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

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Merged
TomatoToaster merged 1 commit into from
Dec 29, 2021
Merged

[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();

@TomatoToaster TomatoToaster Dec 29, 2021

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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.

@mananjadhav mananjadhav Dec 29, 2021

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Agreed.

@TomatoToaster TomatoToaster Dec 29, 2021

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Dope then I think it's safe to merge!

@roryabraham roryabraham Dec 29, 2021

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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 💥

@mananjadhav mananjadhav Dec 29, 2021

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Noted. Thanks for the explanation :)

};
}
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