Make add_importer and add_post_importer_plugin override existing importers.

core/io/resource_importer.cpp

@@ -463,3 +463,8 @@ void ResourceImporter::_bind_methods() {
 	BIND_ENUM_CONSTANT(IMPORT_ORDER_DEFAULT);
 	BIND_ENUM_CONSTANT(IMPORT_ORDER_SCENE);
 }
+
+void ResourceFormatImporter::add_importer(const Ref<ResourceImporter> &p_importer) {
+	ERR_FAIL_COND(p_importer.is_null());
+	importers.insert(0, p_importer);
+}

core/io/resource_importer.h

@@ -80,9 +80,8 @@ public:
 	String get_internal_resource_path(const String &p_path) const;
 	void get_internal_resource_path_list(const String &p_path, List<String> *r_paths);
 
-	void add_importer(const Ref<ResourceImporter> &p_importer) {
-		importers.push_back(p_importer);
-	}
+	void add_importer(const Ref<ResourceImporter> &p_importer);
+
 	void remove_importer(const Ref<ResourceImporter> &p_importer) { importers.erase(p_importer); }
 	Ref<ResourceImporter> get_importer_by_name(const String &p_name) const;
 	Ref<ResourceImporter> get_importer_by_extension(const String &p_extension) const;

editor/import/resource_importer_scene.cpp

@@ -258,8 +258,8 @@ String ResourceImporterScene::get_visible_name() const {
 }
 
 void ResourceImporterScene::get_recognized_extensions(List<String> *p_extensions) const {
-	for (Set<Ref<EditorSceneFormatImporter>>::Element *E = importers.front(); E; E = E->next()) {
-		E->get()->get_extensions(p_extensions);
+	for (Ref<EditorSceneFormatImporter> importer_elem : importers) {
+		importer_elem->get_extensions(p_extensions);
 	}
 }
 
@@ -1489,8 +1489,8 @@ void ResourceImporterScene::get_import_options(const String &p_path, List<Import
 		post_importer_plugins.write[i]->get_import_options(p_path, r_options);
 	}
 
-	for (Ref<EditorSceneFormatImporter> importer : importers) {
-		importer->get_import_options(p_path, r_options);
+	for (Ref<EditorSceneFormatImporter> importer_elem : importers) {
+		importer_elem->get_import_options(p_path, r_options);
 	}
 }
 
@@ -1841,13 +1841,13 @@ Node *ResourceImporterScene::pre_import(const String &p_source_file) {
 	EditorProgress progress("pre-import", TTR("Pre-Import Scene"), 0);
 	progress.step(TTR("Importing Scene..."), 0);
 
-	for (Set<Ref<EditorSceneFormatImporter>>::Element *E = importers.front(); E; E = E->next()) {
+	for (Ref<EditorSceneFormatImporter> importer_elem : importers) {
 		List<String> extensions;
-		E->get()->get_extensions(&extensions);
+		importer_elem->get_extensions(&extensions);
 
 		for (const String &F : extensions) {
 			if (F.to_lower() == ext) {
-				importer = E->get();
+				importer = importer_elem;
 				break;
 			}
 		}
@@ -1881,13 +1881,13 @@ Error ResourceImporterScene::import(const String &p_source_file, const String &p
 	EditorProgress progress("import", TTR("Import Scene"), 104);
 	progress.step(TTR("Importing Scene..."), 0);
 
-	for (Set<Ref<EditorSceneFormatImporter>>::Element *E = importers.front(); E; E = E->next()) {
+	for (Ref<EditorSceneFormatImporter> importer_elem : importers) {
 		List<String> extensions;
-		E->get()->get_extensions(&extensions);
+		importer_elem->get_extensions(&extensions);
 
 		for (const String &F : extensions) {
 			if (F.to_lower() == ext) {
-				importer = E->get();
+				importer = importer_elem;
 				break;
 			}
 		}
@@ -2086,6 +2086,24 @@ ResourceImporterScene::ResourceImporterScene() {
 	singleton = this;
 }
 
+void ResourceImporterScene::add_importer(Ref<EditorSceneFormatImporter> p_importer) {
+	ERR_FAIL_COND(p_importer.is_null());
+	importers.insert(0, p_importer);
+}
+
+void ResourceImporterScene::remove_post_importer_plugin(const Ref<EditorScenePostImportPlugin> &p_plugin) {
+	post_importer_plugins.erase(p_plugin);
+}
+
+void ResourceImporterScene::add_post_importer_plugin(const Ref<EditorScenePostImportPlugin> &p_plugin) {
+	ERR_FAIL_COND(p_plugin.is_null());
+	post_importer_plugins.insert(0, p_plugin);
+}
+
+void ResourceImporterScene::remove_importer(Ref<EditorSceneFormatImporter> p_importer) {
+	importers.erase(p_importer);
+}
+
 ///////////////////////////////////////
 
 uint32_t EditorSceneFormatImporterESCN::get_import_flags() const {

editor/import/resource_importer_scene.h

@@ -153,7 +153,7 @@ VARIANT_ENUM_CAST(EditorScenePostImportPlugin::InternalImportCategory)
 class ResourceImporterScene : public ResourceImporter {
 	GDCLASS(ResourceImporterScene, ResourceImporter);
 
-	Set<Ref<EditorSceneFormatImporter>> importers;
+	Vector<Ref<EditorSceneFormatImporter>> importers;
 
 	static ResourceImporterScene *singleton;
 
@@ -224,13 +224,13 @@ class ResourceImporterScene : public ResourceImporter {
 public:
 	static ResourceImporterScene *get_singleton() { return singleton; }
 
-	void add_post_importer_plugin(const Ref<EditorScenePostImportPlugin> &p_plugin) { post_importer_plugins.push_back(p_plugin); }
-	void remove_post_importer_plugin(const Ref<EditorScenePostImportPlugin> &p_plugin) { post_importer_plugins.erase(p_plugin); }
+	void add_post_importer_plugin(const Ref<EditorScenePostImportPlugin> &p_plugin);
+	void remove_post_importer_plugin(const Ref<EditorScenePostImportPlugin> &p_plugin);
 
-	const Set<Ref<EditorSceneFormatImporter>> &get_importers() const { return importers; }
+	const Vector<Ref<EditorSceneFormatImporter>> &get_importers() const { return importers; }
 
-	void add_importer(Ref<EditorSceneFormatImporter> p_importer) { importers.insert(p_importer); }
-	void remove_importer(Ref<EditorSceneFormatImporter> p_importer) { importers.erase(p_importer); }
+	void add_importer(Ref<EditorSceneFormatImporter> p_importer);
+	void remove_importer(Ref<EditorSceneFormatImporter> p_importer);
 
 	virtual String get_importer_name() const override;
 	virtual String get_visible_name() const override;