feat: warn on async subscriber to onAuthStateChange #1062
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hf
reviewed
May 16, 2025
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| if (callback.constructor.name === 'AsyncFunction') { | ||
| console.warn( | ||
| 'Calling onAuthStateChange with an async function may cause a deadlock.' | ||
| + ' For a solution please see the docs: ' + | ||
| 'https://supabase.com/docs/reference/javascript/auth-onauthstatechange' | ||
| ) | ||
| } |
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In and of itself there is no problem subscribing an async function, but the problem arises if you use another Supabase Client Library within, and that is almost impossible to detect reliably :(
If you want, you can try to find a way -- maybe setting a boolean on the object and checking it in any other auth-js method?
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Yep, I totally agree. I couldn't think of any elegant way of dealing with this but wanted to help minimise the chance of someone else spending half a day getting confused by a race condition. 🙂
Perhaps this warning could only be displayed if the debug flag was set to true?
Certainly if it's not called with an Async function then it can't deadlock.
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What kind of change does this PR introduce?
Feature to warn developers that subscribing to onAuthStateChange with an async function might cause problems.
What is the current behavior?
Currently no warning is issued either when subscribing, or when calling other supabase functions from inside the onAuthStateChange subscriber leading to the supabase-js client silently hanging. Related issue: supabase/supabase-js#1401
What is the new behavior?
The new behaviour results in the developer being warned that they have subscribed with an async function.
Additional context
I couldn't get the tests to run locally so this PR may not be functioning correctly.