fix(form-core): bump _arrayVersion when async defaultValues update array fields by mixelburg · Pull Request #2190 · TanStack/form

mixelburg · 2026-05-21T22:12:19Z

When async defaultValues resolve and update the form, array fields rendered with mode="array" were not re-rendering. This is a regression from #2172 which changed the array field reactivity signal from Object.keys(value ?? []).length to state.meta._arrayVersion. The _arrayVersion counter is bumped on explicit mutations (push/insert/remove/swap/move) but not when defaultValues change asynchronously.

The fix: after the store update in FormApi.update(), iterate over registered fields and bump _arrayVersion for any whose current value is an array. Added a regression test.

Summary by CodeRabbit

Bug Fixes
- Array-mode fields now reliably update and re-render when their values change (including when async/default values are applied), fixing stale array renders.
Tests
- Added a regression test verifying array fields re-render when default values are provided after initial render.
Chores
- Added a patch changeset recording the fix.

…ray fields

coderabbitai · 2026-05-21T22:12:33Z

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packages/react-form/tests/useField.test.tsx

📝 Walkthrough

Walkthrough

FormApi.update now detects array-typed field values and bumps their array metadata versions when values update. A regression test confirms async-resolved array defaultValues re-render the array field, and a changeset records a patch bump for @tanstack/form-core.

Changes

Array Field Async Value Resolution Fix

Layer / File(s)	Summary
Array version bumping on value update `packages/form-core/src/FormApi.ts`	`FormApi.update` now detects array-typed field values within `fieldInfo` and calls `metaHelper(this).bumpArrayVersion(fieldKey)` to trigger metadata updates when values change.
Regression test for async array field resolution `packages/react-form/tests/useField.test.tsx`	New test renders an array field with no initial items, then re-renders with resolved async `defaultValues.people` containing one person, asserting the DOM list and displayed name update correctly.
Changeset metadata `.changeset/nine-beds-shout.md`	Adds a changeset entry bumping `@tanstack/form-core` as a patch and documenting the fix for async array default values.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Suggested reviewers

crutchcorn

Poem

🐰 A little bump, a gentle hop,

Arrays wake up and take their spot,
When defaults arrive from far away,
The form will show them — hip hooray!
Metadata nudged, the fields all play.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: bumping _arrayVersion when async defaultValues update array fields, directly addressing the regression in FormApi.
Description check	✅ Passed	The description includes the issue reference, root cause analysis, and implementation details. However, the PR template checklist items are not checked off, and the release impact section is incomplete.
Linked Issues check	✅ Passed	The PR directly addresses issue `#2178` by implementing the fix: bumping _arrayVersion for array fields when async defaultValues update, and includes a regression test as expected.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to fixing the regression: FormApi.update modification, regression test addition, and changeset entry. No unrelated modifications detected.

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crutchcorn

This fix makes a lot of sense. Thanks for the PR and tests

nx-cloud · 2026-05-26T14:44:39Z

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☁️ Nx Cloud last updated this comment at 2026-05-26 14:59:46 UTC

pkg-pr-new · 2026-05-26T14:47:46Z

More templates

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npm i https://pkg.pr.new/@tanstack/angular-form@2190

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@tanstack/react-form

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@tanstack/react-form-devtools

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@tanstack/react-form-nextjs

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@tanstack/solid-form-devtools

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@tanstack/svelte-form

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commit: 9b21c73

coderabbitai

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@packages/react-form/tests/useField.test.tsx`:
- Line 1546: The test fails because the <ol> element uses the wrong attribute
name `data-mtestid="list"`; update that attribute to `data-testid="list"` so the
test's calls to getByTestId('list') can find the element—search for the <ol> in
the useField.test.tsx test and replace `data-mtestid` with `data-testid` where
the list is rendered.

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packages/react-form/tests/useField.test.tsx

codecov-commenter · 2026-05-26T15:04:37Z

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Codecov Report

❌ Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 91.42%. Comparing base (6892ed0) to head (9b21c73).
⚠️ Report is 229 commits behind head on main.

Files with missing lines	Patch %	Lines
packages/form-core/src/FormApi.ts	80.00%	1 Missing ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2190      +/-   ##
==========================================
+ Coverage   90.35%   91.42%   +1.06%     
==========================================
  Files          38       59      +21     
  Lines        1752     2343     +591     
  Branches      444      585     +141     
==========================================
+ Hits         1583     2142     +559     
- Misses        149      180      +31     
- Partials       20       21       +1

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fix(form-core): bump _arrayVersion when async defaultValues update ar…

7f33ac6

…ray fields

crutchcorn approved these changes May 26, 2026

View reviewed changes

ci: apply automated fixes and generate docs

d1ba30d

crutchcorn added 3 commits May 26, 2026 07:48

chore: add changeset

a771a95

Merge branch 'main' into fix/async-array-default-values

45fb98e

chore: fix eslint

7ca1cbc

coderabbitai Bot reviewed May 26, 2026

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Comment thread packages/react-form/tests/useField.test.tsx Outdated

chore: fix test

9b21c73

crutchcorn merged commit b402d7a into TanStack:main May 26, 2026
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fix(form-core): bump _arrayVersion when async defaultValues update array fields#2190

fix(form-core): bump _arrayVersion when async defaultValues update array fields#2190
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