Ensure correct unlocking of script editor history

Author: HolonProduction

doc/classes/Object.xml

@@ -476,6 +476,7 @@
 				node.CallDeferred(Node3D.MethodName.Rotate, new Vector3(1f, 0f, 0f), 1.571f);
 				[/csharp]
 				[/codeblocks]
+				For methods which are deferred from the same thread, the order of execution at idle time is identical to the order in which [code skip-lint]call_deferred[/code] was called.
 				See also [method Callable.call_deferred].
 				[b]Note:[/b] In C#, [param method] must be in snake_case when referring to built-in Godot methods. Prefer using the names exposed in the [code]MethodName[/code] class to avoid allocating a new [StringName] on each call.
 				[b]Note:[/b] If you're looking to delay the function call by a frame, refer to the [signal SceneTree.process_frame] and [signal SceneTree.physics_frame] signals.

editor/script/script_editor_plugin.cpp

@@ -676,7 +676,6 @@ void ScriptEditor::_save_history() {
 void ScriptEditor::_save_previous_state(Dictionary p_state) {
 	if (lock_history) {
 		// Done as a result of a deferred call triggered by set_edit_state().
-		lock_history = false;
 		return;
 	}
 
@@ -3853,6 +3852,10 @@ void ScriptEditor::_update_selected_editor_menu() {
 	}
 }
 
+void ScriptEditor::_unlock_history() {
+	lock_history = false;
+}
+
 void ScriptEditor::_update_history_pos(int p_new_pos) {
 	Node *n = tab_container->get_current_tab_control();
 
@@ -3872,6 +3875,10 @@ void ScriptEditor::_update_history_pos(int p_new_pos) {
 	if (seb) {
 		lock_history = true;
 		seb->set_edit_state(history[history_pos].state);
+		// `set_edit_state()` can modify the caret position which might trigger a
+		// request to save the history. Since `TextEdit::caret_changed` is emitted
+		// deferred, we need to defer unlocking of the history as well.
+		callable_mp(this, &ScriptEditor::_unlock_history).call_deferred();
 		seb->ensure_focus();
 
 		Ref<Script> scr = seb->get_edited_resource();

editor/script/script_editor_plugin.h

@@ -526,6 +526,7 @@ class ScriptEditor : public PanelContainer {
 
 	bool waiting_update_names;
 	bool lock_history = false;
+	void _unlock_history();
 
 	void _help_class_open(const String &p_class);
 	void _help_class_goto(const String &p_desc);