Fix memory leak in GDScript during infinnity loops with yields

[jkb0o]

Fixes #19823 introduced in #17291

The code below passes assertions

extends Node

var iterations = 5;

func _ready():
	print("start single_yield()")
	assert(yield(single_yield(), "completed") == 1)
	print("done single_yield()")
	print("start three_yields()")
	assert(yield(three_yields(), "completed") == 3)
	print("done three_yields()")
	var num_objects = Performance.get_monitor(Performance.OBJECT_COUNT) - 2
	while iterations:
		yield(get_tree(), "idle_frame")
		yield(get_tree(), "idle_frame")
		yield(get_tree(), "idle_frame")
		var current_objects = Performance.get_monitor(Performance.OBJECT_COUNT)
		print("yield 3 idle frames, current objects == ", current_objects, ", awaits ", num_objects, " objects")
		assert(num_objects == current_objects)
		iterations -= 1
	
func single_yield():
	var i = 0
	print("  single_yield: -> yield1")
	yield(get_tree(), "idle_frame")
	print("  single_yield: -> yield1 ->")
	i += 1
	return i
	
func three_yields():
	var i = 0
	print(" three_yields: -> yield1")
	yield(get_tree(), "idle_frame")
	
	print(" three_yields: -> yield1 -> yield2")
	i += 1

	yield(get_tree(), "idle_frame")
	
	print(" three_yields: -> yield1 -> yield2 -> yield3")	
	i += 1

	yield(get_tree(), "idle_frame")
	
	i += 1
	print(" three_yields: -> yield1 -> yield2 -> yield3 ->")	
	return i

and produce output

start single_yield()
  single_yield: -> yield1
  single_yield: -> yield1 ->
done single_yield()
start three_yields()
 three_yields: -> yield1
 three_yields: -> yield1 -> yield2
 three_yields: -> yield1 -> yield2 -> yield3
 three_yields: -> yield1 -> yield2 -> yield3 ->
done three_yields()
yield 3 idle frames, current objects == 837, awaits 837 objects
yield 3 idle frames, current objects == 837, awaits 837 objects
yield 3 idle frames, current objects == 837, awaits 837 objects
yield 3 idle frames, current objects == 837, awaits 837 objects
yield 3 idle frames, current objects == 837, awaits 837 objects

Also I'm attaching example project witch fails with 3.0.3+ and passes with current pr.
godot_yield_leak.zip

CC @Warlaan

[akien-mga]

Please don't put condition and code block inline for ifs, it makes it hard to read what is the condition and what is the statement that will be executed. We tolerate it for simple if (cond) return false;, but even then I'd advise not to use it.

[jkb0o]

Ah, makes sense. Fixed.

[puppetmaster-]

this script should be included in the Godot test project 😄

[jkb0o]

It actually is. But it is also here for those lazy and trustful persons like me (=

[akien-mga]

Cherry-picked for 3.0.7.