fix(form-core): treat non-plain objects with no own enumerable keys as unequal in evaluate by Zelys-DFKH · Pull Request #2140 · TanStack/form

Zelys-DFKH · 2026-04-30T19:22:33Z

🎯 Changes

evaluate() compares objects by iterating Object.keys(). That works fine for plain objects, but for anything whose state lives only in getters, Object.keys() returns []. The key-iteration loop then vacuously succeeds and two distinct instances are treated as equal, regardless of what they actually contain. Temporal.Duration, RegExp, any class that exposes values through getters — they all hit this. The result is that form updates get dropped silently when a field value changes to a new instance of such a type.

The fix is a single guard placed after the key-count check:

if (
  keysA.length === 0 &&
  !Array.isArray(objA) &&
  !Array.isArray(objB) &&
  (Object.getPrototypeOf(objA) !== Object.prototype ||
    Object.getPrototypeOf(objB) !== Object.prototype)
) {
  return false
}

When both objects have zero own enumerable keys and at least one isn't a plain {}, they fall back to referential inequality (Object.is at the top already returned false). Arrays get an explicit carve-out so evaluate([], []) still returns true.

PR #1939 adds a specific instanceof Blob guard for File/Blob. This guard is more general and covers the same case, plus Temporal, RegExp, Error, and anything else with a getter-only design. If #1939 merges first, its instanceof Blob check fires before reaching this one, so there's no conflict. If this merges first, File/Blob is already covered.

One thing to flag: two RegExp literals with identical source and flags (like /abc/g vs /abc/g) now return false, since they're different instances. Previously they returned true vacuously, which was also wrong: it suppressed updates when a regex field actually changed. The behavior is now in the right direction. A dedicated instanceof RegExp handler (like the existing Date one) could add semantic equality if that turns out to be useful.

✅ Checklist

I have followed the steps in the Contributing guide.
I have tested this code locally with pnpm test:pr.

🚀 Release Impact

This change affects published code, and I have generated a changeset.
This change is docs/CI/dev-only (no release).

Summary by CodeRabbit

Release Notes

Bug Fixes
- Fixed form validation comparison logic that was incorrectly treating distinct non-plain objects as equivalent. This affected special object types including Temporal, RegExp, and classes with getter-only properties.
- Strengthened test coverage to ensure accurate object comparison behavior across all supported object types.

…s unequal in evaluate

coderabbitai · 2026-04-30T19:22:45Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 70aa1d66-a278-41d6-b7eb-9a24ebc591e9

📥 Commits

Reviewing files that changed from the base of the PR and between 93be6f0 and 1b02d59.

📒 Files selected for processing (3)

.changeset/fix-evaluate-getter-only-objects.md
packages/form-core/src/utils.ts
packages/form-core/tests/utils.spec.ts

📝 Walkthrough

Walkthrough

This patch fixes the evaluate() function in @tanstack/form-core to correctly distinguish non-plain objects with zero own enumerable keys (such as Temporal types, RegExp, Date, or getter-only class instances) by returning false instead of treating them as equal, preventing silent form option update failures.

Changes

Cohort / File(s)	Summary
Changeset Documentation `.changeset/fix-evaluate-getter-only-objects.md`	Declares patch version bump for `@tanstack/form-core` documenting the fix for `evaluate()` incorrectly treating distinct non-plain objects as equal.
Core Comparison Logic `packages/form-core/src/utils.ts`	Adds a guard check to `evaluate()` that returns `false` when both inputs are non-array objects with no own enumerable keys and non-`Object.prototype` prototypes, preventing false positives from key iteration never executing.
Test Coverage `packages/form-core/tests/utils.spec.ts`	Adds comprehensive test assertions validating that distinct non-plain objects (getter-based instances, Temporal types, RegExp) evaluate as unequal, while plain empty objects remain equal, and cross-type comparisons behave correctly.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 A guard to catch the sneaky trick,
When objects hide with no keys quick,
Now Temporal and Date alike,
Won't fool our form—equality struck right! ✨

🚥 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 summarizes the main fix: treating non-plain objects with no own enumerable keys as unequal in the evaluate function.
Description check	✅ Passed	The description is comprehensive, addressing the root cause, the fix details, interaction with other PRs, and includes all required checklist items marked complete.
Linked Issues check	✅ Passed	The PR successfully addresses issue `#1628` by implementing the required guard to prevent distinct non-plain objects with no enumerable keys from being treated as equal.
Out of Scope Changes check	✅ Passed	All changes are directly related to fixing the evaluate() function logic for non-plain objects, with corresponding tests and changeset documentation.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

Create PR with unit tests

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

_{Review rate limit: 7/8 reviews remaining, refill in 7 minutes and 30 seconds.}

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

crutchcorn

This is great, thanks!

nx-cloud · 2026-05-10T19:46:17Z

View your CI Pipeline Execution ↗ for commit 1b02d59

Command	Status	Duration	Result
`nx affected --targets=test:sherif,test:knip,tes...`	✅ Succeeded	2m 13s	View ↗
`nx run-many --target=build --exclude=examples/**`	✅ Succeeded	33s	View ↗

☁️ Nx Cloud last updated this comment at 2026-05-10 19:48:52 UTC

pkg-pr-new · 2026-05-10T19:47:21Z

More templates

@tanstack/angular-form

npm i https://pkg.pr.new/@tanstack/angular-form@2140

@tanstack/form-core

npm i https://pkg.pr.new/@tanstack/form-core@2140

@tanstack/form-devtools

npm i https://pkg.pr.new/@tanstack/form-devtools@2140

@tanstack/lit-form

npm i https://pkg.pr.new/@tanstack/lit-form@2140

@tanstack/react-form

npm i https://pkg.pr.new/@tanstack/react-form@2140

@tanstack/react-form-devtools

npm i https://pkg.pr.new/@tanstack/react-form-devtools@2140

@tanstack/react-form-nextjs

npm i https://pkg.pr.new/@tanstack/react-form-nextjs@2140

@tanstack/react-form-remix

npm i https://pkg.pr.new/@tanstack/react-form-remix@2140

@tanstack/react-form-start

npm i https://pkg.pr.new/@tanstack/react-form-start@2140

@tanstack/solid-form

npm i https://pkg.pr.new/@tanstack/solid-form@2140

@tanstack/solid-form-devtools

npm i https://pkg.pr.new/@tanstack/solid-form-devtools@2140

@tanstack/svelte-form

npm i https://pkg.pr.new/@tanstack/svelte-form@2140

@tanstack/vue-form

npm i https://pkg.pr.new/@tanstack/vue-form@2140

commit: 1b02d59

sentry · 2026-05-10T19:49:10Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.29%. Comparing base (6892ed0) to head (1b02d59).
⚠️ Report is 200 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2140      +/-   ##
==========================================
- Coverage   90.35%   90.29%   -0.07%     
==========================================
  Files          38       49      +11     
  Lines        1752     2050     +298     
  Branches      444      538      +94     
==========================================
+ Hits         1583     1851     +268     
- Misses        149      179      +30     
  Partials       20       20

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

fix(form-core): treat non-plain objects with no own enumerable keys a…

1b02d59

…s unequal in evaluate

crutchcorn approved these changes May 10, 2026

View reviewed changes

crutchcorn merged commit 5dd1ed4 into TanStack:main May 10, 2026
9 checks passed

github-actions Bot mentioned this pull request May 10, 2026

ci: Version Packages #2168

Merged

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

fix(form-core): treat non-plain objects with no own enumerable keys as unequal in evaluate#2140

fix(form-core): treat non-plain objects with no own enumerable keys as unequal in evaluate#2140
crutchcorn merged 1 commit into
TanStack:mainfrom
Zelys-DFKH:fix/evaluate-getter-only-objects

Zelys-DFKH commented Apr 30, 2026 •

edited by coderabbitai Bot

Loading

Uh oh!

coderabbitai Bot commented Apr 30, 2026 •

edited

Loading

Walkthrough

Changes

Estimated code review effort

Poem

❌ Failed checks (1 warning)

Uh oh!

crutchcorn left a comment

Uh oh!

nx-cloud Bot commented May 10, 2026 •

edited

Loading

Uh oh!

pkg-pr-new Bot commented May 10, 2026

Uh oh!

sentry Bot commented May 10, 2026

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

Uh oh!

Conversation

Zelys-DFKH commented Apr 30, 2026 • edited by coderabbitai Bot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

🎯 Changes

✅ Checklist

🚀 Release Impact

Summary by CodeRabbit

Release Notes

Uh oh!

coderabbitai Bot commented Apr 30, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Walkthrough

Changes

Estimated code review effort

Poem

❌ Failed checks (1 warning)

Uh oh!

crutchcorn left a comment

Choose a reason for hiding this comment

Uh oh!

nx-cloud Bot commented May 10, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

pkg-pr-new Bot commented May 10, 2026

Uh oh!

sentry Bot commented May 10, 2026

Codecov Report

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

Zelys-DFKH commented Apr 30, 2026 •

edited by coderabbitai Bot

Loading

coderabbitai Bot commented Apr 30, 2026 •

edited

Loading

nx-cloud Bot commented May 10, 2026 •

edited

Loading