PopupPanel _ready() not called, "error calling method from signal" upon opening

[mitchcurtis]

Godot version:

3.1

OS/device including version:

macOS 10.14.6
MacBook Pro

Issue description:

1. _ready() is not called at all. From the tests I did with a super minimal example, it should be called after _init() -- without having to open the popup.
2. When opening the popup, I get this error message:

E 0:00:01:0485   Error calling method from signal 'about_to_show': 'PopupPanel::on_about_to_show': Method not found.
  <C Source>     core/object.cpp:1238 @ emit_signal()
  <Stack Trace>  MainScene.gd:9 @ _unhandled_input()

I was not able to reproduce either of these issues starting from scratch with a minimal example, only when reducing my existing project down to the attached version.

Steps to reproduce:
Run the attached project and press T to open the popup.

Minimal reproduction project:
popup-test.zip

[mitchcurtis]

OK, I figured out a workaround for #1: attach the SavePopup.gd script to the instance of SavePopup. This shouldn't be necessary, since SavePopup.tscn already has a script attached to its root node.

I'm not sure how the script managed to get removed, as every time I add an instance now, while testing, it has a script attached. Still, should it matter? Shouldn't instances of a .tscn use the script attached to the root node of that .tscn?

[akien-mga]

Your instance had script removed, which does not happen when creating new instances (either via drag and drop or by pressing the "Instance" button):

So most likely you reset the script yourself somehow, e.g. by pressing the "Clear Script" button on the instance.

If you can reproduce a scenario where the script is lost without you removing it, then please file a dedicated bug report.