Implement Feature Build Profiles

This PR is a continuation of #50381 (which was implemented exactly a year ago!)

* Add a visual interface to select which classes should not be built into Godot (well, they are built if something else uses them, but if not used the optimizer will remove them out).
* Add a detection system to scan the project and figure out the actual classes used.
* Added the ability for SCons to load build profiles.

Obligatory Screen:

A simple test with a couple of nodes in the scene resulted in a 25% reduction for the final binary size

TODO:

* Script languages need to implement used class detection (left for another PR).
* Options to disable servers or server functionalities (like 2D or 3D physics, navigation, etc). Are missing, that should also greatly aid in reducing binary size.
* Options to disable some modules would be desired.
* More options to disable drivers (OpenGL, Vulkan, etc) would be desired.

In general this PR is a starting point for more contributors to improve and enhance this functionality.

9 files changed, 88 insertions, 8 deletions

diff --git a/core/io/resource_format_binary.cpp b/core/io/resource_format_binary.cpp
index b1c50e829c..0f4bc1e19c 100644
--- a/core/io/resource_format_binary.cpp
+++ b/core/io/resource_format_binary.cpp
@@ -865,6 +865,22 @@ String ResourceLoaderBinary::get_unicode_string() {
 	return s;
 }
 
+void ResourceLoaderBinary::get_classes_used(Ref<FileAccess> p_f, HashSet<StringName> *p_classes) {
+	open(p_f, false, true);
+	if (error) {
+		return;
+	}
+
+	for (int i = 0; i < internal_resources.size(); i++) {
+		p_f->seek(internal_resources[i].offset);
+		String t = get_unicode_string();
+		ERR_FAIL_COND(p_f->get_error() != OK);
+		if (t != String()) {
+			p_classes->insert(t);
+		}
+	}
+}
+
 void ResourceLoaderBinary::get_dependencies(Ref<FileAccess> p_f, List<String> *p_dependencies, bool p_add_types) {
 	open(p_f, false, true);
 	if (error) {
@@ -1337,6 +1353,16 @@ Error ResourceFormatLoaderBinary::rename_dependencies(const String &p_path, cons
 	return OK;
 }
 
+void ResourceFormatLoaderBinary::get_classes_used(const String &p_path, HashSet<StringName> *r_classes) {
+	Ref<FileAccess> f = FileAccess::open(p_path, FileAccess::READ);
+	ERR_FAIL_COND_MSG(f.is_null(), "Cannot open file '" + p_path + "'.");
+
+	ResourceLoaderBinary loader;
+	loader.local_path = ProjectSettings::get_singleton()->localize_path(p_path);
+	loader.res_path = loader.local_path;
+	loader.get_classes_used(f, r_classes);
+}
+
 String ResourceFormatLoaderBinary::get_resource_type(const String &p_path) const {
 	Ref<FileAccess> f = FileAccess::open(p_path, FileAccess::READ);
 	if (f.is_null()) {
diff --git a/core/io/resource_format_binary.h b/core/io/resource_format_binary.h
index 5da880ddb8..2b043302fd 100644
--- a/core/io/resource_format_binary.h
+++ b/core/io/resource_format_binary.h
@@ -101,6 +101,7 @@ public:
 	void open(Ref<FileAccess> p_f, bool p_no_resources = false, bool p_keep_uuid_paths = false);
 	String recognize(Ref<FileAccess> p_f);
 	void get_dependencies(Ref<FileAccess> p_f, List<String> *p_dependencies, bool p_add_types);
+	void get_classes_used(Ref<FileAccess> p_f, HashSet<StringName> *p_classes);
 
 	ResourceLoaderBinary() {}
 };
@@ -112,6 +113,7 @@ public:
 	virtual void get_recognized_extensions(List<String> *p_extensions) const;
 	virtual bool handles_type(const String &p_type) const;
 	virtual String get_resource_type(const String &p_path) const;
+	virtual void get_classes_used(const String &p_path, HashSet<StringName> *r_classes);
 	virtual ResourceUID::ID get_resource_uid(const String &p_path) const;
 	virtual void get_dependencies(const String &p_path, List<String> *p_dependencies, bool p_add_types = false);
 	virtual Error rename_dependencies(const String &p_path, const HashMap<String, String> &p_map);
diff --git a/core/io/resource_importer.cpp b/core/io/resource_importer.cpp
index 934cb780e6..e059fc842b 100644
--- a/core/io/resource_importer.cpp
+++ b/core/io/resource_importer.cpp
@@ -352,6 +352,16 @@ Variant ResourceFormatImporter::get_resource_metadata(const String &p_path) cons
 
 	return pat.metadata;
 }
+void ResourceFormatImporter::get_classes_used(const String &p_path, HashSet<StringName> *r_classes) {
+	PathAndType pat;
+	Error err = _get_path_and_type(p_path, pat);
+
+	if (err != OK) {
+		return;
+	}
+
+	ResourceLoader::get_classes_used(pat.path, r_classes);
+}
 
 void ResourceFormatImporter::get_dependencies(const String &p_path, List<String> *p_dependencies, bool p_add_types) {
 	PathAndType pat;
diff --git a/core/io/resource_importer.h b/core/io/resource_importer.h
index 0c7909df06..d0ea98b598 100644
--- a/core/io/resource_importer.h
+++ b/core/io/resource_importer.h
@@ -65,12 +65,12 @@ public:
 	virtual bool handles_type(const String &p_type) const;
 	virtual String get_resource_type(const String &p_path) const;
 	virtual ResourceUID::ID get_resource_uid(const String &p_path) const;
-
 	virtual Variant get_resource_metadata(const String &p_path) const;
 	virtual bool is_import_valid(const String &p_path) const;
 	virtual void get_dependencies(const String &p_path, List<String> *p_dependencies, bool p_add_types = false);
 	virtual bool is_imported(const String &p_path) const { return recognize_path(p_path); }
 	virtual String get_import_group_file(const String &p_path) const;
+	virtual void get_classes_used(const String &p_path, HashSet<StringName> *r_classes);
 	virtual bool exists(const String &p_path) const;
 
 	virtual int get_import_order(const String &p_path) const;
diff --git a/core/io/resource_loader.cpp b/core/io/resource_loader.cpp
index 2cd455475c..fc4177004b 100644
--- a/core/io/resource_loader.cpp
+++ b/core/io/resource_loader.cpp
@@ -76,6 +76,21 @@ bool ResourceFormatLoader::handles_type(const String &p_type) const {
 	return false;
 }
 
+void ResourceFormatLoader::get_classes_used(const String &p_path, HashSet<StringName> *r_classes) {
+	Vector<String> ret;
+	if (GDVIRTUAL_CALL(_get_classes_used, p_path, ret)) {
+		for (int i = 0; i < ret.size(); i++) {
+			r_classes->insert(ret[i]);
+		}
+		return;
+	}
+
+	String res = get_resource_type(p_path);
+	if (!res.is_empty()) {
+		r_classes->insert(res);
+	}
+}
+
 String ResourceFormatLoader::get_resource_type(const String &p_path) const {
 	String ret;
 
@@ -180,6 +195,7 @@ void ResourceFormatLoader::_bind_methods() {
 	GDVIRTUAL_BIND(_get_dependencies, "path", "add_types");
 	GDVIRTUAL_BIND(_rename_dependencies, "path", "renames");
 	GDVIRTUAL_BIND(_exists, "path");
+	GDVIRTUAL_BIND(_get_classes_used, "path");
 	GDVIRTUAL_BIND(_load, "path", "original_path", "use_sub_threads", "cache_mode");
 }
 
@@ -730,6 +746,18 @@ Error ResourceLoader::rename_dependencies(const String &p_path, const HashMap<St
 	return OK; // ??
 }
 
+void ResourceLoader::get_classes_used(const String &p_path, HashSet<StringName> *r_classes) {
+	String local_path = _validate_local_path(p_path);
+
+	for (int i = 0; i < loader_count; i++) {
+		if (!loader[i]->recognize_path(local_path)) {
+			continue;
+		}
+
+		return loader[i]->get_classes_used(p_path, r_classes);
+	}
+}
+
 String ResourceLoader::get_resource_type(const String &p_path) {
 	String local_path = _validate_local_path(p_path);
 
diff --git a/core/io/resource_loader.h b/core/io/resource_loader.h
index 815dd1dd72..91ba930176 100644
--- a/core/io/resource_loader.h
+++ b/core/io/resource_loader.h
@@ -55,6 +55,7 @@ protected:
 	GDVIRTUAL1RC(String, _get_resource_type, String)
 	GDVIRTUAL1RC(ResourceUID::ID, _get_resource_uid, String)
 	GDVIRTUAL2RC(Vector<String>, _get_dependencies, String, bool)
+	GDVIRTUAL1RC(Vector<String>, _get_classes_used, String)
 	GDVIRTUAL2RC(int64_t, _rename_dependencies, String, Dictionary)
 	GDVIRTUAL1RC(bool, _exists, String)
 
@@ -67,6 +68,7 @@ public:
 	virtual void get_recognized_extensions_for_type(const String &p_type, List<String> *p_extensions) const;
 	virtual bool recognize_path(const String &p_path, const String &p_for_type = String()) const;
 	virtual bool handles_type(const String &p_type) const;
+	virtual void get_classes_used(const String &p_path, HashSet<StringName> *r_classes);
 	virtual String get_resource_type(const String &p_path) const;
 	virtual ResourceUID::ID get_resource_uid(const String &p_path) const;
 	virtual void get_dependencies(const String &p_path, List<String> *p_dependencies, bool p_add_types = false);
@@ -170,6 +172,7 @@ public:
 	static void get_recognized_extensions_for_type(const String &p_type, List<String> *p_extensions);
 	static void add_resource_format_loader(Ref<ResourceFormatLoader> p_format_loader, bool p_at_front = false);
 	static void remove_resource_format_loader(Ref<ResourceFormatLoader> p_format_loader);
+	static void get_classes_used(const String &p_path, HashSet<StringName> *r_classes);
 	static String get_resource_type(const String &p_path);
 	static ResourceUID::ID get_resource_uid(const String &p_path);
 	static void get_dependencies(const String &p_path, List<String> *p_dependencies, bool p_add_types = false);
diff --git a/core/object/class_db.cpp b/core/object/class_db.cpp
index ac008dad88..d67315f20d 100644
--- a/core/object/class_db.cpp
+++ b/core/object/class_db.cpp
@@ -305,6 +305,13 @@ void ClassDB::add_compatibility_class(const StringName &p_class, const StringNam
 	compat_classes[p_class] = p_fallback;
 }
 
+StringName ClassDB::get_compatibility_class(const StringName &p_class) {
+	if (compat_classes.has(p_class)) {
+		return compat_classes[p_class];
+	}
+	return StringName();
+}
+
 Object *ClassDB::instantiate(const StringName &p_class) {
 	ClassInfo *ti;
 	{
diff --git a/core/object/class_db.h b/core/object/class_db.h
index 1d26eb18f1..8b6a260d86 100644
--- a/core/object/class_db.h
+++ b/core/object/class_db.h
@@ -357,6 +357,7 @@ public:
 	static bool is_resource_extension(const StringName &p_extension);
 
 	static void add_compatibility_class(const StringName &p_class, const StringName &p_fallback);
+	static StringName get_compatibility_class(const StringName &p_class);
 
 	static void set_current_api(APIType p_api);
 	static APIType get_current_api();
@@ -418,16 +419,16 @@ _FORCE_INLINE_ Vector<Error> errarray(P... p_args) {
 
 #endif
 
-#define GDREGISTER_CLASS(m_class)                    \
-	if (!GD_IS_DEFINED(ClassDB_Disable_##m_class)) { \
-		::ClassDB::register_class<m_class>();        \
+#define GDREGISTER_CLASS(m_class)             \
+	if (m_class::_class_is_enabled) {         \
+		::ClassDB::register_class<m_class>(); \
 	}
-#define GDREGISTER_VIRTUAL_CLASS(m_class)            \
-	if (!GD_IS_DEFINED(ClassDB_Disable_##m_class)) { \
-		::ClassDB::register_class<m_class>(true);    \
+#define GDREGISTER_VIRTUAL_CLASS(m_class)         \
+	if (m_class::_class_is_enabled) {             \
+		::ClassDB::register_class<m_class>(true); \
 	}
 #define GDREGISTER_ABSTRACT_CLASS(m_class)             \
-	if (!GD_IS_DEFINED(ClassDB_Disable_##m_class)) {   \
+	if (m_class::_class_is_enabled) {                  \
 		::ClassDB::register_abstract_class<m_class>(); \
 	}
 
diff --git a/core/object/object.h b/core/object/object.h
index 705d6451dc..17f75a4e1d 100644
--- a/core/object/object.h
+++ b/core/object/object.h
@@ -358,6 +358,7 @@ private:
 	friend class ::ClassDB;                                                                                                                      \
                                                                                                                                                  \
 public:                                                                                                                                          \
+	static constexpr bool _class_is_enabled = !bool(GD_IS_DEFINED(ClassDB_Disable_##m_class)) && m_inherits::_class_is_enabled;                  \
 	virtual String get_class() const override {                                                                                                  \
 		if (_get_extension()) {                                                                                                                  \
 			return _get_extension()->class_name.operator String();                                                                               \
@@ -667,6 +668,8 @@ public: // Should be protected, but bug in clang++.
 	_FORCE_INLINE_ static void register_custom_data_to_otdb() {}
 
 public:
+	static constexpr bool _class_is_enabled = true;
+
 	void notify_property_list_changed();
 
 	static void *get_class_ptr_static() {