Commits on Sep 21, 2022

1. Fix memory leak after repeated setState bailouts …

   There's a global queue (`concurrentQueues` in the
   ReactFiberConcurrentUpdates module) that is cleared at the beginning of
   each render phase.
   
   However, in the case of an eager `setState` bailout where the state is
   updated to same value as the current one, we add the update to the queue
   without scheduling a render. So the render phase never removes it from
   the queue. This can lead to a memory leak if it happens repeatedly
   without any other updates.
   
   There's only one place where this ever happens, so the fix was pretty
   straightforward.
   
   Currently there's no great way to test this from a Jest test, so I
   confirmed locally by checking in an existing test whether the array gets
   reset. @sompylasar had an interesting suggestion for how to catch these
   in the future: in the development build (perhaps behind a flag), use a
   Babel plugin to instrument all module-level variables. Then periodically
   sweep to confirm if something has leaked. The logic is that if there's
   no React work scheduled, and a module-level variable points to an
   object, it very likely indicates a memory leak.

   

   acdlite committed Sep 21, 2022
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