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feat: warn on async subscriber to onAuthStateChange #1062

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feat: warn on async subscriber to onAuthStateChange #1062

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8 changes: 8 additions & 0 deletions src/GoTrueClient.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -1847,6 +1847,14 @@ export default class GoTrueClient {
): {
data: { subscription: Subscription }
} {
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'
)
}
Comment on lines +1850 to +1856
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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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@AJamesPhillips AJamesPhillips May 16, 2025 •
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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.


const id: string = uuid()
const subscription: Subscription = {
id,
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28 changes: 28 additions & 0 deletions test/GoTrueClient.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -814,6 +814,34 @@ describe('The auth client can signin with third-party oAuth providers', () => {
})
})

describe('Developers are warned if subscribing with an async function', () => {
const originalWarn = console.warn
let warnings: any[][] = []

beforeEach(() => {
console.warn = (...args: any[]) => {
console.log('WARN', ...args)

warnings.push(args)
}
})

afterEach(() => {
console.warn = originalWarn
warnings = []
})

test('Subscribing a non-async listener should not log a warning', async () => {
authSubscriptionClient.onAuthStateChange(() => console.log('onAuthStateChange was called'))
expect(warnings.length).toEqual(0)
})

test('Subscribing an async listener should log a warning', async () => {
authSubscriptionClient.onAuthStateChange(async () => console.log('onAuthStateChange was called'))
expect(warnings.length).toEqual(1)
})
})

describe('Sign Up Enabled', () => {
test('User can sign up', async () => {
const { email, password } = mockUserCredentials()
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