fix(core): correctly handle state changes during onSubscribe in createStateSourceAction #643
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…eStateSourceAction This fixes a quite subtle bug: Any state changes happening in `onSubscribe` would be not be part of the source.observable. The reason for this is that the implementation would do: 1. First emit the current value by looking at state.get() 2. Invoke the onSubscribe hook. 3. Listen to the observable of state, but skip the first value because we expect it to emit the current state first. However, this means that if (2) actually _changes_ the state synchronously then that's the value that is skipped in (3) happens to be the new state. This changes the implementation to be based around an observable which contains the actual values. This is both shorter in code and also happens to avoid calling `getCurrent` multiple times. Previously `getCurrent` would be invoked twice: Once for detecting that a value had changed and once again when producing the value.
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Description
This fixes a quite subtle bug: Any state changes happening in
onSubscribewould be not be part of the source.observable. The reason for this is that the implementation would do:However, this means that if (2) actually changes the state synchronously then that's the value that is skipped in (3) happens to be the new state.
We're using this pattern in
getDocumentSyncStatus.This changes the implementation to be based around an observable which contains the actual values. This is both shorter in code and also happens to avoid calling
getCurrentmultiple times. PreviouslygetCurrentwould be invoked twice: Once for detecting that a value had changed and once again when producing the value.What to review
withSubscribeHook.Testing
Fun gif
Sorry, I couldn't find any fun gifs about RxJS.