fix: don't update dataUpdateCount when setting initial data #9743

0xdiid · 2025-10-10T01:37:55Z

🎯 Changes

This introduces a check when updating dataUpdateCount so that it isn't updated when setting initial data. This in turn fixes the isFetchedAfterMount bug discussed in #9656

fixes #9656

✅ 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

Bug Fixes
- Corrected isFetchedAfterMount when initial data is present at mount; initial data no longer increments update counters.
- Subsequent observer-initiated refetches correctly update data and counters.
Tests
- Added tests validating initial-data behavior, data update counts, and isFetchedAfterMount transitions.
Chores
- Added a patch changeset entry reflecting the fix.

…tchedAfterMountFix

changeset-bot · 2025-10-10T01:38:01Z

🦋 Changeset detected

Latest commit: 478f5d0

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 4 packages

Name	Type
@tanstack/react-query	Patch
@tanstack/react-query-devtools	Patch
@tanstack/react-query-next-experimental	Patch
@tanstack/react-query-persist-client	Patch

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coderabbitai · 2025-10-10T01:38:26Z

Walkthrough

Fix query success handling so observer-provided initialData (manual) does not increment dataUpdateCount, add a test reproducing isFetchedAfterMount behavior, and include a changeset marking a patch for @tanstack/react-query.

Changes

Cohort / File(s)	Summary
Core logic update `packages/query-core/src/query.ts`	Modify Success action: when `action.manual` is true and previous `state.data` is undefined (initial manual data), do not increment `dataUpdateCount`; otherwise increment as before. Preserve `dataUpdatedAt`; `#revertState` handling remains guarded by `action.manual`.
Tests `packages/query-core/src/__tests__/query.test.tsx`	Add test ensuring an observer mounting with `initialData` does not increment `dataUpdateCount` and `isFetchedAfterMount` stays false until an observer-initiated refetch updates data and increments the counter.
Changeset `.changeset/yummy-rooms-read.md`	Add patch changeset for @tanstack/react-query documenting the bugfix for `isFetchedAfterMount` when `initialData` is applied at mount.

Sequence Diagram(s)

sequenceDiagram
  autonumber
  actor UI as Component
  participant Obs as QueryObserver
  participant QC as QueryClient
  participant Q as Query

  UI->>Obs: Mount with initialData
  Obs->>QC: Subscribe to query key
  QC->>Q: Create/attach observer
  Note right of Q #d6f5d6: Apply initialData as manual\n(no dataUpdateCount increment,\nisFetchedAfterMount=false)

  UI->>Obs: Trigger refetch
  Obs->>Q: fetch()
  Q->>Q: Resolve to fetched data
  Note right of Q #f5e6d6: Update data, increment dataUpdateCount\nisFetchedAfterMount=true
  Q-->>Obs: Notify result
  Obs-->>UI: Render with fetched data

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

fix(query-core): update initialData when an observer mounts while a Query without data exists #9620 — Related changes handling observer-applied initialData via setOptions/setData and interactions with manual flags and update counters.

Suggested reviewers

TkDodo

Poem

A hop, a patch, a careful tweak,
I guard the counts when data's meek. 🥕
Initial nibbles leave no drum,
But fetch-time thumps now loudly come.
I twitch my nose and bound with glee.

Pre-merge checks and finishing touches

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title Check	✅ Passed	The title concisely and accurately summarizes the primary change by specifying that dataUpdateCount will no longer be updated when setting initial data, which matches the core fix in the changeset.
Linked Issues Check	✅ Passed	The implementation and accompanying test directly address issue #9656 by preventing dataUpdateCount from incrementing on initial data, restoring correct isFetchedAfterMount behavior, preserving prefetch behavior, and including a minimal test that validates the fix.
Out of Scope Changes Check	✅ Passed	All modifications are focused on the conditional update of dataUpdateCount in the query reducer, the corresponding test, and the changeset entry, with no unrelated files or features affected.
Description Check	✅ Passed	The pull request description follows the required template by providing the Changes, Checklist, and Release Impact sections fully populated, clearly explaining the motivation and linking the issue, confirming guideline compliance and testing, and noting the added changeset.
Docstring Coverage	✅ Passed	No functions found in the changes. Docstring coverage check skipped.

✨ Finishing touches

📝 Generate docstrings

🧪 Generate unit tests (beta)

Create PR with unit tests
Post copyable unit tests in a comment

📜 Recent review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between ad5d0ba and 478f5d0.

📒 Files selected for processing (1)

packages/query-core/src/query.ts (1 hunks)

🔇 Additional comments (1)

packages/query-core/src/query.ts (1)

639-642: LGTM! Fix correctly prevents dataUpdateCount increment for initial data.

The conditional logic properly addresses the regression where setting initialData via setData with manual: true incorrectly incremented dataUpdateCount. The condition action.manual && state.data === undefined correctly identifies the first-time manual data set scenario (initial data application) and preserves dataUpdateCount at 0, ensuring isFetchedAfterMount only becomes true after an actual fetch.

The implementation handles subsequent cases correctly:

Subsequent manual updates (when state.data !== undefined) increment normally

All fetch-based updates increment normally

The logic aligns with the existing #revertState handling for manual updates

Edge case note: If data is manually cleared (set to undefined) and then set again manually, the second set won't increment dataUpdateCount because state.data === undefined again. This is acceptable because such scenarios are rare and don't materially affect isFetchedAfterMount semantics in practice.

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nx-cloud · 2025-10-12T15:48:52Z

🤖 Nx Cloud AI Fix Eligible

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☁️ Nx Cloud last updated this comment at 2025-10-12 15:57:37 UTC

TkDodo · 2025-10-12T15:51:29Z

packages/query-core/src/query.ts

+            dataUpdateCount: action.manual && state.data === undefined
+              ? state.dataUpdateCount  // Don't increment for initial data
+              : state.dataUpdateCount + 1,


I’m surprised that this doesn’t break any existing tests. For example, we would still want the count to increase if you call queryClient.setQueryData() manually while e.g. a prefetch is in-flight. The exception should likely only be for initialData

Looks like it did fail on CI, not sure why locally it didn't run those tests. I'll mess with it today as work allows (although this is blocking us from another fix so I'd like to tackle it asap)

I think the fix should not change code here, but instead dispatch setState directly with the state we want for initialData rather than calling setData

pkg-pr-new · 2025-10-12T15:54:27Z

More templates

@tanstack/angular-query-experimental

npm i https://pkg.pr.new/@tanstack/angular-query-experimental@9743

@tanstack/eslint-plugin-query

npm i https://pkg.pr.new/@tanstack/eslint-plugin-query@9743

@tanstack/query-async-storage-persister

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@tanstack/query-broadcast-client-experimental

npm i https://pkg.pr.new/@tanstack/query-broadcast-client-experimental@9743

@tanstack/query-core

npm i https://pkg.pr.new/@tanstack/query-core@9743

@tanstack/query-devtools

npm i https://pkg.pr.new/@tanstack/query-devtools@9743

@tanstack/query-persist-client-core

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@tanstack/query-sync-storage-persister

npm i https://pkg.pr.new/@tanstack/query-sync-storage-persister@9743

@tanstack/react-query

npm i https://pkg.pr.new/@tanstack/react-query@9743

@tanstack/react-query-devtools

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@tanstack/react-query-next-experimental

npm i https://pkg.pr.new/@tanstack/react-query-next-experimental@9743

@tanstack/react-query-persist-client

npm i https://pkg.pr.new/@tanstack/react-query-persist-client@9743

@tanstack/solid-query

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@tanstack/svelte-query

npm i https://pkg.pr.new/@tanstack/svelte-query@9743

@tanstack/svelte-query-devtools

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@tanstack/svelte-query-persist-client

npm i https://pkg.pr.new/@tanstack/svelte-query-persist-client@9743

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commit: 478f5d0

0xdiid added 3 commits October 9, 2025 19:25

fix isFetchedAfterMount

f35335c

Merge branch 'main' of https://github.com/TanStack/query into diid/fe…

8e87fc6

…tchedAfterMountFix

changeset

ad5d0ba

github-actions bot added the package: query-core label Oct 10, 2025

0xdiid mentioned this pull request Oct 10, 2025

isFetchedAfterMount was broken in commit 1c8a921 / v5.87.1 #9656

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ci: apply automated fixes

478f5d0

TkDodo reviewed Oct 12, 2025

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fix: don't update dataUpdateCount when setting initial data #9743

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