fix: await async onSuccess/onError callbacks to prevent unhandled rejections #4177

shunn2 · 2025-10-26T16:14:27Z

Summary

This PR fixes an issue where useSWRMutation does not await async onSuccess or onError callbacks.
Previously, when developers provided an async callback (for example, revalidating data with mutate(key)), it was executed in parallel with the return of trigger(), leading to race conditions and unhandled promise rejections.

Now, async callbacks are awaited safely, preventing unhandled rejections while maintaining backward compatibility.

Example

const { trigger } = useSWRMutation('/api/item', updateItem, {
  onSuccess: async () => {
    await mutate('/api/item') // unhandled rejection if this fails
  }
})

await trigger({ id: 1 })

Fix

Await onSuccess and onError callbacks inside trigger().
Wrap both in try/catch to prevent callback errors from propagating.
Log callback errors to console.error for visibility.
Preserve existing behavior:
The mutation result and UI state remain unchanged even if a callback fails.
No breaking change for synchronous callbacks.

Related Issue: #4171

…ections

codesandbox-ci · 2025-10-26T16:15:02Z

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fix: await async onSuccess/onError callbacks to prevent unhandled rej…

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…ections

shunn2 requested review from huozhi and shuding as code owners October 26, 2025 16:14

shunn2 changed the title ~~fix: await async onSuccess/onError callbacks to prevent unhandled rej…~~ fix: await async onSuccess/onError callbacks to prevent unhandled rejections Nov 5, 2025

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