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[No QA] fix: null check for app state subscription added #6936

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merged 1 commit into from
Dec 29, 2021
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[No QA] fix: null check for app state subscription added #6936

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3 changes: 3 additions & 0 deletions src/libs/AppStateMonitor/index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,9 @@ function addBecameActiveListener(callback) {
}
const appStateChangeSubscription = AppState.addEventListener('change', appStateChangeCallback);
return () => {
if (!appStateChangeSubscription) {
return;
}
appStateChangeSubscription.remove();
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I think this code change still makes sense regardless right? It might be redundant with the RN upgrade if that makes it so appStateChangeSubscription is never null, but it wouldn't hurt to have this check.

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Agreed.

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Dope then I think it's safe to merge!

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FWIW, I think including the null check is a good idea even in RN 0.65+, because, while unlikely, I think we could potentially have a race condition like this if a component mounts and unmounts almost instantly:

  1. Constructor initializes appStateChangeSubscription to null.
  2. Component mounts, componentDidMount runs and starts creating the subscription.
  3. Component unmounts and componentWillUnmount runs before componentDidMount finishes creating the subscription. So the subscription is still null 💥

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Noted. Thanks for the explanation :)

};
}
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