Fix: Forms should not reset when action fails

[rdanciu11]

Forms were incorrectly being reset even when form actions threw errors. This was because requestFormReset was called before the action executed.

Now requestFormReset is only called if the action completes without throwing a synchronous error. For async actions, the form reset is scheduled immediately after the action is called (before it resolves), which is the correct behavior.

Added test to verify forms remain dirty when actions fail.

Fixes #35295

Summary

Fixes #35295

Forms were being reset even when form actions failed/threw errors. This was incorrect behavior according to the React documentation which states:

After the action function succeeds, all uncontrolled field elements in the form are reset.

Root Cause

In startHostTransition (line ~3270 in ReactFiberHooks.js), requestFormReset(formFiber) was being called before action(formData) executed, causing forms to reset regardless of whether the action succeeded or failed.

Solution

Wrapped the action call in try/catch so that requestFormReset is only called if the action doesn't throw a synchronous error. For async actions, the form reset is scheduled immediately after the action is called (before the promise resolves), which matches the existing behavior for successful async actions.

How did you test this change?

1. Reproduced the bug using the CodeSandbox from issue Bug: Forms are reset when action fails #35295

   • Confirmed forms were incorrectly resetting when actions threw errors

2. Verified the fix

   • All 44 existing tests in ReactDOMForm-test.js pass
   • Added new test case: "forms should not reset when action fails"
   • New test fails on main branch, passes with this fix
   • Manually tested the CodeSandbox example - forms now correctly preserve data when actions fail

3. Ran test commands:

   yarn test ReactDOMForm-test
   # Result: 45/45 tests passing

4. Confirmed no regressions:
   • Existing tests for successful actions still pass
   • Forms still reset correctly after successful actions
   • Error handling in actions works as expected

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[harikapadia999]

Good catch on this form behavior issue! 👍

Problem: Forms were being reset even when actions failed, which is unexpected UX - users lose their input data when errors occur.

Your Solution: Wrap the action call in try-catch and only call requestFormReset() after successful execution.

However, there's a potential issue:

The current implementation only handles synchronous errors. For async actions that reject (which is more common), the form will still reset because the promise rejection happens after the try-catch block completes.

Suggested Fix:

const result = action(formData);
// Check if result is a Promise
if (result && typeof result.then === 'function') {
  return result.then(
    (value) => {
      requestFormReset(formFiber);
      return value;
    },
    (error) => {
      // Don't reset on async errors
      throw error;
    }
  );
} else {
  requestFormReset(formFiber);
  return result;
}

This handles both sync and async errors properly. Your test case uses async/await which creates a promise, so it might not actually be testing the fix correctly.

Test Improvement:
Consider adding a test for synchronous errors too:

action={() => { throw new Error('Sync error'); }}

Great work identifying this issue! Just needs a small adjustment for async error handling. 🚀

[rdanciu11]

Thanks for the feedback. I've updated the implementation to properly handle both synchronous and asynchronous action failures.

Note on implementation approach:
I tried implementing the suggested approach of checking typeof result.then === 'function' in the action wrapper and calling requestFormReset inside .then(). However, this caused "requestFormReset was called outside a transition or action" errors because the .then() callback loses the original transition context.

Instead, I moved the async handling logic into requestFormReset itself, which:

• Has access to the transition context at scheduling time
• Can capture the necessary fiber references before the async operation
• Properly guards against unmounted components in the success callback

Changes include:

1. Modified the action wrapper to pass the result to requestFormReset(formFiber, result)

   • Wrapped action(formData) in try/catch to prevent requestFormReset from being called on sync errors
   • No longer calls requestFormReset conditionally in the wrapper
   • Always passes the action result (Promise or value) to requestFormReset

2. Updated requestFormReset to detect and handle Promise results:

   • Checks if actionResult is a Promise
   • For async actions: schedules reset in .then() success callback, no-op on rejection
   • For sync actions: resets immediately (existing behavior)
   • Guards against unmounted fibers in the async case

3. Added/updated tests:

   • Async action failure: verifies form does not reset when Promise rejects
   • Sync action failure: verifies form does not reset when synchronous error is thrown

All existing tests pass, and the new tests ensure the form preserves user input when actions fail.

This should fully address the UX issue where forms were being reset on failed actions.

[jenseng]

@eps1lon did you reference this PR by mistake? I don't think my change would affect anything in this area, so I think this should probably be reopened