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MLC115: Scene.remove(child) undone by re-adding the surviving parent

qual reports MLC115 when Scene.remove(child) removes a child whose parent group keeps it in submobjects, and that parent later definitely returns to the scene (an explicit add, or the auto-add of a play). Scene.remove restructures only the scene root list (scene.py restructure_mobjects); the parent's own child list is not edited, so the removed child reappears with the parent.

  • Default severity: warning
  • Minimum confidence: high
  • Implementation phase: 2
  • Fix: none (removing the child from the parent too is suggested)

A structural parent.remove(child) between the removal and the re-add, a removal of the whole parent (no surviving parents), an explicit re-add of the child itself, and branch-dependent re-adds all stay silent.

Wrong

class Demo(Scene):
    def construct(self):
        square, dot = Square(), Dot()
        group = VGroup(square, dot)
        self.add(group)
        self.remove(dot)
        self.play(FadeIn(group))  # dot reappears

class Demo(Scene):
    def construct(self):
        square, dot = Square(), Dot()
        group = VGroup(square, dot)
        self.add(group)
        self.remove(dot)
        group.remove(dot)  # structural removal too
        self.play(FadeIn(group))