Transitions on 3.50.0 don't act the same as 3.49.0

[flayks]

Describe the bug

On a simple "router" using different Page components wrapped with a PageTransition component, the transition with Svelte 3.50.0 does not seem to act the same as before.

The leaving Page component goes out without a transition and then the new one comes with the transition.

As it works with the same exact code on 3.49.0, I believe this is a bug, unless I missed something on the changelog.

Reproduction

Example with Svelte 3.49.0 with transition working as expected:
https://svelte.dev/repl/d498205ea0044e41a37da8f1c0d5728a?version=3.49.0

Same exact example with Svelte 3.50.0, but not acting as wanted this time:
https://svelte.dev/repl/d498205ea0044e41a37da8f1c0d5728a?version=3.50.0

Logs

No response

System Info

REPL

Severity

blocking an upgrade

[jrmoynihan]

Seeing the same thing here. Was trying to debug my own code for a while before I simply reverted to 3.49 to temporarily solve the issue.

[fredguest]

Came here to make the same ticket. 3.50.0 adds at least 100ms of latency between the click and the transition. Very noticeable, had to lock the version to 3.49.0 to avoid it.

[thenbe]

A similar (same?) issue is happening with animate. Only 1 item in a given list is animating, the rest don't play their animations.

[MajorBreakfast]

Wanted to open this now as well :)

Here's my reproduction

Before: https://svelte.dev/repl/d4c3ea5ae72d4b259ef59d91370ea9d0?version=3.49.0
Now (broken): https://svelte.dev/repl/d4c3ea5ae72d4b259ef59d91370ea9d0?version=3.50.0

In Svelte 3.49.0, quickly transitioning works fine

svelte-3.49.0.mov

In Svelte 3.50.0, quickly switching makes it so that there are no visible transitions

svelte-3.50.0.mov

I'm seeing this not just in Safari, but also in Chrome and Firefox

[jrmoynihan]

Wanted to open this now as well :)

Here's my reproduction

Before: https://svelte.dev/repl/d4c3ea5ae72d4b259ef59d91370ea9d0?version=3.49.0 Now (broken): https://svelte.dev/repl/d4c3ea5ae72d4b259ef59d91370ea9d0?version=3.50.0

In Svelte 3.49.0, quickly transitioning works fine

svelte-3.49.0.mov
In Svelte 3.50.0, quickly switching makes it so that there are no visible transitions

svelte-3.50.0.mov
I'm seeing this not just in Safari, but also in Chrome and Firefox

To be specific, it looks like the transitions run once. I think they're getting removed by mistake after the first transition occurs.

[baseballyama]

I would appreciate it if you could check this PR and confirm that it works as expected.

#7831

[ScriptRaccoon]

The flip animations also do not work anymore.

https://svelte.dev/repl/da3494c42f1745fe9e342860e7404bb1?version=3.49.0 (works)
https://svelte.dev/repl/da3494c42f1745fe9e342860e7404bb1?version=3.50.0 (doesn't work)