Add _after_ready() to ensure that logic runs when all nodes in scenetree are ready

[azur-wolve]

Godot aims for intuitiveness and usability.

One of the problems that newcomers always face is the initialization order of nodes regarding READY.
It has been said to be found counter-intuitive multiple times.
(as for the rest of the tree creation, the steps go from up hierarchy to down. Is the ready step that only goes from down to up)

The children come first as its expected that nodes higher in the tree hierarchy use nodes that are lower and not vice-versa, which is a good practice.

However there are cases where is needed to check something on an ancestor from a descendant.

Currently _ready() is the last "step" before the first game loop iteration

if there were an _after_ready() could solve some of that, so its ensured that all nodes have been initialized and are ready with _init() and _ready() respectively.

Also its handy as we move nodes around the hierarchy when trying new things on scene prototyping stages, so we don't have to worry where they are moved to, and change the code every time, or being limited to avoid changing it.
All that regarding to the initialization step when launching a scene.

Right now to have such behavior would need something like:

func _ready():
    # some ready stuff
    _after_ready.call_deferred()

func _after_ready():
    # whatever

Maybe that could throw some problem even?

[sockeye-d]

If you need to wait for a parent to be ready, you can do

await get_parent().ready

Or if you need to wait for the whole tree to be ready:

await get_tree().root.ready

I think this is a nice idea but it's really easy to work around it

[azur-wolve]

what idk is if its recommendable to populate the stack with multiple awaits
maybe someone can clarify

[OffsetMOSFET]

It's an await that happens once during setup. It should be fine.

Also, to add to sockeye-d's example, if you can't guarantee a node's load order (sibling/cousin node), I recommend just checking is_node_ready() first, otherwise you might be awaiting after the ready signal has fired.

[keyzeuh]

I made a pull request about this: godotengine/godot#108413

[dalexeev]

Next time someone asks for _after_after_ready()? I think it's redundant. We already have _enter_tree() which is called from parent to child and _ready() which is called from child to parent. The fact that you need an additional callback probably indicates a problem with the architecture of your project and a violation of the intended relationship between parent and child nodes ("signal up, method down").