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MLP227: always_update_mobjects forces a provably static wait

qual reports MLP227 on a wait made dynamic only by a literal always_update_mobjects = True while the wait's interval provably has nothing to update: no scene updater, no stop condition, no camera motion (the scene commits to the plain 2D Scene camera), and no registered mobject updater of any arity. Every frame then runs the full frame pipeline — family walk, update pass, re-render — to reproduce an identical image (DESIGN 3.3, 7.3).

  • Default severity: warning
  • Minimum confidence: high — a Maybe flag value (any non-literal write) never fires
  • Implementation phase: 3
  • Fix: none

The static proof deliberately requires no updaters at all, not just no time-based ones: without the flag, a wait whose family holds only one-argument updaters freezes and those updaters stop running (DESIGN 3.3), so suggesting the flag's removal is only visual-preserving when nothing updates. Unknown-kind objects and intrinsically per-frame classes (such as TracedPath) also void the proof. Freezing does not shorten the video — the encoder still writes the full wait duration.

Wrong

class Demo(Scene):
    def construct(self):
        self.always_update_mobjects = True
        square = Square()
        self.add(square)
        self.wait(3)          # ~180 identical frames, full pipeline each

class Demo(Scene):
    def construct(self):
        square = Square()
        self.add(square)
        self.wait(3)          # frozen wait