7 @@ Error EditorExportPlatformIOS::_export_icons(const Ref<EditorExportPreset> &p_pr
 	String sizes;
 
 	DirAccess *da = DirAccess::open(p_iconset_dir);
-	ERR_FAIL_COND_V(!da, ERR_CANT_OPEN);
+	ERR_FAIL_COND_V_MSG(!da, ERR_CANT_OPEN, "Cannot open directory '" + p_iconset_dir + "'.");
 
 	for (unsigned int i = 0; i < (sizeof(icon_infos) / sizeof(icon_infos[0])); ++i) {
 		IconInfo info = icon_infos[i];
@@ -537,7 +537,7 @@ Error EditorExportPlatformIOS::_export_icons(const Ref<EditorExportPreset> &p_pr
 
 Error EditorExportPlatformIOS::_export_loading_screens(const Ref<EditorExportPreset> &p_preset, const String &p_dest_dir) {
 	DirAccess *da = DirAccess::open(p_dest_dir);
-	ERR_FAIL_COND_V(!da, ERR_CANT_OPEN);
+	ERR_FAIL_COND_V_MSG(!da, ERR_CANT_OPEN, "Cannot open directory '" + p_dest_dir + "'.");
 
 	for (unsigned int i = 0; i < sizeof(loading_screen_infos) / sizeof(loading_screen_infos[0]); ++i) {
 		LoadingScreenInfo info = loading_screen_infos[i];
@@ -546,7 +546,7 @@ Error EditorExportPlatformIOS::_export_loading_screens(const Ref<EditorExportPre
 			Error err = da->copy(loading_screen_file, p_dest_dir + info.export_name);
 			if (err) {
 				memdelete(da);
-				String err_str = String("Failed to export loading screen (") + info.preset_key + ") from path: " + loading_screen_file;
+				String err_str = String("Failed to export loading screen (") + info.preset_key + ") from path '" + loading_screen_file + "'.";
 				ERR_PRINT(err_str.utf8().get_data());
 				return err;
 			}
@@ -757,7 +757,7 @@ void EditorExportPlatformIOS::_add_assets_to_project(const Ref<EditorExportPrese
 
 Error EditorExportPlatformIOS::_export_additional_assets(const String &p_out_dir, const Vector<String> &p_assets, bool p_is_framework, Vector<IOSExportAsset> &r_exported_assets) {
 	DirAccess *filesystem_da = DirAccess::create(DirAccess::ACCESS_FILESYSTEM);
-	ERR_FAIL_COND_V(!filesystem_da, ERR_CANT_CREATE);
+	ERR_FAIL_COND_V_MSG(!filesystem_da, ERR_CANT_CREATE, "Cannot create DirAccess for path '" + p_out_dir + "'.");
 	for (int f_idx = 0; f_idx < p_assets.size(); ++f_idx) {
 		String asset = p_assets[f_idx];
 		if (!asset.begins_with("res://")) {
diff --git a/platform/javascript/api/api.cpp b/platform/javascript/api/api.cpp
index d4dc43d57c..0832ae0360 100644
--- a/platform/javascript/api/api.cpp
+++ b/platform/javascript/api/api.cpp
@@ -55,7 +55,7 @@ JavaScript *JavaScript::get_singleton() {
 
 JavaScript::JavaScript() {
 
-	ERR_FAIL_COND(singleton != NULL);
+	ERR_FAIL_COND_MSG(singleton != NULL, "JavaScript singleton already exist.");
 	singleton = this;
 }
 
diff --git a/platform/uwp/export/export.cpp b/platform/uwp/export/export.cpp
index ea110b11ca..d83061df89 100644
--- a/platform/uwp/export/export.cpp
+++ b/platform/uwp/export/export.cpp
@@ -1249,7 +1249,7 @@ public:
 		Error err = OK;
 
 		FileAccess *fa_pack = FileAccess::open(p_path, FileAccess::WRITE, &err);
-		ERR_FAIL_COND_V(err != OK, ERR_CANT_CREATE);
+		ERR_FAIL_COND_V_MSG(err != OK, ERR_CANT_CREATE, "Cannot create file '" + p_path + "'.");
 
 		AppxPackager packager;
 		packager.init(fa_pack);
diff --git a/platform/windows/os_windows.cpp b/platform/windows/os_windows.cpp
index be325381bb..facf5b8d91 100644
--- a/platform/windows/os_windows.cpp
+++ b/platform/windows/os_windows.cpp
@@ -2663,7 +2663,7 @@ String OS_Windows::get_executable_path() const {
 void OS_Windows::set_native_icon(const String &p_filename) {
 
 	FileAccess *f = FileAccess::open(p_filename, FileAccess::READ);
-	ERR_FAIL_COND(!f);
+	ERR_FAIL_COND_MSG(!f, "Cannot open file with icon '" + p_filename + "'.");
 
 	ICONDIR *icon_dir = (ICONDIR *)memalloc(sizeof(ICONDIR));
 	int pos = 0;
diff --git a/scene/2d/animated_sprite.cpp b/scene/2d/animated_sprite.cpp
index 0b20b781f0..20ec06f033 100644
--- a/scene/2d/animated_sprite.cpp
+++ b/scene/2d/animated_sprite.cpp
@@ -102,7 +102,7 @@ Rect2 AnimatedSprite::_get_rect() const {
 void SpriteFrames::add_frame(const StringName &p_anim, const Ref<Texture> &p_frame, int p_at_pos) {
 
 	Map<StringName, Anim>::Element *E = animations.find(p_anim);
-	ERR_FAIL_COND(!E);
+	ERR_FAIL_COND_MSG(!E, "Animation '" + String(p_anim) + "' doesn't exist.");
 
 	if (p_at_pos >= 0 && p_at_pos < E->get().frames.size())
 		E->get().frames.insert(p_at_pos, p_frame);
@@ -114,7 +114,7 @@ void SpriteFrames::add_frame(const StringName &p_anim, const Ref<Texture> &p_fra
 
 int SpriteFrames::get_frame_count(const StringName &p_anim) const {
 	const Map<StringName, Anim>::Element *E = animations.find(p_anim);
-	ERR_FAIL_COND_V(!E, 0);
+	ERR_FAIL_COND_V_MSG(!E, 0, "Animation '" + String(p_anim) + "' doesn't exist.");
 
 	return E->get().frames.size();
 }
@@ -122,7 +122,7 @@ int SpriteFrames::get_frame_count(const StringName &p_anim) const {
 void SpriteFrames::remove_frame(const StringName &p_anim, int p_idx) {
 
 	Map<StringName, Anim>::Element *E = animations.find(p_anim);
-	ERR_FAIL_COND(!E);
+	ERR_FAIL_COND_MSG(!E, "Animation '" + String(p_anim) + "' doesn't exist.");
 
 	E->get().frames.remove(p_idx);
 	emit_changed();
@@ -130,7 +130,7 @@ void SpriteFrames::remove_frame(const StringName &p_anim, int p_idx) {
 void SpriteFrames::clear(const StringName &p_anim) {
 
 	Map<StringName, Anim>::Element *E = animations.find(p_anim);
-	ERR_FAIL_COND(!E);
+	ERR_FAIL_COND_MSG(!E, "Animation '" + String(p_anim) + "' doesn't exist.");
 
 	E->get().frames.clear();
 	emit_changed();
@@ -144,7 +144,7 @@ void SpriteFrames::clear_all() {
 
 void SpriteFrames::add_animation(const StringName &p_anim) {
 
-	ERR_FAIL_COND(animations.has(p_anim));
+	ERR_FAIL_COND_MSG(animations.has(p_anim), "SpriteFrames already has animation '" + p_anim + "'.");
 
 	animations[p_anim] = Anim();
 	animations[p_anim].normal_name = String(p_anim) + NORMAL_SUFFIX;
@@ -161,8 +161,8 @@ void SpriteFrames::remove_animation(const StringName &p_anim) {
 
 void SpriteFrames::rename_animation(const StringName &p_prev, const StringName &p_next) {
 
-	ERR_FAIL_COND(!animations.has(p_prev));
-	ERR_FAIL_COND(animations.has(p_next));
+	ERR_FAIL_COND_MSG(!animations.has(p_prev), "SpriteFrames doesn't have animation '" + String(p_prev) + "'.");
+	ERR_FAIL_COND_MSG(animations.has(p_next), "Animation '" + String(p_next) + "' already exists.");
 
 	Anim anim = animations[p_prev];
 	animations.erase(p_prev);
@@ -202,26 +202,26 @@ Vector<String> SpriteFrames::get_animation_names() const {
 
 void SpriteFrames::set_animation_speed(const StringName &p_anim, float p_fps) {
 
-	ERR_FAIL_COND(p_fps < 0);
+	ERR_FAIL_COND_MSG(p_fps < 0, "Animation speed cannot be negative (" + itos(p_fps) + ").");
 	Map<StringName, Anim>::Element *E = animations.find(p_anim);
-	ERR_FAIL_COND(!E);
+	ERR_FAIL_COND_MSG(!E, "Animation '" + String(p_anim) + "' doesn't exist.");
 	E->get().speed = p_fps;
 }
 float SpriteFrames::get_animation_speed(const StringName &p_anim) const {
 
 	const Map<StringName, Anim>::Element *E = animations.find(p_anim);
-	ERR_FAIL_COND_V(!E, 0);
+	ERR_FAIL_COND_V_MSG(!E, 0, "Animation '" + String(p_anim) + "' doesn't exist.");
 	return E->get().speed;
 }
 
 void SpriteFrames::set_animation_loop(const StringName &p_anim, bool p_loop) {
 	Map<StringName, Anim>::Element *E = animations.find(p_anim);
-	ERR_FAIL_COND(!E);
+	ERR_FAIL_COND_MSG(!E, "Animation '" + String(p_anim) + "' doesn't exist.");
 	E->get().loop = p_loop;
 }
 bool SpriteFrames::get_animation_loop(const StringName &p_anim) const {
 	const Map<StringName, Anim>::Element *E = animations.find(p_anim);
-	ERR_FAIL_COND_V(!E, false);
+	ERR_FAIL_COND_V_MSG(!E, false, "Animation '" + String(p_anim) + "' doesn't exist.");
 	return E->get().loop;
 }
 
diff --git a/scene/2d/animated_sprite.h b/scene/2d/animated_sprite.h
index 2cc372bd93..3192d44678 100644
--- a/scene/2d/animated_sprite.h
+++ b/scene/2d/animated_sprite.h
@@ -85,7 +85,7 @@ public:
 	_FORCE_INLINE_ Ref<Texture> get_frame(const StringName &p_anim, int p_idx) const {
 
 		const Map<StringName, Anim>::Element *E = animations.find(p_anim);
-		ERR_FAIL_COND_V(!E, Ref<Texture>());
+		ERR_FAIL_COND_V_MSG(!E, Ref<Texture>(), "Animation '" + String(p_anim) + "' doesn't exist.");
 		ERR_FAIL_COND_V(p_idx < 0, Ref<Texture>());
 		if (p_idx >= E->get().frames.size())
 			return Ref<Texture>();
@@ -96,7 +96,7 @@ public:
 	_FORCE_INLINE_ Ref<Texture> get_normal_frame(const StringName &p_anim, int p_idx) const {
 
 		const Map<StringName, Anim>::Element *E = animations.find(p_anim);
-		ERR_FAIL_COND_V(!E, Ref<Texture>());
+		ERR_FAIL_COND_V_MSG(!E, Ref<Texture>(), "Animation '" + String(p_anim) + "' doesn't exist.");
 		ERR_FAIL_COND_V(p_idx < 0, Ref<Texture>());
 
 		const Map<StringName, Anim>::Element *EN = animations.find(E->get().normal_name);
@@ -109,7 +109,7 @@ public:
 
 	void set_frame(const StringName &p_anim, int p_idx, const Ref<Texture> &p_frame) {
 		Map<StringName, Anim>::Element *E = animations.find(p_anim);
-		ERR_FAIL_COND(!E);
+		ERR_FAIL_COND_MSG(!E, "Animation '" + String(p_anim) + "' doesn't exist.");
 		ERR_FAIL_COND(p_idx < 0);
 		if (p_idx >= E->get().frames.size())
 			return;
diff --git a/scene/2d/area_2d.cpp b/scene/2d/area_2d.cpp
index a636eea285..66a1318cb7 100644
--- a/scene/2d/area_2d.cpp
+++ b/scene/2d/area_2d.cpp
@@ -438,7 +438,7 @@ bool Area2D::is_monitorable() const {
 
 Array Area2D::get_overlapping_bodies() const {
 
-	ERR_FAIL_COND_V(!monitoring, Array());
+	ERR_FAIL_COND_V_MSG(!monitoring, Array(), "Can't find overlapping bodies when monitoring is off.");
 	Array ret;
 	ret.resize(body_map.size());
 	int idx = 0;
@@ -456,7 +456,7 @@ Array Area2D::get_overlapping_bodies() const {
 
 Array Area2D::get_overlapping_areas() const {
 
-	ERR_FAIL_COND_V(!monitoring, Array());
+	ERR_FAIL_COND_V_MSG(!monitoring, Array(), "Can't find overlapping bodies when monitoring is off.");
 	Array ret;
 	ret.resize(area_map.size());
 	int idx = 0;
diff --git a/scene/2d/cpu_particles_2d.cpp b/scene/2d/cpu_particles_2d.cpp
index f9f273d494..e1009d9a6c 100644
--- a/scene/2d/cpu_particles_2d.cpp
+++ b/scene/2d/cpu_particles_2d.cpp
@@ -44,7 +44,7 @@ void CPUParticles2D::set_emitting(bool p_emitting) {
 
 void CPUParticles2D::set_amount(int p_amount) {
 
-	ERR_FAIL_COND(p_amount < 1);
+	ERR_FAIL_COND_MSG(p_amount < 1, "Amount of particles must be greater than 0.");
 
 	particles.resize(p_amount);
 	{
@@ -62,7 +62,7 @@ void CPUParticles2D::set_amount(int p_amount) {
 }
 void CPUParticles2D::set_lifetime(float p_lifetime) {
 
-	ERR_FAIL_COND(p_lifetime <= 0);
+	ERR_FAIL_COND_MSG(p_lifetime <= 0, "Particles lifetime must be greater than 0.");
 	lifetime = p_lifetime;
 }
 
@@ -1122,8 +1122,9 @@ void CPUParticles2D::_notification(int p_what) {
 }
 
 void CPUParticles2D::convert_from_particles(Node *p_particles) {
+
 	Particles2D *particles = Object::cast_to<Particles2D>(p_particles);
-	ERR_FAIL_COND(!particles);
+	ERR_FAIL_COND_MSG(!particles, "Only Particles2D nodes can be converted to CPUParticles2D.");
 
 	set_emitting(particles->is_emitting());
 	set_amount(particles->get_amount());
diff --git a/scene/2d/particles_2d.cpp b/scene/2d/particles_2d.cpp
index 93c12f0103..0bf8237d37 100644
--- a/scene/2d/particles_2d.cpp
+++ b/scene/2d/particles_2d.cpp
@@ -51,13 +51,13 @@ void Particles2D::set_emitting(bool p_emitting) {
 
 void Particles2D::set_amount(int p_amount) {
 
-	ERR_FAIL_COND(p_amount < 1);
+	ERR_FAIL_COND_MSG(p_amount < 1, "Amount of particles cannot be smaller than 1.");
 	amount = p_amount;
 	VS::get_singleton()->particles_set_amount(particles, amount);
 }
 void Particles2D::set_lifetime(float p_lifetime) {
 
-	ERR_FAIL_COND(p_lifetime <= 0);
+	ERR_FAIL_COND_MSG(p_lifetime <= 0, "Particles lifetime must be greater than 0.");
 	lifetime = p_lifetime;
 	VS::get_singleton()->particles_set_lifetime(particles, lifetime);
 }
diff --git a/scene/2d/physics_body_2d.cpp b/scene/2d/physics_body_2d.cpp
index 9b6020e0fd..cea6a782d3 100644
--- a/scene/2d/physics_body_2d.cpp
+++ b/scene/2d/physics_body_2d.cpp
@@ -199,7 +199,7 @@ void StaticBody2D::set_friction(real_t p_friction) {
 
 	WARN_DEPRECATED_MSG("The method set_friction has been deprecated and will be removed in the future, use physics material instead.");
 
-	ERR_FAIL_COND(p_friction < 0 || p_friction > 1);
+	ERR_FAIL_COND_MSG(p_friction < 0 || p_friction > 1, "Friction must be between 0 and 1.");
 
 	if (physics_material_override.is_null()) {
 		physics_material_override.instance();
@@ -227,7 +227,7 @@ void StaticBody2D::set_bounce(real_t p_bounce) {
 
 	WARN_DEPRECATED_MSG("The method set_bounce has been deprecated and will be removed in the future, use physics material instead.");
 
-	ERR_FAIL_COND(p_bounce < 0 || p_bounce > 1);
+	ERR_FAIL_COND_MSG(p_bounce < 0 || p_bounce > 1, "Bounce must be between 0 and 1.");
 
 	if (physics_material_override.is_null()) {
 		physics_material_override.instance();
@@ -622,7 +622,7 @@ void RigidBody2D::set_friction(real_t p_friction) {
 
 	WARN_DEPRECATED_MSG("The method set_friction has been deprecated and will be removed in the future, use physics material instead.");
 
-	ERR_FAIL_COND(p_friction < 0 || p_friction > 1);
+	ERR_FAIL_COND_MSG(p_friction < 0 || p_friction > 1, "Friction must be between 0 and 1.");
 
 	if (physics_material_override.is_null()) {
 		physics_material_override.instance();
diff --git a/scene/2d/sprite.cpp b/scene/2d/sprite.cpp
index d7a8005187..af9ce2a4bf 100644
--- a/scene/2d/sprite.cpp
+++ b/scene/2d/sprite.cpp
@@ -281,7 +281,7 @@ Vector2 Sprite::get_frame_coords() const {
 
 void Sprite::set_vframes(int p_amount) {
 
-	ERR_FAIL_COND(p_amount < 1);
+	ERR_FAIL_COND_MSG(p_amount < 1, "Amount of vframes cannot be smaller than 1.");
 	vframes = p_amount;
 	update();
 	item_rect_changed();
@@ -294,7 +294,7 @@ int Sprite::get_vframes() const {
 
 void Sprite::set_hframes(int p_amount) {
 
-	ERR_FAIL_COND(p_amount < 1);
+	ERR_FAIL_COND_MSG(p_amount < 1, "Amount of hframes cannot be smaller than 1.");
 	hframes = p_amount;
 	update();
 	item_rect_changed();
diff --git a/scene/2d/tile_map.cpp b/scene/2d/tile_map.cpp
index 15423f8c5e..c0c1d8f691 100644
--- a/scene/2d/tile_map.cpp
+++ b/scene/2d/tile_map.cpp
@@ -216,7 +216,7 @@ Size2 TileMap::get_cell_size() const {
 
 void TileMap::set_quadrant_size(int p_size) {
 
-	ERR_FAIL_COND(p_size < 1);
+	ERR_FAIL_COND_MSG(p_size < 1, "Quadrant size cannot be smaller than 1.");
 
 	_clear_quadrants();
 	quadrant_size = p_size;
diff --git a/scene/3d/baked_lightmap.cpp b/scene/3d/baked_lightmap.cpp
index c5ff4dadbc..c78c62a5e2 100644
--- a/scene/3d/baked_lightmap.cpp
+++ b/scene/3d/baked_lightmap.cpp
@@ -88,7 +88,7 @@ float BakedLightmapData::get_energy() const {
 
 void BakedLightmapData::add_user(const NodePath &p_path, const Ref<Texture> &p_lightmap, int p_instance) {
 
-	ERR_FAIL_COND(p_lightmap.is_null());
+	ERR_FAIL_COND_MSG(p_lightmap.is_null(), "It's not a reference to a valid Texture object.");
 	User user;
 	user.path = p_path;
 	user.lightmap = p_lightmap;
@@ -359,7 +359,7 @@ BakedLightmap::BakeError BakedLightmap::bake(Node *p_from_node, bool p_create_vi
 		//check for valid save path
 		DirAccessRef d = DirAccess::open(save_path);
 		if (!d) {
-			ERR_PRINTS("Invalid Save Path: " + save_path);
+			ERR_PRINTS("Invalid Save Path '" + save_path + "'.");
 			return BAKE_ERROR_NO_SAVE_PATH;
 		}
 	}
diff --git a/scene/3d/cpu_particles.cpp b/scene/3d/cpu_particles.cpp
index fc16bc36cb..97688c46b4 100644
--- a/scene/3d/cpu_particles.cpp
+++ b/scene/3d/cpu_particles.cpp
@@ -53,7 +53,7 @@ void CPUParticles::set_emitting(bool p_emitting) {
 
 void CPUParticles::set_amount(int p_amount) {
 
-	ERR_FAIL_COND(p_amount < 1);
+	ERR_FAIL_COND_MSG(p_amount < 1, "Amount of particles must be greater than 0.");
 
 	particles.resize(p_amount);
 	{
@@ -71,7 +71,7 @@ void CPUParticles::set_amount(int p_amount) {
 }
 void CPUParticles::set_lifetime(float p_lifetime) {
 
-	ERR_FAIL_COND(p_lifetime <= 0);
+	ERR_FAIL_COND_MSG(p_lifetime <= 0, "Particles lifetime must be greater than 0.");
 	lifetime = p_lifetime;
 }
 
@@ -1193,7 +1193,7 @@ void CPUParticles::_notification(int p_what) {
 void CPUParticles::convert_from_particles(Node *p_particles) {
 
 	Particles *particles = Object::cast_to<Particles>(p_particles);
-	ERR_FAIL_COND(!particles);
+	ERR_FAIL_COND_MSG(!particles, "Only Particles nodes can be converted to CPUParticles.");
 
 	set_emitting(particles->is_emitting());
 	set_amount(particles->get_amount());
diff --git a/scene/3d/navigation.cpp b/scene/3d/navigation.cpp
index 12d562c0c6..ba0460d47c 100644
--- a/scene/3d/navigation.cpp
+++ b/scene/3d/navigation.cpp
@@ -230,7 +230,7 @@ void Navigation::navmesh_set_transform(int p_id, const Transform &p_xform) {
 }
 void Navigation::navmesh_remove(int p_id) {
 
-	ERR_FAIL_COND(!navmesh_map.has(p_id));
+	ERR_FAIL_COND_MSG(!navmesh_map.has(p_id), "Trying to remove nonexisting navmesh with id: " + itos(p_id));
 	_navmesh_unlink(p_id);
 	navmesh_map.erase(p_id);
 }
diff --git a/scene/3d/particles.cpp b/scene/3d/particles.cpp
index a6ccdb5791..241eb7d1ca 100644
--- a/scene/3d/particles.cpp
+++ b/scene/3d/particles.cpp
@@ -57,13 +57,13 @@ void Particles::set_emitting(bool p_emitting) {
 
 void Particles::set_amount(int p_amount) {
 
-	ERR_FAIL_COND(p_amount < 1);
+	ERR_FAIL_COND_MSG(p_amount < 1, "Amount of particles cannot be smaller than 1.");
 	amount = p_amount;
 	VS::get_singleton()->particles_set_amount(particles, amount);
 }
 void Particles::set_lifetime(float p_lifetime) {
 
-	ERR_FAIL_COND(p_lifetime <= 0);
+	ERR_FAIL_COND_MSG(p_lifetime <= 0, "Particles lifetime must be greater than 0.");
 	lifetime = p_lifetime;
 	VS::get_singleton()->particles_set_lifetime(particles, lifetime);
 }
diff --git a/scene/3d/physics_body.cpp b/scene/3d/physics_body.cpp
index 0756be5fc8..ea2bb2a21e 100644
--- a/scene/3d/physics_body.cpp
+++ b/scene/3d/physics_body.cpp
@@ -188,7 +188,7 @@ void StaticBody::set_friction(real_t p_friction) {
 
 	WARN_DEPRECATED_MSG("The method set_friction has been deprecated and will be removed in the future, use physics material instead.");
 
-	ERR_FAIL_COND(p_friction < 0 || p_friction > 1);
+	ERR_FAIL_COND_MSG(p_friction < 0 || p_friction > 1, "Friction must be between 0 and 1.");
 
 	if (physics_material_override.is_null()) {
 		physics_material_override.instance();
@@ -216,7 +216,7 @@ void StaticBody::set_bounce(real_t p_bounce) {
 
 	WARN_DEPRECATED_MSG("The method set_bounce has been deprecated and will be removed in the future, use physics material instead.");
 
-	ERR_FAIL_COND(p_bounce < 0 || p_bounce > 1);
+	ERR_FAIL_COND_MSG(p_bounce < 0 || p_bounce > 1, "Bounce must be between 0 and 1.");
 
 	if (physics_material_override.is_null()) {
 		physics_material_override.instance();
diff --git a/scene/animation/animation_cache.cpp b/scene/animation/animation_cache.cpp
index e26bd5b5a1..5956609244 100644
--- a/scene/animation/animation_cache.cpp
+++ b/scene/animation/animation_cache.cpp
@@ -80,7 +80,7 @@ void AnimationCache::_update_cache() {
 		if (!node) {
 
 			path_cache.push_back(Path());
-			ERR_CONTINUE_MSG(!node, "Invalid track path in animation: " + np + ".");
+			ERR_CONTINUE_MSG(!node, "Invalid track path in animation '" + np + "'.");
 		}
 
 		Path path;
@@ -91,7 +91,7 @@ void AnimationCache::_update_cache() {
 
 			if (np.get_subname_count() > 1) {
 				path_cache.push_back(Path());
-				ERR_CONTINUE_MSG(animation->track_get_type(i) == Animation::TYPE_TRANSFORM, "Transform tracks can't have a subpath: " + np + ".");
+				ERR_CONTINUE_MSG(animation->track_get_type(i) == Animation::TYPE_TRANSFORM, "Transform tracks can't have a subpath '" + np + "'.");
 			}
 
 			Spatial *sp = Object::cast_to<Spatial>(node);
@@ -99,7 +99,7 @@ void AnimationCache::_update_cache() {
 			if (!sp) {
 
 				path_cache.push_back(Path());
-				ERR_CONTINUE_MSG(!sp, "Transform track not of type Spatial: " + np + ".");
+				ERR_CONTINUE_MSG(!sp, "Transform track not of type Spatial '" + np + "'.");
 			}
 
 			if (np.get_subname_count() == 1) {
@@ -110,13 +110,13 @@ void AnimationCache::_update_cache() {
 				if (!sk) {
 
 					path_cache.push_back(Path());
-					ERR_CONTINUE_MSG(!sk, "Property defined in Transform track, but not a Skeleton!: " + np + ".");
+					ERR_CONTINUE_MSG(!sk, "Property defined in Transform track, but not a Skeleton! '" + np + "'.");
 				}
 
 				int idx = sk->find_bone(ps);
 				if (idx == -1) {
 					path_cache.push_back(Path());
-					ERR_CONTINUE_MSG(idx == -1, "Property defined in Transform track, but not a Skeleton Bone!: " + np + ".");
+					ERR_CONTINUE_MSG(idx == -1, "Property defined in Transform track, but not a Skeleton Bone! '" + np + "'.");
 				}
 
 				path.bone_idx = idx;
diff --git a/scene/animation/animation_player.cpp b/scene/animation/animation_player.cpp
index 051f832882..a31cf0ab39 100644
--- a/scene/animation/animation_player.cpp
+++ b/scene/animation/animation_player.cpp
@@ -1098,7 +1098,7 @@ void AnimationPlayer::get_animation_list(List<StringName> *p_animations) const {
 
 void AnimationPlayer::set_blend_time(const StringName &p_animation1, const StringName &p_animation2, float p_time) {
 
-	ERR_FAIL_COND(p_time < 0);
+	ERR_FAIL_COND_MSG(p_time < 0, "Blend time cannot be smaller than 0.");
 
 	BlendKey bk;
 	bk.from = p_animation1;
diff --git a/scene/gui/text_edit.cpp b/scene/gui/text_edit.cpp
index 7bcef5f9ab..e18442df66 100644
--- a/scene/gui/text_edit.cpp
+++ b/scene/gui/text_edit.cpp
@@ -6027,7 +6027,7 @@ bool TextEdit::is_indent_using_spaces() const {
 }
 
 void TextEdit::set_indent_size(const int p_size) {
-	ERR_FAIL_COND(p_size <= 0);
+	ERR_FAIL_COND_MSG(p_size <= 0, "Indend size must be greater than 0.");
 	indent_size = p_size;
 	text.set_indent_size(p_size);
 
diff --git a/scene/main/node.cpp b/scene/main/node.cpp
index bd01ca2886..2eec38fe63 100644
--- a/scene/main/node.cpp
+++ b/scene/main/node.cpp
@@ -2171,7 +2171,7 @@ void Node::_duplicate_and_reown(Node *p_new_parent, const Map<Node *, Node *> &p
 	if (get_filename() != "") {
 
 		Ref<PackedScene> res = ResourceLoader::load(get_filename());
-		ERR_FAIL_COND(res.is_null());
+		ERR_FAIL_COND_MSG(res.is_null(), "Cannot load scene: " + get_filename());
 		node = res->instance();
 		ERR_FAIL_COND(!node);
 	} else {
diff --git a/scene/main/viewport.cpp b/scene/main/viewport.cpp
index b5c82ce4e3..04278b2902 100644
--- a/scene/main/viewport.cpp
+++ b/scene/main/viewport.cpp
@@ -98,22 +98,22 @@ NodePath ViewportTexture::get_viewport_path_in_scene() const {
 
 int ViewportTexture::get_width() const {
 
-	ERR_FAIL_COND_V(!vp, 0);
+	ERR_FAIL_COND_V_MSG(!vp, 0, "Viewport Texture must be set to use it.");
 	return vp->size.width;
 }
 int ViewportTexture::get_height() const {
 
-	ERR_FAIL_COND_V(!vp, 0);
+	ERR_FAIL_COND_V_MSG(!vp, 0, "Viewport Texture must be set to use it.");
 	return vp->size.height;
 }
 Size2 ViewportTexture::get_size() const {
 
-	ERR_FAIL_COND_V(!vp, Size2());
+	ERR_FAIL_COND_V_MSG(!vp, Size2(), "Viewport Texture must be set to use it.");
 	return vp->size;
 }
 RID ViewportTexture::get_rid() const {
 
-	//ERR_FAIL_COND_V(!vp, RID());
+	//ERR_FAIL_COND_V_MSG(!vp, RID(), "Viewport Texture must be set to use it.");
 	return proxy;
 }
 
@@ -123,7 +123,7 @@ bool ViewportTexture::has_alpha() const {
 }
 Ref<Image> ViewportTexture::get_data() const {
 
-	ERR_FAIL_COND_V(!vp, Ref<Image>());
+	ERR_FAIL_COND_V_MSG(!vp, Ref<Image>(), "Viewport Texture must be set to use it.");
 	return VS::get_singleton()->texture_get_data(vp->texture_rid);
 }
 void ViewportTexture::set_flags(uint32_t p_flags) {
diff --git a/scene/resources/dynamic_font.cpp b/scene/resources/dynamic_font.cpp
index 2364a4a8a3..5704212831 100644
--- a/scene/resources/dynamic_font.cpp
+++ b/scene/resources/dynamic_font.cpp
@@ -130,7 +130,7 @@ Error DynamicFontAtSize::_load() {
 		} else {
 
 			FileAccess *f = FileAccess::open(font->font_path, FileAccess::READ);
-			ERR_FAIL_COND_V(!f, ERR_CANT_OPEN);
+			ERR_FAIL_COND_V_MSG(!f, ERR_CANT_OPEN, "Cannot open font file '" + font->font_path + "'.");
 
 			size_t len = f->get_len();
 			_fontdata[font->font_path] = Vector<uint8_t>();
@@ -145,7 +145,7 @@ Error DynamicFontAtSize::_load() {
 	if (font->font_mem == NULL && font->font_path != String()) {
 
 		FileAccess *f = FileAccess::open(font->font_path, FileAccess::READ);
-		ERR_FAIL_COND_V(!f, ERR_CANT_OPEN);
+		ERR_FAIL_COND_V_MSG(!f, ERR_CANT_OPEN, "Cannot open font file '" + font->font_path + "'.");
 
 		memset(&stream, 0, sizeof(FT_StreamRec));
 		stream.base = NULL;
@@ -182,17 +182,16 @@ Error DynamicFontAtSize::_load() {
 	//error = FT_New_Face( library, src_path.utf8().get_data(),0,&face );
 
 	if (error == FT_Err_Unknown_File_Format) {
-		ERR_EXPLAIN("Unknown font format.");
+
 		FT_Done_FreeType(library);
+		ERR_FAIL_V_MSG(ERR_FILE_CANT_OPEN, "Unknown font format.");
 
 	} else if (error) {
 
-		ERR_EXPLAIN("Error loading font.");
 		FT_Done_FreeType(library);
+		ERR_FAIL_V_MSG(ERR_FILE_CANT_OPEN, "Error loading font.");
 	}
 
-	ERR_FAIL_COND_V(error, ERR_FILE_CANT_OPEN);
-
 	if (FT_HAS_COLOR(face)) {
 		int best_match = 0;
 		int diff = ABS(id.size - ((int64_t)face->available_sizes[0].width));
diff --git a/scene/resources/dynamic_font_stb.cpp b/scene/resources/dynamic_font_stb.cpp
index ccff617a16..412bffa5dc 100644
--- a/scene/resources/dynamic_font_stb.cpp
+++ b/scene/resources/dynamic_font_stb.cpp
@@ -480,7 +480,7 @@ RES ResourceFormatLoaderDynamicFont::load(const String &p_path, const String &p_
 		*r_error = ERR_FILE_CANT_OPEN;
 
 	FileAccess *f = FileAccess::open(p_path, FileAccess::READ);
-	ERR_FAIL_COND_V(!f, RES());
+	ERR_FAIL_COND_V_MSG(!f, RES(), "Cannot load font from file '" + p_path + "'.");
 
 	PoolVector<uint8_t> data;
 
diff --git a/scene/resources/font.cpp b/scene/resources/font.cpp
index cff77acdd7..c94e143580 100644
--- a/scene/resources/font.cpp
+++ b/scene/resources/font.cpp
@@ -358,7 +358,7 @@ float BitmapFont::get_descent() const {
 
 void BitmapFont::add_texture(const Ref<Texture> &p_texture) {
 
-	ERR_FAIL_COND(p_texture.is_null());
+	ERR_FAIL_COND_MSG(p_texture.is_null(), "It's not a reference to a valid Texture object.");
 	textures.push_back(p_texture);
 }
 
diff --git a/scene/resources/mesh_library.cpp b/scene/resources/mesh_library.cpp
index d40a5dee2e..ad8da63abf 100644
--- a/scene/resources/mesh_library.cpp
+++ b/scene/resources/mesh_library.cpp
@@ -117,7 +117,7 @@ void MeshLibrary::create_item(int p_item) {
 
 void MeshLibrary::set_item_name(int p_item, const String &p_name) {
 
-	ERR_FAIL_COND(!item_map.has(p_item));
+	ERR_FAIL_COND_MSG(!item_map.has(p_item), "Requested for nonexistent MeshLibrary item '" + itos(p_item) + "'.");
 	item_map[p_item].name = p_name;
 	emit_changed();
 	_change_notify();
@@ -125,7 +125,7 @@ void MeshLibrary::set_item_name(int p_item, const String &p_name) {
 
 void MeshLibrary::set_item_mesh(int p_item, const Ref<Mesh> &p_mesh) {
 
-	ERR_FAIL_COND(!item_map.has(p_item));
+	ERR_FAIL_COND_MSG(!item_map.has(p_item), "Requested for nonexistent MeshLibrary item '" + itos(p_item) + "'.");
 	item_map[p_item].mesh = p_mesh;
 	notify_change_to_owners();
 	emit_changed();
@@ -134,7 +134,7 @@ void MeshLibrary::set_item_mesh(int p_item, const Ref<Mesh> &p_mesh) {
 
 void MeshLibrary::set_item_shapes(int p_item, const Vector<ShapeData> &p_shapes) {
 
-	ERR_FAIL_COND(!item_map.has(p_item));
+	ERR_FAIL_COND_MSG(!item_map.has(p_item), "Requested for nonexistent MeshLibrary item '" + itos(p_item) + "'.");
 	item_map[p_item].shapes = p_shapes;
 	_change_notify();
 	notify_change_to_owners();
@@ -144,7 +144,7 @@ void MeshLibrary::set_item_shapes(int p_item, const Vector<ShapeData> &p_shapes)
 
 void MeshLibrary::set_item_navmesh(int p_item, const Ref<NavigationMesh> &p_navmesh) {
 
-	ERR_FAIL_COND(!item_map.has(p_item));
+	ERR_FAIL_COND_MSG(!item_map.has(p_item), "Requested for nonexistent MeshLibrary item '" + itos(p_item) + "'.");
 	item_map[p_item].navmesh = p_navmesh;
 	_change_notify();
 	notify_change_to_owners();
@@ -154,7 +154,7 @@ void MeshLibrary::set_item_navmesh(int p_item, const Ref<NavigationMesh> &p_navm
 
 void MeshLibrary::set_item_navmesh_transform(int p_item, const Transform &p_transform) {
 
-	ERR_FAIL_COND(!item_map.has(p_item));
+	ERR_FAIL_COND_MSG(!item_map.has(p_item), "Requested for nonexistent MeshLibrary item '" + itos(p_item) + "'.");
 	item_map[p_item].navmesh_transform = p_transform;
 	notify_change_to_owners();
 	emit_changed();
@@ -163,7 +163,7 @@ void MeshLibrary::set_item_navmesh_transform(int p_item, const Transform &p_tran
 
 void MeshLibrary::set_item_preview(int p_item, const Ref<Texture> &p_preview) {
 
-	ERR_FAIL_COND(!item_map.has(p_item));
+	ERR_FAIL_COND_MSG(!item_map.has(p_item), "Requested for nonexistent MeshLibrary item '" + itos(p_item) + "'.");
 	item_map[p_item].preview = p_preview;
 	emit_changed();
 	_change_notify();
@@ -171,37 +171,37 @@ void MeshLibrary::set_item_preview(int p_item, const Ref<Texture> &p_preview) {
 
 String MeshLibrary::get_item_name(int p_item) const {
 
-	ERR_FAIL_COND_V(!item_map.has(p_item), "");
+	ERR_FAIL_COND_V_MSG(!item_map.has(p_item), "", "Requested for nonexistent MeshLibrary item '" + itos(p_item) + "'.");
 	return item_map[p_item].name;
 }
 
 Ref<Mesh> MeshLibrary::get_item_mesh(int p_item) const {
 
-	ERR_FAIL_COND_V(!item_map.has(p_item), Ref<Mesh>());
+	ERR_FAIL_COND_V_MSG(!item_map.has(p_item), Ref<Mesh>(), "Requested for nonexistent MeshLibrary item '" + itos(p_item) + "'.");
 	return item_map[p_item].mesh;
 }
 
 Vector<MeshLibrary::ShapeData> MeshLibrary::get_item_shapes(int p_item) const {
 
-	ERR_FAIL_COND_V(!item_map.has(p_item), Vector<ShapeData>());
+	ERR_FAIL_COND_V_MSG(!item_map.has(p_item), Vector<ShapeData>(), "Requested for nonexistent MeshLibrary item '" + itos(p_item) + "'.");
 	return item_map[p_item].shapes;
 }
 
 Ref<NavigationMesh> MeshLibrary::get_item_navmesh(int p_item) const {
 
-	ERR_FAIL_COND_V(!item_map.has(p_item), Ref<NavigationMesh>());
+	ERR_FAIL_COND_V_MSG(!item_map.has(p_item), Ref<NavigationMesh>(), "Requested for nonexistent MeshLibrary item '" + itos(p_item) + "'.");
 	return item_map[p_item].navmesh;
 }
 
 Transform MeshLibrary::get_item_navmesh_transform(int p_item) const {
 
-	ERR_FAIL_COND_V(!item_map.has(p_item), Transform());
+	ERR_FAIL_COND_V_MSG(!item_map.has(p_item), Transform(), "Requested for nonexistent MeshLibrary item '" + itos(p_item) + "'.");
 	return item_map[p_item].navmesh_transform;
 }
 
 Ref<Texture> MeshLibrary::get_item_preview(int p_item) const {
 
-	ERR_FAIL_COND_V(!item_map.has(p_item), Ref<Texture>());
+	ERR_FAIL_COND_V_MSG(!item_map.has(p_item), Ref<Texture>(), "Requested for nonexistent MeshLibrary item '" + itos(p_item) + "'.");
 	return item_map[p_item].preview;
 }
 
@@ -211,7 +211,7 @@ bool MeshLibrary::has_item(int p_item) const {
 }
 void MeshLibrary::remove_item(int p_item) {
 
-	ERR_FAIL_COND(!item_map.has(p_item));
+	ERR_FAIL_COND_MSG(!item_map.has(p_item), "Requested for nonexistent MeshLibrary item '" + itos(p_item) + "'.");
 	item_map.erase(p_item);
 	notify_change_to_owners();
 	_change_notify();
diff --git a/scene/resources/resource_format_text.cpp b/scene/resources/resource_format_text.cpp
index cd229732ba..89712db9f4 100644
--- a/scene/resources/resource_format_text.cpp
+++ b/scene/resources/resource_format_text.cpp
@@ -1225,7 +1225,7 @@ Ref<ResourceInteractiveLoader> ResourceFormatLoaderText::load_interactive(const
 	Error err;
 	FileAccess *f = FileAccess::open(p_path, FileAccess::READ, &err);
 
-	ERR_FAIL_COND_V(err != OK, Ref<ResourceInteractiveLoader>());
+	ERR_FAIL_COND_V_MSG(err != OK, Ref<ResourceInteractiveLoader>(), "Cannot open file '" + p_path + "'.");
 
 	Ref<ResourceInteractiveLoaderText> ria = memnew(ResourceInteractiveLoaderText);
 	String path = p_original_path != "" ? p_original_path : p_path;
@@ -1321,7 +1321,7 @@ Error ResourceFormatLoaderText::convert_file_to_binary(const String &p_src_path,
 	Error err;
 	FileAccess *f = FileAccess::open(p_src_path, FileAccess::READ, &err);
 
-	ERR_FAIL_COND_V(err != OK, ERR_CANT_OPEN);
+	ERR_FAIL_COND_V_MSG(err != OK, ERR_CANT_OPEN, "Cannot open file '" + p_src_path + "'.");
 
 	Ref<ResourceInteractiveLoaderText> ria = memnew(ResourceInteractiveLoaderText);
 	const String &path = p_src_path;
@@ -1481,7 +1481,7 @@ Error ResourceFormatSaverTextInstance::save(const String &p_path, const RES &p_r
 
 	Error err;
 	f = FileAccess::open(p_path, FileAccess::WRITE, &err);
-	ERR_FAIL_COND_V(err, ERR_CANT_OPEN);
+	ERR_FAIL_COND_V_MSG(err, ERR_CANT_OPEN, "Cannot save file '" + p_path + "'.");
 	FileAccessRef _fref(f);
 
 	local_path = ProjectSettings::get_singleton()->localize_path(p_path);
diff --git a/scene/resources/shader.cpp b/scene/resources/shader.cpp
index 89570beb5f..57e2470164 100644
--- a/scene/resources/shader.cpp
+++ b/scene/resources/shader.cpp
@@ -222,10 +222,7 @@ Error ResourceFormatSaverShader::save(const String &p_path, const RES &p_resourc
 	Error err;
 	FileAccess *file = FileAccess::open(p_path, FileAccess::WRITE, &err);
 
-	if (err) {
-
-		ERR_FAIL_COND_V(err, err);
-	}
+	ERR_FAIL_COND_V_MSG(err, err, "Cannot save shader '" + p_path + "'.");
 
 	file->store_string(source);
 	if (file->get_error() != OK && file->get_error() != ERR_FILE_EOF) {
diff --git a/scene/resources/text_file.cpp b/scene/resources/text_file.cpp
index b84f3f1f9e..3faedc883d 100644
--- a/scene/resources/text_file.cpp
+++ b/scene/resources/text_file.cpp
@@ -53,9 +53,8 @@ Error TextFile::load_text(const String &p_path) {
 	PoolVector<uint8_t> sourcef;
 	Error err;
 	FileAccess *f = FileAccess::open(p_path, FileAccess::READ, &err);
-	if (err) {
-		ERR_FAIL_COND_V(err, err);
-	}
+
+	ERR_FAIL_COND_V_MSG(err, err, "Cannot open TextFile '" + p_path + "'.");
 
 	int len = f->get_len();
 	sourcef.resize(len + 1);
diff --git a/scene/resources/texture.cpp b/scene/resources/texture.cpp
index e44b17584b..d15a972358 100644
--- a/scene/resources/texture.cpp
+++ b/scene/resources/texture.cpp
@@ -175,7 +175,7 @@ void ImageTexture::_reload_hook(const RID &p_hook) {
 	img.instance();
 	Error err = ImageLoader::load_image(path, img);
 
-	ERR_FAIL_COND(err != OK);
+	ERR_FAIL_COND_MSG(err != OK, "Cannot load image from path '" + path + "'.");
 
 	VisualServer::get_singleton()->texture_set_data(texture, img);
 
@@ -2355,7 +2355,7 @@ RES ResourceFormatLoaderTextureLayered::load(const String &p_path, const String
 	}
 
 	FileAccess *f = FileAccess::open(p_path, FileAccess::READ);
-	ERR_FAIL_COND_V(!f, RES());
+	ERR_FAIL_COND_V_MSG(!f, RES(), "Cannot open file '" + p_path + "'.");
 
 	uint8_t header[5] = { 0, 0, 0, 0, 0 };
 	f->get_buffer(header, 4);
@@ -2372,7 +2372,7 @@ RES ResourceFormatLoaderTextureLayered::load(const String &p_path, const String
 		}
 	} else {
 
-		ERR_FAIL_V_MSG(RES(), "Unrecognized layered texture file format: " + String((const char *)header) + ".");
+		ERR_FAIL_V_MSG(RES(), "Unrecognized layered texture file format '" + String((const char *)header) + "'.");
 	}
 
 	int tw = f->get_32();
diff --git a/servers/physics/collision_object_sw.h b/servers/physics/collision_object_sw.h
index b9912f0ba2..08708e2f60 100644
--- a/servers/physics/collision_object_sw.h
+++ b/servers/physics/collision_object_sw.h
@@ -88,7 +88,7 @@ protected:
 	_FORCE_INLINE_ void _set_transform(const Transform &p_transform, bool p_update_shapes = true) {
 #ifdef DEBUG_ENABLED
 
-		ERR_FAIL_COND_MSG(p_transform.origin.length_squared() > MAX_OBJECT_DISTANCE_X2, "Object went too far away (more than " + itos(MAX_OBJECT_DISTANCE) + " units from origin).");
+		ERR_FAIL_COND_MSG(p_transform.origin.length_squared() > MAX_OBJECT_DISTANCE_X2, "Object went too far away (more than '" + itos(MAX_OBJECT_DISTANCE) + "' units from origin).");
 #endif
 
 		transform = p_transform;