fix(solid-query): follow queryClient changes in useMutation 🤖🤖🤖 by dijedontahiri · Pull Request #11545 · TanStack/query

dijedontahiri · 2026-09-19T06:37:47Z

🎯 Changes

useMutation resolves a reactive custom queryClient accessor, but its MutationObserver was constructed once from the initial client. Switching the accessor therefore left subsequent mutate() calls on the previous client's defaults/cache and kept the exposed result tied to the old observer.

This change swaps to a fresh MutationObserver when the resolved client changes, resets the exposed state to that observer, and makes mutate() always use the current observer.

The review also exposed an important callback-lifecycle edge case: simply unsubscribing the old observer while one of its mutations is pending suppresses that mutation's per-call callbacks, because MutationObserver only delivers them while it still has listeners. The final implementation therefore retains a state-isolated subscription to an outgoing pending observer until it settles, and releases that subscription either on settlement or component cleanup. Results from the retained observer are never written into the new client's state.

Regression coverage now verifies all three behaviors:

after switching clients, new mutations use the new client's defaults/cache;
an in-flight old-client mutation still delivers its per-call callback after the client switch;
the retained callback is not delivered after the component itself unmounts.

Validation

Exact final candidate: 0606ea9da15f4f8fbc761ffb0aca6593729d6b48
Exact base: d346e85f0144eb9b991e6e1665b22f4574de9751

Hosted immutable-head validation: https://github.com/dijedontahiri/query/actions/runs/35428513719

The validation checked out the exact final candidate SHA and verified meaningful negative controls before running the final tree:

exact upstream-base useMutation.ts + the final regression file: the queryClient-switch regression fails while the unrelated unmount control passes;
original PR candidate 36990befc39232df24b016b204d393f6d412487d + the final regression file: the basic client-switch regression passes, but the new in-flight per-call callback regression fails while the unmount control passes;
exact final candidate: all focused regressions pass.

Final-tree checks all passed:

pnpm nx run @tanstack/solid-query:test:lib --skip-nx-cache
pnpm nx run @tanstack/solid-query:test:types --skip-nx-cache across the repository's configured TypeScript matrix
pnpm nx run @tanstack/solid-query:test:eslint --skip-nx-cache
pnpm nx run @tanstack/solid-query:build --skip-nx-cache
pnpm nx run @tanstack/solid-query:test:build --skip-nx-cache
pnpm run generate-docs with no generated diff
pnpm run test:pr --base=d346e85f0144eb9b991e6e1665b22f4574de9751 --head=0606ea9da15f4f8fbc761ffb0aca6593729d6b48 --skip-nx-cache --parallel=2
Prettier, git diff --check, exact-head verification, and exact three-file contribution-scope audit.

A patch changeset for @tanstack/solid-query is included.

Automated-agent disclosure: this PR was prepared, tested, updated, and submitted through TanStack Query's documented 🤖🤖🤖 automated-agent opt-in route. It does not claim independent human review.

✅ Checklist

I have followed the steps in the Contributing guide.
I have tested code changes with the repository's pnpm run test:pr flow and the focused/package checks listed above.
I fully understand the code in this pull request, including any code generated with AI assistance. This is an automated-agent submission; the agent verified the root cause, negative controls, final diff, and tests, but does not claim personal human understanding or independent human review.

🚀 Release Impact

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

coderabbitai · 2026-09-19T06:38:16Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository: TanStack/query/.coderabbit.yaml

Review profile: CHILL

Plan: Advanced

Run ID: a9b17e28-730e-4762-ab61-31cfaf33f206

📥 Commits

Reviewing files that changed from the base of the PR and between a7fbcca and 0606ea9.

📒 Files selected for processing (1)

packages/solid-query/src/useMutation.ts

🚧 Files skipped from review as they are similar to previous changes (1)

packages/solid-query/src/useMutation.ts

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

📝 Walkthrough

Walkthrough

useMutation now follows a reactive QueryClient change, recreates its observer, retains pending callbacks, and releases subscriptions during cleanup. Integration tests cover client switching, in-flight mutations, and unmount behavior.

Changes

Mutation client switching

Layer / File(s)	Summary
Observer recreation and pending retention `packages/solid-query/src/useMutation.ts`, `.changeset/solid-mutation-client-switch.md`	`useMutation` recreates its `MutationObserver` when the reactive `queryClient` accessor returns a different client. It retains pending observer subscriptions and releases them during cleanup. The changeset documents a patch release.
Client switch regression coverage `packages/solid-query/src/__tests__/useMutation.queryClient.test.tsx`	Tests verify client-specific mutation results and cache counts, pending callback delivery after a client switch, and callback suppression after unmount.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix · Severity of issue fixed: Medium

Sequence Diagram(s)

sequenceDiagram
  participant QueryClientAccessor
  participant useMutation
  participant MutationObserver
  QueryClientAccessor->>useMutation: provide current QueryClient
  useMutation->>MutationObserver: create observer
  QueryClientAccessor->>useMutation: provide changed QueryClient
  useMutation->>MutationObserver: retain pending observer and unsubscribe
  useMutation->>MutationObserver: create observer for changed client
  MutationObserver->>useMutation: update mutation result

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 25.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 4 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	For `#11544`, `useMutation` stores the current `MutationObserver` and watches the resolved `queryClient` accessor. On a client change, it retains pending callbacks, unsubscribes the old observer, create…
Out of Scope Changes check	✅ Passed	The changes are limited to the `useMutation` implementation, focused regression tests, and a patch changeset for `@tanstack/solid-query`. These changes directly support `#11544`. No unrelated change is …
Title check	✅ Passed	The title clearly and concisely describes the main change: updating Solid Query useMutation to follow queryClient changes. The emojis add minor noise but do not obscure the meaning.
Description check	✅ Passed	The description is complete and relevant. It explains the motivation, implementation, regression coverage, validation results, checklist status, release impact, and changeset. The unchecked understand…

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Copilot

Copilot review overview

🟡 Changes recommended

Preserve per-call callback execution for in-flight mutations when switching clients.

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Review effort: Lite
Findings: 1

Open (1)

Preserve callbacks for pending mutations after client switching · New

What changed in this PR

Updates Solid Query’s useMutation to follow reactive QueryClient changes by replacing its mutation observer.

Changes:

Recreates and subscribes to an observer for the current client.
Adds client-switching regression tests.
Adds a patch changeset.

File	Summary
`packages/solid-query/src/useMutation.ts`	Observer lifecycle updated; critical unresolved issue: switching clients can suppress callbacks for in-flight mutations (1 vote).
`packages/solid-query/src/__tests__/useMutation.queryClient.test.tsx`	Tests client-specific mutation behavior.
`.changeset/solid-mutation-client-switch.md`	Records the patch release.

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dijedontahiri · 2026-09-19T07:14:50Z

+    on(
+      client,
+      (nextClient) => {
+        unsubscribe()


Confirmed and fixed on the current head 0606ea9da15f4f8fbc761ffb0aca6593729d6b48.

The final implementation retains a state-isolated subscription to an outgoing observer only while its mutation is pending. That keeps the per-call callback lifecycle alive without allowing the old observer to update the new client's exposed state; the retained subscription is released when the old mutation settles or when the component unmounts.

I added two focused regressions around this review case. In immutable-head validation, the original PR candidate 36990befc39232df24b016b204d393f6d412487d passes the basic client-switch test but fails should preserve per-call callbacks for an in-flight mutation after switching clients; the final head passes that test plus the unmount cleanup control. The full Solid unit/type/lint/build/publication checks and root test:pr also pass on the exact final head: https://github.com/dijedontahiri/query/actions/runs/35428513719

Automated-agent reply under the PR's 🤖🤖🤖 route.

…itch

Dijedon added 6 commits September 19, 2026 08:09

fix(solid-query): follow reactive mutation query client

eff4c19

test(solid-query): cover mutation client switching

7b7a281

chore: add solid query client switch changeset

7f606a3

chore(solid-query): format mutation client switch

e88f53d

refactor(solid-query): keep mutation observer replacement local

94dbb42

chore(solid-query): format mutation observer result type

36990be

Copilot AI reviewed Sep 19, 2026

View reviewed changes

Dijedon and others added 3 commits September 19, 2026 08:45

test(solid-query): preserve pending mutate callbacks across client sw…

92333f5

…itch

fix(solid-query): retain pending mutation callbacks on client switch

a7fbcca

fix(solid-query): type retained mutation subscription cleanup

0606ea9

TkDodo closed this Sep 19, 2026

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fix(solid-query): follow queryClient changes in useMutation 🤖🤖🤖 - #11545

fix(solid-query): follow queryClient changes in useMutation 🤖🤖🤖#11545
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dijedontahiri:fix/solid-usemutation-queryclient-switch

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