fix(svelte-query): shrink useMutationState results by alex-js-ltd · Pull Request #11153 · TanStack/query

alex-js-ltd · 2026-08-08T10:19:51Z

Changes

useMutationState() in @tanstack/svelte-query only ever grew its returned
array. The cache-subscription callback updated the underlying $state array
with Object.assign(result, nextResult), but Array.prototype.length is
non-enumerable, so Object.assign never truncates result when the new
result set is shorter. Once a mutation stopped matching filters (settled,
was removed/GC'd, or a narrower filter was applied), its stale entry stayed
in the array forever.

Fix: replace the Object.assign with result.splice(0, result.length, ...nextResult),
which replaces the array's contents in place — including truncating it —
while preserving the $state array's reference identity (required by the rune).

Includes a regression test that starts two mutations matching
filters: { status: 'pending' }, lets both settle, and asserts the returned
array goes back to [] instead of keeping the two stale "pending" entries.

✅ Checklist

I have followed the steps in the Contributing guide.
I have tested this code locally with pnpm run 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

Bug Fixes
- Fixed useMutationState so mutations are removed from filtered results when they no longer match the selected criteria.
- Improved reactive updates to keep mutation state results accurate as statuses change, including transitions away from pending.
Tests
- Added coverage confirming that mutations are removed when they no longer match a pending-status filter.
- Verified filtered mutation results remain synchronized after status updates.

…red results

coderabbitai · 2026-08-08T10:21:50Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 1b8fbfd9-caa3-4939-b1c3-d51f0570b358

📥 Commits

Reviewing files that changed from the base of the PR and between 16b6671 and 9b20de9.

📒 Files selected for processing (3)

.changeset/svelte-query-usemutationstate-filter-shrink.md
packages/svelte-query/src/useMutationState.svelte.ts
packages/svelte-query/tests/useMutationState/useMutationState.svelte.test.ts

🚧 Files skipped from review as they are similar to previous changes (3)

packages/svelte-query/tests/useMutationState/useMutationState.svelte.test.ts
packages/svelte-query/src/useMutationState.svelte.ts
.changeset/svelte-query-usemutationstate-filter-shrink.md

Included review availability: Your plan provides up to 10 included reviews per hour; 9 remain after this review.

📝 Walkthrough

Walkthrough

useMutationState now removes mutations that no longer match its filters. A regression test covers completed pending mutations, and a patch changeset documents the fix.

Changes

Mutation filter result updates

Layer / File(s)	Summary
Replace stale filtered results `packages/svelte-query/src/useMutationState.svelte.ts`, `packages/svelte-query/tests/useMutationState/useMutationState.svelte.test.ts`, `.changeset/svelte-query-usemutationstate-filter-shrink.md`	The reactive result array now uses `splice` to match the current filtered results. The test verifies that completed pending mutations produce an empty result. A patch changeset records the fix.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 9b20d

This localized fix makes the returned mutation-state array correctly shrink when entries stop matching, while preserving the existing array reference. No actionable merge-blocking risk remains beyond normal checks and review.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main fix: shrinking stale useMutationState results in Svelte Query.
Description check	✅ Passed	The description explains the bug, root cause, fix, regression test, checklist, and release impact.
Linked Issues check	✅ Passed	The changes directly address issue `#11152` by removing stale filtered mutations while preserving array identity and adding regression coverage.
Out of Scope Changes check	✅ Passed	All code, test, and changeset updates directly support the linked issue and stated pull request objectives.
Docstring Coverage	✅ Passed	Docstring check was indeterminate for this PR — some files could not be analyzed in time. Not blocking.

✨ Finishing Touches

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Create PR with unit tests

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Michael-Obele · 2026-08-24T11:09:58Z

Yeah. This checks out. Thanks for the commit!

Michael-Obele

This is great. Thanks

coderabbitai · 2026-08-24T12:33:36Z

Note

GitHub couldn't provide a complete incremental comparison for this pull request, so CodeRabbit is performing a full review instead. This review may take a little longer.

nx-cloud · 2026-08-24T12:33:59Z

View your CI Pipeline Execution ↗ for commit 9b20de9

Command	Status	Duration	Result
`nx affected --targets=test:sherif,test:knip,tes...`	✅ Succeeded	4m 26s	View ↗
`nx run-many --target=build --exclude=examples/*...`	✅ Succeeded	7s	View ↗

☁️ Nx Cloud last updated this comment at 2026-08-24 12:39:16 UTC

pkg-pr-new · 2026-08-24T12:36:03Z

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commit: 9b20de9

alex-js-ltd added 3 commits August 8, 2026 10:53

test(svelte-query/useMutationState): add coverage for shrinking filte…

4d003d0

…red results

fix(svelte-query): shrink useMutationState results

85079bd

chore: add changeset for useMutationState fix

9f71f4f

Michael-Obele approved these changes Aug 24, 2026

View reviewed changes

Michael-Obele mentioned this pull request Aug 24, 2026

fix(svelte-query): useMutationState array never shrank when mutations stopped matching filter #11254

Closed

Merge branch 'main' into fix/svelte-query-usemutationstate-array-shrink

9b20de9

TkDodo merged commit 250050d into TanStack:main Aug 24, 2026
9 checks passed

github-actions Bot mentioned this pull request Aug 24, 2026

ci: Version Packages #11271

Merged

alex-js-ltd mentioned this pull request Aug 24, 2026

useMutationState does not update when filters change (react-query) #11272

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fix(svelte-query): shrink useMutationState results - #11153

fix(svelte-query): shrink useMutationState results#11153
TkDodo merged 4 commits into
TanStack:mainfrom
alex-js-ltd:fix/svelte-query-usemutationstate-array-shrink

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