Pre-reset field validation completion clears a newer validation status

[lunaxislu]

Describe the bug

A field validation started before form.reset() can clear the validation status of a newer run when the older run finishes. A UI reading field.state.meta.isValidating can stop displaying its checking indicator while the new validation is still pending.

This is a follow-up to the review discussion on #2382. The counter race reproduces on that PR's base as well as its head; it is separate from the stale-error fix in #2381/#2382.

Your minimal, reproducible example

Tests-only commit with unchanged main production code

git clone https://github.com/lunaxislu/form.git
cd form
git checkout ba6de4a83142fafcb74d5763f7e6574067019b14
# Use Node 24.8.0 from .nvmrc and pnpm via Corepack.
corepack pnpm install --frozen-lockfile
corepack pnpm --dir packages/form-core exec vitest run tests/FieldApi.spec.ts -t 'should preserve pending validation when an older run settles'

The four cases use deferred promises and fake timers. The two reset cases fail; the two no-reset controls pass. Both direct and linked-field validation are covered.

Steps to reproduce

1. Start validation A via a field's onChangeAsync and leave its promise pending.
2. Call form.reset().
3. Blur the field to start validation B via onBlurAsync and leave B pending.
4. Resolve A.
5. Observe that the field's isValidating becomes false even though B is pending.

A starts       count=1, isValidating=true
reset          count=0, isValidating=false
B starts       count=1, isValidating=true
A settles      count=0, isValidating=false  <-- B is still pending
B settles      count=0, isValidating=false

Using different validation causes avoids the same-cause debounce timer issue tracked by #2372/#2373. The linked-field variant starts A by changing another field listed in onChangeListenTo.

Expected behavior

After reset, a completion belonging to a pre-reset run should not decrement the new run's counter. field.state.meta.isValidating should remain true until B settles. Without reset, overlapping runs should still decrement normally (2 → 1 → 0).

How often does this bug happen?

Every time with the controlled ordering above.

Platform

macOS; reproduced in the form-core Vitest suite with jsdom, without a browser UI or server dependency.

TanStack Form adapter

vanilla (@tanstack/form-core)

TanStack Form version

1.33.5, main source at 57a855b42b9b99cee5ca12890b70c7df84e2982c.

TypeScript version

5.9.3

Additional context

Reset replaces field metadata, including _pendingValidationsCount. The outer completion block of FieldApi.validateAsync still calls endValidation() against current metadata without distinguishing a pre-reset run. This applies to the main field and linked fields.

The report concerns completion accounting across a full form reset. It does not request changes to debounce scheduling, per-field reset, or form/group-level validation. Searches for reset/counter/isValidating and related reports did not reveal a separate report for this exact sequence beyond the #2382 review discussion.