[FIX] error occurring in useEffect on hmr/strict mode

[PatrykWalach]

This PR fixes runtime errors thrown during hmr/strict mode.

This on it's own is not enough to make hmr work. Hast to be merged locally with #306 to test hmr.

Rebase of #264

[rbalicki2]

lgtm, just rewrote the comment slightly for grammar and clarity

[rbalicki2]

Sorry, I forgot to do a thorough review before accepting 😂 Do we also need this in useUpdatableDisposableState?

If so, there are probably enough places where we do this that it makes sense to have a useEffectIgnoringHmrAndStrictMode hook.

It might return the lastCommittedParentCache, in which case we don't need to do anything extra in useCachedResponsivePreCommitValue

[PatrykWalach]

The solution used here is not good

• on the first render useEffect will execute (commit and return cleanup)
• on hmr it will cleanup, then the guard will prevent another execute (commit and return cleanup)

so we end up in a cleaned-up state

The reason it doesn't cause any issues now is probably because of gcBuffer.

[rbalicki2]

Ah yeah, you're totally right. Good call re: gcBuffer. I'm going to think about this. I wonder if we need to try to detect HMR/double mounting more directly.

[PatrykWalach]

on useEffect cleanup we will set itemCleanupPairRef to null, if the component unmounted this has no effect, if it was hmr then cache will once again go through temporaryRetain cycle.

This is not tested. It might be easier to test after merging the second pull request.

[PatrykWalach]

Now the cycle is

• commit -> cache is populated
• cleanup -> set maybeHiddenOrFastRefresh to true, clean up cache
  if component is unmounted, that's the end, if it's hmr:
• commit -> read maybeHiddenOrFastRefresh and skip cacheItem.permanentRetainIfNotDisposed so there's no error, repopulate cache

so at the end we are in the populated state.

we don't need to set itemCleanupPairRef to null because cleanup runs just before cache is populated which will override itemCleanupPairRef and there are no renders in between.

useUpdatableDisposableState still needs to be fixed and it can't be fixed in the same way, as there's no way to repopulate 🤔

[PatrykWalach]

I think it's fair to set this to UNASSIGNED_STATE to prevent mutations from firing twice. This was the last piece preventing this PR from being merged @rbalicki2 let me know what you think