Godot: Using the Inspector to create a New Script tries to inherit from the wrong class

[KellyThomas]

Godot version:
v3.1.1.stable.mono.official
v3.2.dev.mono.custom_build.ad0d87b4d

OS/device including version:
Windows 10

Issue description:
When I use the inspector to replace an attached script with a new script it defaults to inheriting from the script I am replacing.

At the moment this clearly wrong - I am replacing a GDScript script with a C# script so inheritance is impossible. However even if I wasn't switching languages I'm not sure this would be the common workflow.

If instead I Clear the script first before selecting New Script then the dialog offers to inherit from the correct node type.

Steps to reproduce:
Use the Inspector to select New Script on a node that already has one:

Note the value in the Inherits field:

[akien-mga]

The behaviour of inheriting the existing script is a good feature, but it should be moved to an Extend Script menu option, like there is where you right-click on a node with an existing script.

So it should be:

• New Script
• Extend Script
  when there is an existing script, and:
• New Script
  otherwise.

"Extend Script" should ensure that the "Language" field matches the one of the script being inherited.

[cgxeiji]

Hi, I wanted to take a look at this issue. Adding the following:

case OBJ_MENU_NEW_SCRIPT: {

    if (Object::cast_to<Node>(get_edited_object())) {
        Node *n = Object::cast_to<Node>(get_edited_object());
        Ref<Script> empty = EditorNode::get_singleton()->get_object_custom_type_base(n);
        n->set_script(empty.get_ref_ptr());
        EditorNode::get_singleton()->get_scene_tree_dock()->open_script_dialog(n);
    }

} break;
case OBJ_MENU_EXTEND_SCRIPT: {

    if (Object::cast_to<Node>(get_edited_object())) {
        EditorNode::get_singleton()->get_scene_tree_dock()->open_script_dialog(Object::cast_to<Node>(get_edited_object()));
    }

} break;

to:
https://github.com/godotengine/godot/blob/1481d299ea97fa1311a75a9ee39eb97d624a8619/editor/editor_properties.cpp#L2184-L2190
seems to behave like expected, but the current script gets removed from the property as soon as New Script is selected (so pressing cancel in the popup does not recover the previous script).

Is there a way to call open_script_dialog() with a no inheritance parameter? Or is it necessary to add a flag somewhere around here?:
https://github.com/godotengine/godot/blob/06a6507751f5899a590a1c67915890550e5a2793/editor/scene_tree_dock.cpp#L432-L446

I apologize if this is a silly solution, it is my first time dwelling this deep into Godot.

[argentite]

Hi, I want to work on this.

Should I add a new case with a name something like TOOL_ATTACH_SCRIPT_SCRATCH to SceneTreeDock::_tool_selected or should I rename the existing TOOL_ATTACH_SCRIPT to TOOL_EXTEND_SCRIPT and add another TOOL_ATTACH_SCRIPT? While the first option is safer the second option seems more sensible.

[akien-mga]

Fixed by #32954.