Add option for LSP diagnostics on change.

Fixes godotengine#87410.

Currently the LSP sends diagnostics on every change.
This means that if you're typing `var thread := Thread.new()`,
the language server sends a diagnostic after every keypress:

```
"Expected variable name after \"var\"."
"Expected variable name after \"var\"."
"(UNUSED_VARIABLE): The local variable \"t\" is declared but never used in the block. If this is intended
"(UNUSED_VARIABLE): The local variable \"th\" is declared but never used in the block. If this is intended
"(UNUSED_VARIABLE): The local variable \"thr\" is declared but never used in the block. If this is intended
"(UNUSED_VARIABLE): The local variable \"thre\" is declared but never used in the block. If this is intended
"(UNUSED_VARIABLE): The local variable \"threa\" is declared but never used in the block. If this is intended
"(UNUSED_VARIABLE): The local variable \"thread\" is declared but never used in the block. If this is intended
"(UNUSED_VARIABLE): The local variable \"thread\" is declared but never used in the block. If this is intended
"Expected type after \":\""
"Expected expression for variable initial value after \"=\"."
"Expected expression for variable initial value after \"=\"."
```

This causes the LSP to be slow and the diagnositcs aren't that helpful.

This patch adds a "Diagnostics on Change" option, which defaults on to maintain existing behavior.
When toggled off, diagnostics are only sent on open/save, and not on every change.

modules/gdscript/language_server/gdscript_language_server.cpp

@@ -44,6 +44,7 @@ GDScriptLanguageServer::GDScriptLanguageServer() {
 	_EDITOR_DEF("network/language_server/enable_smart_resolve", true);
 	_EDITOR_DEF("network/language_server/show_native_symbols_in_editor", false);
 	_EDITOR_DEF("network/language_server/use_thread", use_thread);
+	_EDITOR_DEF("network/language_server/diagnostics_on_change", true);
 }
 
 void GDScriptLanguageServer::_notification(int p_what) {

modules/gdscript/language_server/gdscript_text_document.cpp

@@ -65,7 +65,7 @@ void GDScriptTextDocument::_bind_methods() {
 
 void GDScriptTextDocument::didOpen(const Variant &p_param) {
 	lsp::TextDocumentItem doc = load_document_item(p_param);
-	sync_script_content(doc.uri, doc.text);
+	sync_script_content(doc.uri, doc.text, true);
 }
 
 void GDScriptTextDocument::didClose(const Variant &p_param) {
@@ -82,7 +82,9 @@ void GDScriptTextDocument::didChange(const Variant &p_param) {
 		evt.load(contentChanges[i]);
 		doc.text = evt.text;
 	}
-	sync_script_content(doc.uri, doc.text);
+
+	bool diagnostics_on_save = _EDITOR_GET("network/language_server/diagnostics_on_change");
+	sync_script_content(doc.uri, doc.text, diagnostics_on_save);
 }
 
 void GDScriptTextDocument::willSaveWaitUntil(const Variant &p_param) {
@@ -100,7 +102,7 @@ void GDScriptTextDocument::didSave(const Variant &p_param) {
 	Dictionary dict = p_param;
 	String text = dict["text"];
 
-	sync_script_content(doc.uri, text);
+	sync_script_content(doc.uri, text, true);
 
 	String path = GDScriptLanguageProtocol::get_singleton()->get_workspace()->get_file_path(doc.uri);
 	Ref<GDScript> scr = ResourceLoader::load(path);
@@ -482,9 +484,9 @@ GDScriptTextDocument::GDScriptTextDocument() {
 	file_checker = FileAccess::create(FileAccess::ACCESS_RESOURCES);
 }
 
-void GDScriptTextDocument::sync_script_content(const String &p_path, const String &p_content) {
+void GDScriptTextDocument::sync_script_content(const String &p_path, const String &p_content, bool p_publish_diagnostics) {
 	String path = GDScriptLanguageProtocol::get_singleton()->get_workspace()->get_file_path(p_path);
-	GDScriptLanguageProtocol::get_singleton()->get_workspace()->parse_script(path, p_content);
+	GDScriptLanguageProtocol::get_singleton()->get_workspace()->parse_script(path, p_content, p_publish_diagnostics);
 
 	EditorFileSystem::get_singleton()->update_file(path);
 }

modules/gdscript/language_server/gdscript_text_document.h

@@ -49,7 +49,7 @@ class GDScriptTextDocument : public RefCounted {
 	void willSaveWaitUntil(const Variant &p_param);
 	void didSave(const Variant &p_param);
 
-	void sync_script_content(const String &p_path, const String &p_content);
+	void sync_script_content(const String &p_path, const String &p_content, bool p_publish_diagnostics);
 	void show_native_symbol_in_editor(const String &p_symbol_id);
 
 	Array native_member_completions;

modules/gdscript/language_server/gdscript_workspace.cpp

@@ -112,7 +112,7 @@ void GDScriptWorkspace::did_delete_files(const Dictionary &p_params) {
 		Dictionary file = files[i];
 		String uri = file["uri"];
 		String path = get_file_path(uri);
-		parse_script(path, "");
+		parse_script(path, "", true);
 	}
 }
 
@@ -217,7 +217,7 @@ void GDScriptWorkspace::reload_all_workspace_scripts() {
 		Error err;
 		String content = FileAccess::get_file_as_string(path, &err);
 		ERR_CONTINUE(err != OK);
-		err = parse_script(path, content);
+		err = parse_script(path, content, true);
 
 		if (err != OK) {
 			HashMap<String, ExtendGDScriptParser *>::Iterator S = parse_results.find(path);
@@ -413,7 +413,7 @@ Error GDScriptWorkspace::initialize() {
 	return OK;
 }
 
-Error GDScriptWorkspace::parse_script(const String &p_path, const String &p_content) {
+Error GDScriptWorkspace::parse_script(const String &p_path, const String &p_content, bool p_publish_diagnostics) {
 	ExtendGDScriptParser *parser = memnew(ExtendGDScriptParser);
 	Error err = parser->parse(p_content, p_path);
 	HashMap<String, ExtendGDScriptParser *>::Iterator last_parser = parse_results.find(p_path);
@@ -431,7 +431,9 @@ Error GDScriptWorkspace::parse_script(const String &p_path, const String &p_cont
 		parse_results[p_path] = parser;
 	}
 
-	publish_diagnostics(p_path);
+	if (p_publish_diagnostics) {
+		publish_diagnostics(p_path);
+	}
 
 	return err;
 }
@@ -546,7 +548,7 @@ Error GDScriptWorkspace::parse_local_script(const String &p_path) {
 	Error err;
 	String content = FileAccess::get_file_as_string(p_path, &err);
 	if (err == OK) {
-		err = parse_script(p_path, content);
+		err = parse_script(p_path, content, true);
 	}
 	return err;
 }

modules/gdscript/language_server/gdscript_workspace.h

@@ -76,7 +76,7 @@ class GDScriptWorkspace : public RefCounted {
 public:
 	Error initialize();
 
-	Error parse_script(const String &p_path, const String &p_content);
+	Error parse_script(const String &p_path, const String &p_content, bool p_publish_diagnostics);
 	Error parse_local_script(const String &p_path);
 
 	String get_file_path(const String &p_uri) const;