Fix CONNECT_APPEND_SOURCE_OBJECT to bind on signal emission

[kleonc]

Fixes #114326.

Changes CONNECT_APPEND_SOURCE_OBJECT to bind the source object on signal emission. Previously it was done only on PackedScene instantiation, which led to bugs/inconsistencies.

• CONNECT_APPEND_SOURCE_OBJECT did not work on runtime connections.
• On runtime, duplicating a Node with the source object/Node binded during the scene instantiation would not replace the binded source object with the newly duplicated one.
• The source object/Node binded during the scene instantiation might be tried to be saved in the scene file.
• etc.

Modified MRP from #114326 with the examples below: duplicate-signal-extra-arg_v2.zip

Before (v4.6.beta2.official [551ce8d])	After (this PR)

Relevant part of control.tscn from #114326 MRP:

• Before (v4.6.beta2.official [551ce8d]):

[connection signal="resized" from="Parent/Child" to="Parent" method="_on_child_resized" flags=18]
[connection signal="resized" from="Parent2/Child" to="Parent2" method="_on_child_resized" flags=18 binds= [Object(Control,"unique_name_in_owner":false,"process_mode":0,"process_priority":0,"process_physics_priority":0,"process_thread_group":0,"physics_interpolation_mode":2,"auto_translate_mode":0,"editor_description":"","visible":true,"modulate":Color(1, 1, 1, 1),"self_modulate":Color(1, 1, 1, 1),"show_behind_parent":false,"top_level":false,"clip_children":0,"light_mask":1,"visibility_layer":1,"z_index":0,"z_as_relative":true,"y_sort_enabled":false,"texture_filter":0,"texture_repeat":0,"material":null,"use_parent_material":false,"clip_contents":false,"custom_minimum_size":Vector2(0, 0),"layout_direction":0,"layout_mode":0,"anchors_preset":0,"anchor_left":0.0,"anchor_top":0.0,"anchor_right":0.0,"anchor_bottom":0.0,"offset_left":0.0,"offset_top":0.0,"offset_right":40.0,"offset_bottom":40.0,"grow_horizontal":1,"grow_vertical":1,"rotation":0.0,"scale":Vector2(1, 1),"pivot_offset":Vector2(0, 0),"pivot_offset_ratio":Vector2(0, 0),"size_flags_horizontal":1,"size_flags_vertical":1,"size_flags_stretch_ratio":1.0,"localize_numeral_system":true,"tooltip_text":"","tooltip_auto_translate_mode":0,"focus_neighbor_left":NodePath(""),"focus_neighbor_top":NodePath(""),"focus_neighbor_right":NodePath(""),"focus_neighbor_bottom":NodePath(""),"focus_next":NodePath(""),"focus_previous":NodePath(""),"focus_mode":0,"focus_behavior_recursive":0,"mouse_filter":0,"mouse_behavior_recursive":0,"mouse_force_pass_scroll_events":true,"mouse_default_cursor_shape":0,"shortcut_context":null,"accessibility_name":"","accessibility_description":"","accessibility_live":0,"accessibility_controls_nodes":Array[NodePath]([]),"accessibility_described_by_nodes":Array[NodePath]([]),"accessibility_labeled_by_nodes":Array[NodePath]([]),"accessibility_flow_to_nodes":Array[NodePath]([]),"theme":null,"theme_type_variation":&"","script":null)
]]

• After (this PR):

[connection signal="resized" from="Parent/Child" to="Parent" method="_on_child_resized" flags=18]
[connection signal="resized" from="Parent2/Child" to="Parent2" method="_on_child_resized" flags=18]

[kleonc]

cc @Rindbee (#60143)

[Rindbee]

Looks good to me!

[kleonc]

I've realized this is not a proper fix, this would break for a runtime duplication of a Node with source binded using CONNECT_APPEND_SOURCE_OBJECT (which is broken even before this PR as binds including the source Node would be duplicated but without retargetting the binded source to be relative to the duplicated-new-node if possible).

CONNECT_APPEND_SOURCE_OBJECT seems to be broken / half-baked in general, as e.g. connecting to a signal with CONNECT_APPEND_SOURCE_OBJECT flag does not bind the source on runtime, only when saving to a PackedScene. This leads to bugs/inconsistencies.

@tool
extends EditorScript

class Signaler:
	signal sig

class Receiver:
	func callback(source: Object) -> void:
		print("%s.callback( source=%s )" % [self, source])

func _run() -> void:
	var source := Signaler.new()
	var receiver := Receiver.new()

	source.sig.connect(receiver.callback, CONNECT_APPEND_SOURCE_OBJECT)
	source.sig.emit() # ERROR: core/object/object.cpp:1310 - Error calling from signal 'sig' to callable: 'RefCounted::callback': Method expected 1 argument(s), but called with 0.

[Rindbee]

CONNECT_APPEND_SOURCE_OBJECT seems to be broken / half-baked in general, as e.g. connecting to a signal with CONNECT_APPEND_SOURCE_OBJECT flag does not bind the source on runtime, only when saving to a PackedScene.

CONNECT_APPEND_SOURCE_OBJECT is currently a flag primarily used for PackedScene and is somewhat redundant now. It was originally intended to enhance the functionality of the connection dialog, but the ability to add extra parameters of type NodePath (^".") now effectively replaces this functionality.

[kleonc]

CONNECT_APPEND_SOURCE_OBJECT is currently a flag primarily used for PackedScene and is somewhat redundant now. It was originally intended to enhance the functionality of the connection dialog, but the ability to add extra parameters of type NodePath (^".") now effectively replaces this functionality.

I've moved handling CONNECT_APPEND_SOURCE_OBJECT to Object / removed special handling from PackedScene. PR description updated.

[Rindbee]

Using bind() again (like a Russian nesting doll) will cancel the source's emission (not the original arguments) if unbinding is enabled (unbind > 0).