Collision hand grab-regrab race condition

[Ritter7124]

in grab.gd

func release() -> void:
	# Clear any hand pose
	_clear_hand_pose()

	# Remove collision exceptions with a small delay
	if is_instance_valid(collision_hand) and not _collision_exceptions.is_empty():
		# Use RIDs instead of the objects directly in case they get freed while
		# we are waiting for the object to fall away
		var copy : Array[RID] = _collision_exceptions.duplicate()
		_collision_exceptions.clear()

		# Delay removing our exceptions to give the object time to fall away
		collision_hand.get_tree().create_timer(0.5).timeout \    #<------------------
			.connect(_remove_collision_exceptions \
				.bind(copy) \
				.bind(collision_hand.get_rid()))

	# Report the release
	print_verbose("%s> released by %s", [what.name, by.name])
	what.released.emit(what, by)

there is a timer that calls a static function of grab.gd after a half second timer which then deletes the copy of exceptions we pass it through, and there is a comment on this static function that has an idea about restarting the timer if we still have collisions with OTHER objects. But there is a nasty problem if the player drops and regrabs the same object within this .5 interval. Colliding with a grabbed object is very bad as a whole sleuth of stuff can happen depending on your vr setup. For me it was causing my hand to fly away and break a leash radius and drop the object, which is very tough ahaha. Anyway here is my fix, I didn't want to create a pull request because my version is very behind and I didn't want to clone a fresh project and do all of that, since I'm not sure my solution is the best one. Anyways here is what I cooked up.

func release() -> void:
	# Clear any hand pose
	_clear_hand_pose()

	# Remove collision exceptions with a small delay
	if is_instance_valid(collision_hand) and not _collision_exceptions.is_empty():
		# We need to make a copy of our array else it will be passed by reference.
		var copy : Array[PhysicsBody3D]
		for exc in _collision_exceptions:
			copy.push_back(exc)
		_collision_exceptions.clear()
		print(collision_hand, " in grab.gd!!")
		
		collision_hand.remove_collision_exceptions_delay(copy, what)

	# Report the release
	print_verbose("%s> released by %s", [what.name, by.name])
	what.released.emit(what, by)

then in collision_hand.gd

const DELAY_DURATION: float = .5
func remove_collision_exceptions_delay(
	collision_exceptions: Array[PhysicsBody3D], 
 	picakble: XRToolsPickable):
		
	await get_tree().create_timer(DELAY_DURATION).timeout
	if (!is_instance_valid(self)):
		return  #we don't exist so who cares
		
	if (is_instance_valid(picakble) and picakble.is_picked_up()):
		collision_exceptions.remove_at(collision_exceptions.find(picakble))

		
	for body: PhysicsBody3D in collision_exceptions:
		if (is_instance_valid(body)):
			self.remove_collision_exception_with(body)
			body.remove_collision_exception_with(self)

I figured if anything should deal with the exceptions it should be the hand, and if we had a problem with the single object just pass it to before the grab.gd is destroyed. I see some warnings that collisionhand is deprecated anyways? But I didn't see another solution and it works great besides this one little issue I had with it. Anyways cheers for reading through this and have a good one!

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