Godot: SceneTree.call_group() is doing a deferred call

[kubecz3k]

Godot version:
40d1b0b

OS/device including version:
Ubuntu 18.04 64bit

Issue description:
Using SceneTree.call_group() will perform in-explicitly a deferred call. This behavior is not described in any documentation and can lead to potential function misuse.
I'm not sure but I assume it should be changed to just perform call normally for consistency (the same way how we have node.call() and node.call_deferred() functions, we would have SceneTree.call_group() and SceneTree.call_group_flags()).

Worth to notice this change could potentially break compatibility.

Steps to reproduce:
Manual:

1. Create scene called GroupCallReceiver
2. Add root node of GroupCallReceiver to "GroupCallReceiver" group
3. Add func some_function(): print("performing GroupCallReceiver function") inside
4. Create scene called CallGroupIssue, instance GroupCallReceiver inside
5. Add such implementation of ready to CallGroupIssue

func _ready():
    get_tree().call_group("GroupCallReceiver", "some_function")
    print("After doing a call_group()")

1. Run CallGroupIssue scene and see in the output the "After doing a call_group()" string is printed before "performing GroupCallReceiver function"

Automatic:

1. Download reproduction project
2. Open it
3. Start with F5
4. See in the output the "After doing a call_group()" string is printed before "performing GroupCallReceiver function" (related scenes: IssueCallGroup.tscn and GroupCallReceiver.tscn)

Minimal reproduction project:
call_group_deferred.zip

[leodimano]

Hello @kubecz3k this is not a bug, indeed call_group is by default executed on an idle/deferred time. For realtime group call you should use the method "call_group_flags" and use the GROUP_CALL_REALTIME enumerator.

Scene Tree/Call Group Flags

[Calinou]

It might be worth changing this in 4.0 for consistency, but I wonder why it's deferred by default in the first place.