Unable to use AnimatedStreamLines : Scene-caching Bug (circular reference)

[Aathish04]

Consider the following test script, slightly shortened from one of Grant's older videos:

from manim import *

class TestVectorField(Scene):
    def four_swirls_function(self,point):
        x, y = point[:2]
        result = ((y**3 - 4 * y) * RIGHT + (x**3 - 16 * x) * UP)*0.05
        return result

    def construct(self):
        lines = StreamLines(self.four_swirls_function)
        self.add(AnimatedStreamLines(
            lines,
            line_anim_class=ShowPassingFlash
        ))
        self.wait(2)

The scene above fails in the latest version of Manim in the master branch, and the traceback is as follows:

Traceback (most recent call last):
  File "/Users/aathishs/Python/ManimEnv/manim/manim/__main__.py", line 168, in main
    scene = SceneClass()
  File "/Users/aathishs/Python/ManimEnv/manim/manim/scene/scene.py", line 73, in __init__
    self.construct()
  File "/Users/aathishs/Python/ManimEnv/projects/TestAnimatedStreamLines.py", line 15, in construct
    self.wait(2)
  File "/Users/aathishs/Python/ManimEnv/manim/manim/scene/scene.py", line 900, in wrapper
    hash_wait = get_hash_from_wait_call(
  File "/Users/aathishs/Python/ManimEnv/manim/manim/utils/hashing.py", line 175, in get_hash_from_wait_call
    current_mobjects_list_json = [
  File "/Users/aathishs/Python/ManimEnv/manim/manim/utils/hashing.py", line 176, in <listcomp>
    get_json(x) for x in sorted(current_mobjects_list, key=lambda obj: str(obj))
  File "/Users/aathishs/Python/ManimEnv/manim/manim/utils/hashing.py", line 98, in get_json
    return json.dumps(obj, cls=CustomEncoder)
  File "/usr/local/Cellar/python@3.8/3.8.5/Frameworks/Python.framework/Versions/3.8/lib/python3.8/json/__init__.py", line 234, in dumps
    return cls(
  File "/Users/aathishs/Python/ManimEnv/manim/manim/utils/hashing.py", line 82, in encode
    return super().encode(self._encode_dict(obj))
  File "/usr/local/Cellar/python@3.8/3.8.5/Frameworks/Python.framework/Versions/3.8/lib/python3.8/json/encoder.py", line 199, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "/usr/local/Cellar/python@3.8/3.8.5/Frameworks/Python.framework/Versions/3.8/lib/python3.8/json/encoder.py", line 257, in iterencode
    return _iterencode(o, 0)
ValueError: Circular reference detected

I believe this is a Scene Caching bug, as the traceback points to the sections where Scene Caching was implemented.
Further confirming this is the fact that commit 9584dfe, the last commit before Scene Caching was merged, renders the scene just fine, but the commit after scene caching was merged fails with the exact same error.

Mentioning @huguesdevimeux since he PR'd Scene Caching.

[huguesdevimeux]

Thank you for the report!

This is definitely a Scene Caching error. I will try to find a fix.

[kolibril13]

from manim import *

class ExampleScene(Scene):
    def get_dot(self,num):
        return Dot().shift(LEFT*0.01 *num)
    def construct(self):
        tick_start=0
        tick_end=100
        val_tracker= ValueTracker(tick_start)
        dot= self.get_dot(val_tracker.get_value())
        dot.add_updater(lambda x: x.become(self.get_dot(val_tracker.get_value())))
        self.add(dot)
        self.play(val_tracker.set_value, tick_end, rate_func= linear)
        self.wait()

gives me "ValueError: Circular reference detected"
However, when I run it with the flag "--disable_caching" it is rendering properly