AnimationPlayer.play_backwards() calls keyframe methods twice

[paulmiller]

Tested versions

reproduced in 4.2.1.stable
not reproduced in 3.5.3.stable, 4.0.4.stable, 4.1.3.stable

System information

Godot v4.2.1.stable unknown - Arch Linux #1 SMP PREEMPT_DYNAMIC Fri, 05 Jan 2024 16:20:41 +0000 - Tty - Vulkan (Forward+) - dedicated NVIDIA GeForce GTX 1070 (nvidia; 545.29.06) - Intel(R) Core(TM) i7-6700 CPU @ 3.40GHz (8 Threads)

Issue description

Animations with "Call Method" tracks work normally when playing forward, but when playing backwards, a single method keyframe results in 2 method calls.

Steps to reproduce

Run the attached project. The buttons in the top left call play() and play_backwards():

func hello():
  print("hello")

func play():
  print("play")
  $AnimationPlayer.play("blah")

func play_backwards():
  print("play_backwards")
  $AnimationPlayer.play_backwards("blah")

The "blah" animation spins the sprite and calls hello() once. When playing forward, Godot prints:

play
hello

But backwards:

play_backwards
hello
hello

Minimal reproduction project (MRP)

animation-callback-test.zip

[TokageItLab]

Dupe of #86147, Already fixed by #86227 in 4.2.2.