Improved handling of attributes when using the .animate syntax (#2665)

* apply all methods to original mobject after finishing _MethodBuilder animation

* added test to check whether custom attributes are changed

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: behackl

manim/animation/transform.py

@@ -360,6 +360,11 @@ def __init__(self, mobject, methods):
         self.methods = methods
         super().__init__(mobject)
 
+    def finish(self) -> None:
+        for method, method_args, method_kwargs in self.methods:
+            method.__func__(self.mobject, *method_args, **method_kwargs)
+        super().finish()
+
 
 class ApplyMethod(Transform):
     """Animates a mobject by applying a method.

manim/mobject/mobject.py

@@ -2783,7 +2783,6 @@ def __call__(self, **kwargs):
 
     def __getattr__(self, method_name):
         method = getattr(self.mobject.target, method_name)
-        self.methods.append(method)
         has_overridden_animation = hasattr(method, "_override_animate")
 
         if (self.is_chaining and has_overridden_animation) or self.overridden_animation:
@@ -2801,6 +2800,7 @@ def update_target(*method_args, **method_kwargs):
                     **method_kwargs,
                 )
             else:
+                self.methods.append([method, method_args, method_kwargs])
                 method(*method_args, **method_kwargs)
             return self
 

tests/test_scene_rendering/test_play_logic.py

@@ -101,3 +101,19 @@ def test_t_values_save_last_frame(using_temp_config):
     scene.update_to_time = Mock()
     scene.render()
     scene.update_to_time.assert_called_once_with(1)
+
+
+def test_animate_with_changed_custom_attribute(using_temp_config):
+    """Test that animating the change of a custom attribute
+    using the animate syntax works correctly.
+    """
+
+    class CustomAnimateScene(Scene):
+        def construct(self):
+            vt = ValueTracker(0)
+            vt.custom_attribute = "hello"
+            self.play(vt.animate.set_value(42).set(custom_attribute="world"))
+            assert vt.get_value() == 42
+            assert vt.custom_attribute == "world"
+
+    CustomAnimateScene().render()