Commits on Apr 11, 2021

1. Bugfix: Don't rely on finishedLanes for passive effects …

   I recently started using `pendingPassiveEffectsLanes` to check if there were any pending
   passive effects (530027a). `pendingPassiveEffectsLanes` is the value of
   `root.finishedLanes` at the beginning of the commit phase. When there
   are pending passive effects, it should always be a non-zero value,
   because it represents the lanes used to render the effects.
   
   But it turns out that `root.finishedLanes` isn't always correct.
   Sometimes it's `NoLanes` even when there's a new commit.
   
   I found this while investigating an internal bug report. The only repro
   I could get was via a headless e2e test runner; I couldn't get one in an
   actual browser, or other interactive environment. I used the e2e test to
   bisect and confirm the fix. But I don't know yet know how to write a
   regression test for the precise underlying scenario. I can probably
   reverse engineer one by studying the code; after a quick glance
   at `performConcurrentWorkOnRoot` and `performSyncWorkOnRoot`, it's not
   hard to see how this might happen.
   
   In the meantime, I'll revert the recent change that exposed the bug.
   
   I was surprised that this had never come up before, since the code that
   assigns `root.finishedLanes` is in an extremely hot path, and it hasn't
   changed in a while. The reason is that, before 530027a,
   `root.finishedLanes` was only used by the DevTools profiler, which is
   probably why we had never noticed any issues. In addition to fixing the
   inconsistency, we might also consider making `finishedLanes` a
   profiling-only field.

   

   acdlite committed Apr 11, 2021
   Configuration menu

   • View commit details
   • Copy full SHA for e22a984
   • Browse repository at this point

   Copy the full SHA

   e22a984 View commit details

   Browse the repository at this point in the history