fix(form-core): 🐛 File input field - Picking a different file does not trigger rerender (deep equality issue with File/Blob objects) by joaoGabriel55 · Pull Request #1939 · TanStack/form

joaoGabriel55 · 2025-12-15T18:24:13Z

Issue: #1932

🎯 Changes

Add support for file values with UUID in setFieldValue

✅ 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).

changeset-bot · 2025-12-15T18:24:16Z

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packages/form-core/tests/FormApi.spec.ts

LeCarbonator · 2025-12-17T17:25:17Z

packages/form-core/src/utils.ts

 * @private
 */
 export function setBy(obj: any, _path: any, updater: Updater<any>) {
+  const isFile = updater instanceof File


React Native does not have File defined and will throw a ReferenceError. You cannot implement the fix this way.

Oh. Truly. Good catch, thanks!

nx-cloud · 2025-12-17T17:26:22Z

View your CI Pipeline Execution ↗ for commit df74f02

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`nx run-many --target=build --exclude=examples/**`	✅ Succeeded	34s	View ↗

☁️ Nx Cloud last updated this comment at 2025-12-19 08:23:26 UTC

pkg-pr-new · 2025-12-17T19:10:43Z

More templates

@tanstack/angular-form

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@tanstack/lit-form

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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/react-form-remix

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@tanstack/svelte-form

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@tanstack/vue-form

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commit: df74f02

codecov · 2025-12-17T19:11:09Z

Codecov Report

❌ Patch coverage is 66.66667% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.25%. Comparing base (6892ed0) to head (df74f02).
⚠️ Report is 111 commits behind head on main.

Files with missing lines	Patch %	Lines
packages/form-core/src/utils.ts	66.66%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1939      +/-   ##
==========================================
- Coverage   90.35%   89.25%   -1.11%     
==========================================
  Files          38       48      +10     
  Lines        1752     1954     +202     
  Branches      444      498      +54     
==========================================
+ Hits         1583     1744     +161     
- Misses        149      189      +40     
- Partials       20       21       +1

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…trigger-rerender' of github-personal.com:joaoGabriel55/form into fix/file-input-field-picking-a-different-file-does-not-trigger-rerender

LeCarbonator

It looks like the previous comment hasn't been addressed between the previous review and this review request.

The actual required changes don't look that bad, though. Perhaps I'll have some time to help out later this week with that.

LeCarbonator · 2026-01-06T06:35:57Z

packages/form-core/src/utils.ts

    if (!path.length) {
-      return functionalUpdate(updater, parent)
+      return functionalUpdate(
+        isFile(updater) ? { file: updater, uuid: uuid() } : updater,


This isn't type safe. This wrongly asserts File field values as { file: File | (oldFile: File) => File, uuid: string } instead of

actually running the updater

Preserving the expected field value's structure

LeCarbonator · 2026-01-06T06:36:43Z

packages/form-core/src/utils.ts

 }

 export function evaluate<T>(objA: T, objB: T) {
+  if (objA instanceof File && objB instanceof File) {


It looks like the previous comment wasn't addressed, despite the request for another review. This will throw ReferenceErrors in environments where File is not present (such as React Native).

LeCarbonator · 2026-01-06T06:39:22Z

packages/form-core/tests/FormApi.spec.ts

+  const firstFile = new File(['first'], 'first.png', { type: 'image/png' })
+  form.setFieldValue('avatar', firstFile)
+
+  const firstValue = form.state.values.avatar as { file: File; uuid: string }


These type assertions are a huge problem. It cannot stay.

Luckily, as long as evaluate properly handles File types, this whole uuid trickery won't be needed. Just make sure to add unit tests for a File comparison with evaluate. I believe the existing tests can be found in utils.spec.ts.

fix: Add support for file values with uuid in setFieldValue

f461a64

fernandollisboa reviewed Dec 15, 2025

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joaoGabriel55 added 2 commits December 15, 2025 16:44

test: Fix test descriptions and assertions for file value with uuid

52899a3

Move file handling logic from FormApi to setBy utility

e52c1a6

LeCarbonator requested changes Dec 17, 2025

View reviewed changes

ci: apply automated fixes and generate docs

9145eca

joaoGabriel55 added 2 commits December 18, 2025 11:11

patch: Add isFile utility and use it for file value checks

45c3e2a

Merge branch 'fix/file-input-field-picking-a-different-file-does-not-…

df74f02

…trigger-rerender' of github-personal.com:joaoGabriel55/form into fix/file-input-field-picking-a-different-file-does-not-trigger-rerender

joaoGabriel55 requested a review from LeCarbonator January 5, 2026 11:00

LeCarbonator requested changes Jan 6, 2026

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fix(form-core): 🐛 File input field - Picking a different file does not trigger rerender (deep equality issue with File/Blob objects)#1939

fix(form-core): 🐛 File input field - Picking a different file does not trigger rerender (deep equality issue with File/Blob objects)#1939
joaoGabriel55 wants to merge 6 commits intoTanStack:mainfrom
joaoGabriel55:fix/file-input-field-picking-a-different-file-does-not-trigger-rerender

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