IssueTracker

Reproduction project: https://github.com/lwasyl/compose-animations-playground/tree/ca53b643d1c0d55131b6c6623aa6c06c62a304cc

See the attached video for the observed vs expected behavior. What I believe is a bug is the fact that the green container lags behind the gray one when animating, which I attribute to the default size transform on the AnimatedContent composable labeled MiddleAnimationLabel.

The gray box is in AnimatedContent and should animate, but the AnimatedContent around it should be a no-op — since contentKey = { it::class } and the target state is always the same class. Btw you'd reproduce the same behavior with contentKey = { "foo" }, and the same workaround (adding an if for the transition spec) would work too. The documentation for AnimatedContent suggests that if the key doesn't change, there shouldn't be any animation at all.

The same workaround (or just adding using(null) to the transition spec) can be applied to AnimatedContent labeled OuterAnimationLabel. Again, it has a constant key so I wouldn't expect any animation to run, regardless of the spec.

Interestingly, this seems related to NewData class having a field with a lambda that captures some object. If you replace line 59 with lambdaWithCapture = { },, the animations behave as expected without any other workarounds.

This reproduces also in an Android project with Kotlin 2.0.0 and Compose BOM 2024.05.00, the desktop project is just simpler to share and iterate on.