ProjectManager: Warn when projects have different config_version

When opening projects for edition through the project manager, the
following checks are now done:

1. If the config_version is lower than the one used by the current
   engine version, users are asked if they want to convert to the new
   format or abort editing. Fixes #20626.
2. If the config_version is higher than the expected one (project
   from a more recent and incompatible engine version), projects are
   grayed out and can't be edited. Fixes #18758.

When editing from the command line, the behaviour is unchanged:
projects in situation (1) are automatically converted, while projects
in situation (2) show an error message (made more explicit).

The "Run" option from the project manager was not changed, so it will
still run (1) projects without converting them, and fail running (2)
projects.

Co-authored-by: groud <gilles.roudiere@gmail.com>

2 files changed, 14 insertions, 16 deletions

diff --git a/core/project_settings.cpp b/core/project_settings.cpp
index 031ac06063..f3368a5595 100644
--- a/core/project_settings.cpp
+++ b/core/project_settings.cpp
@@ -43,8 +43,6 @@
 
 #include <zlib.h>
 
-#define FORMAT_VERSION 4
-
 ProjectSettings *ProjectSettings::singleton = NULL;
 
 ProjectSettings *ProjectSettings::get_singleton() {
@@ -271,9 +269,9 @@ bool ProjectSettings::_load_resource_pack(const String &p_pack) {
 	return true;
 }
 
-void ProjectSettings::_convert_to_last_version() {
-	if (!has_setting("config_version") || (int)get_setting("config_version") <= 3) {
+void ProjectSettings::_convert_to_last_version(int p_from_version) {
 
+	if (p_from_version <= 3) {
 		// Converts the actions from array to dictionary (array of events to dictionary with deadzone + events)
 		for (Map<StringName, ProjectSettings::VariantContainer>::Element *E = props.front(); E; E = E->next()) {
 			Variant value = E->get().variant;
@@ -396,7 +394,6 @@ Error ProjectSettings::_setup(const String &p_path, const String &p_main_pack, b
 			// Optional, we don't mind if it fails
 			_load_settings_text("res://override.cfg");
 		}
-
 		return err;
 	}
 
@@ -443,10 +440,6 @@ Error ProjectSettings::_setup(const String &p_path, const String &p_main_pack, b
 	if (resource_path.length() && resource_path[resource_path.length() - 1] == '/')
 		resource_path = resource_path.substr(0, resource_path.length() - 1); // chop end
 
-	// If we're loading a project.godot from source code, we can operate some
-	// ProjectSettings conversions if need be.
-	_convert_to_last_version();
-
 	return OK;
 }
 
@@ -537,8 +530,8 @@ Error ProjectSettings::_load_settings_text(const String p_path) {
 
 	int lines = 0;
 	String error_text;
-
 	String section;
+	int config_version = 0;
 
 	while (true) {
 
@@ -549,6 +542,9 @@ Error ProjectSettings::_load_settings_text(const String p_path) {
 		err = VariantParser::parse_tag_assign_eof(&stream, lines, error_text, next_tag, assign, value, NULL, true);
 		if (err == ERR_FILE_EOF) {
 			memdelete(f);
+			// If we're loading a project.godot from source code, we can operate some
+			// ProjectSettings conversions if need be.
+			_convert_to_last_version(config_version);
 			return OK;
 		} else if (err != OK) {
 			ERR_PRINTS("Error parsing " + p_path + " at line " + itos(lines) + ": " + error_text + " File might be corrupted.");
@@ -558,13 +554,13 @@ Error ProjectSettings::_load_settings_text(const String p_path) {
 
 		if (assign != String()) {
 			if (section == String() && assign == "config_version") {
-				int config_version = value;
-				if (config_version > FORMAT_VERSION) {
+				config_version = value;
+				if (config_version > CONFIG_VERSION) {
 					memdelete(f);
-					ERR_FAIL_COND_V(config_version > FORMAT_VERSION, ERR_FILE_CANT_OPEN);
+					ERR_EXPLAIN(vformat("Can't open project at '%s', its `config_version` (%d) is from a more recent and incompatible version of the engine. Expected config version: %d.", p_path, config_version, CONFIG_VERSION));
+					ERR_FAIL_COND_V(config_version > CONFIG_VERSION, ERR_FILE_CANT_OPEN);
 				}
 			} else {
-				// config_version is checked and dropped
 				if (section == String()) {
 					set(assign, value);
 				} else {
@@ -740,7 +736,7 @@ Error ProjectSettings::_save_settings_text(const String &p_file, const Map<Strin
 	file->store_line(";   param=value ; assign values to parameters");
 	file->store_line("");
 
-	file->store_string("config_version=" + itos(FORMAT_VERSION) + "\n");
+	file->store_string("config_version=" + itos(CONFIG_VERSION) + "\n");
 	if (p_custom_features != String())
 		file->store_string("custom_features=\"" + p_custom_features + "\"\n");
 	file->store_string("\n");
diff --git a/core/project_settings.h b/core/project_settings.h
index c790669048..2cb159e1c7 100644
--- a/core/project_settings.h
+++ b/core/project_settings.h
@@ -106,7 +106,7 @@ protected:
 
 	Error _save_custom_bnd(const String &p_file);
 
-	void _convert_to_last_version();
+	void _convert_to_last_version(int p_from_version);
 
 	bool _load_resource_pack(const String &p_pack);
 
@@ -118,6 +118,8 @@ protected:
 	static void _bind_methods();
 
 public:
+	static const int CONFIG_VERSION = 4;
+
 	void set_setting(const String &p_setting, const Variant &p_value);
 	Variant get_setting(const String &p_setting) const;