Bugfix: allow new-style method animation to be used in animation grou…

…ps (#906)

* make sure animations from _AnimationBuilder are built before adding to AnimationGroup

* add test for _AnimationBuilder in group

* black

* delegate building of animation to prepare_animation

* black

* remove unused import

* rewrite loop as list comprehension

Co-authored-by: friedkeenan <friedkeenan@protonmail.com>

Co-authored-by: friedkeenan <friedkeenan@protonmail.com>

manim/animation/animation.py

@@ -5,6 +5,7 @@
 
 
 import typing
+from typing import Union
 from copy import deepcopy
 
 import numpy as np
@@ -13,7 +14,7 @@
     from manim.scene.scene import Scene
 
 from .. import logger
-from ..mobject.mobject import Mobject
+from ..mobject.mobject import Mobject, _AnimationBuilder
 from ..utils.rate_functions import smooth
 
 DEFAULT_ANIMATION_RUN_TIME: float = 1.0
@@ -35,7 +36,7 @@ def __init__(
         name: str = None,
         remover: bool = False,  # remove a mobject from the screen?
         suspend_mobject_updating: bool = True,
-        **kwargs
+        **kwargs,
     ) -> None:
         self._typecheck_input(mobject)
         self.run_time = run_time
@@ -66,7 +67,10 @@ def _typecheck_input(self, mobject: Mobject) -> None:
     def __str__(self) -> str:
         if self.name:
             return self.name
-        return self.__class__.__name__ + str(self.mobject)
+        return f"{self.__class__.__name__}({str(self.mobject)})"
+
+    def __repr__(self) -> str:
+        return str(self)
 
     def begin(self) -> None:
         # This is called right as an animation is being
@@ -191,6 +195,42 @@ def is_remover(self) -> bool:
         return self.remover
 
 
+def prepare_animation(anim: Union["Animation", "_AnimationBuilder"]) -> "Animation":
+    r"""Returns either an unchanged animation, or the animation built
+    from a passed animation factory.
+
+    Examples
+    --------
+
+    ::
+
+        >>> from manim import Square, FadeIn
+        >>> s = Square()
+        >>> prepare_animation(FadeIn(s))
+        FadeIn(Square)
+
+    ::
+
+        >>> prepare_animation(s.animate.scale(2).rotate(42))
+        _MethodAnimation(Square)
+
+    ::
+
+        >>> prepare_animation(42)
+        Traceback (most recent call last):
+        ...
+        TypeError: Object 42 cannot be converted to an animation
+
+    """
+    if isinstance(anim, _AnimationBuilder):
+        return anim.build()
+
+    if isinstance(anim, Animation):
+        return anim
+
+    raise TypeError(f"Object {anim} cannot be converted to an animation")
+
+
 class Wait(Animation):
     def __init__(
         self, duration: float = 1, stop_condition=None, **kwargs

manim/animation/composition.py

@@ -3,7 +3,7 @@
 
 import numpy as np
 
-from ..animation.animation import Animation
+from ..animation.animation import Animation, prepare_animation
 from ..mobject.mobject import Group, Mobject
 from ..scene.scene import Scene
 from ..utils.bezier import interpolate
@@ -29,7 +29,7 @@ def __init__(
         lag_ratio: float = 0,
         **kwargs
     ) -> None:
-        self.animations = animations
+        self.animations = [prepare_animation(anim) for anim in animations]
         self.group = group
         if self.group is None:
             self.group = Group(

manim/scene/scene.py

@@ -16,7 +16,7 @@
 import numpy as np
 
 from .. import config, logger
-from ..animation.animation import Animation, Wait
+from ..animation.animation import Animation, Wait, prepare_animation
 from ..animation.transform import MoveToTarget, _MethodAnimation
 from ..camera.camera import Camera
 from ..constants import *
@@ -618,17 +618,18 @@ def compile_animations(self, *args, **kwargs):
         """
         animations = []
         for arg in args:
-            if isinstance(arg, _AnimationBuilder):
-                animations.append(arg.build())
-            elif isinstance(arg, Animation):
-                animations.append(arg)
-            elif inspect.ismethod(arg):
-                raise TypeError(
-                    "Passing Mobject methods to Scene.play is no longer supported. Use "
-                    "Mobject.animate instead."
-                )
-            else:
-                raise TypeError(f"Unexpected argument {arg} passed to Scene.play().")
+            try:
+                animations.append(prepare_animation(arg))
+            except TypeError:
+                if inspect.ismethod(arg):
+                    raise TypeError(
+                        "Passing Mobject methods to Scene.play is no longer"
+                        " supported. Use Mobject.animate instead."
+                    )
+                else:
+                    raise TypeError(
+                        f"Unexpected argument {arg} passed to Scene.play()."
+                    )
 
         for animation in animations:
             for k, v in kwargs.items():

tests/test_composition.py

@@ -1,8 +1,8 @@
-import pytest
-from manim.animation.composition import Succession
-from manim.animation.fading import FadeInFrom, FadeOutAndShift
+from manim.animation.animation import Animation
+from manim.animation.composition import AnimationGroup, Succession
+from manim.animation.fading import FadeIn, FadeInFrom, FadeOutAndShift
 from manim.constants import DOWN
-from manim.mobject.geometry import Line
+from manim.mobject.geometry import Line, Square, Circle
 
 
 def test_succession_timing():
@@ -76,3 +76,12 @@ def test_succession_in_succession_timing():
     assert succession.active_animation is None
     assert nested_succession.active_index == 2
     assert nested_succession.active_animation is None
+
+
+def test_animationbuilder_in_group():
+    sqr = Square()
+    circ = Circle()
+    animation_group = AnimationGroup(sqr.animate.shift(DOWN).scale(2), FadeIn(circ))
+    assert all(isinstance(anim, Animation) for anim in animation_group.animations)
+    succession = Succession(sqr.animate.shift(DOWN).scale(2), FadeIn(circ))
+    assert all(isinstance(anim, Animation) for anim in succession.animations)