fix(preact-query): retry on mount for falsy errors when throwOnError returns false

[S-jooyoung]

🎯 Changes

Ports #11328 (react-query) to preact-query.

Summary

ensurePreventErrorBoundaryRetry in preact-query has the same check as the one fixed for react-query in #11328: a function-valued throwOnError was only evaluated when query.state.error was truthy. For a query that rejected with a falsy value (e.g. Promise.reject() / undefined), the callback was skipped, the function itself was treated as truthy, and retryOnMount was disabled even though throwOnError would have returned false. This is the preact side of #11327.

Changes

• packages/preact-query/src/errorBoundaryUtils.ts: check query.state.status === 'error' instead of the truthiness of query.state.error, so the throwOnError callback runs for every failed query.
• packages/preact-query/src/__tests__/useQuery.test.tsx: regression test — a query that rejects with undefined, throwOnError: () => false, retryOnMount: () => true must refetch on remount (queryFn called twice).
• changeset (@tanstack/preact-query patch).

Test plan

• The new test fails on main (expected "vi.fn()" to be called 2 times, but got 1 times) and passes with the fix.
• pnpm nx run @tanstack/preact-query:test:lib — 529 passed.
• pnpm run test:pr --base=upstream/main for the affected projects.

✅ Checklist

• I have followed the steps in the Contributing guide.
• I have tested code changes locally with pnpm run test:pr, or these tests do not apply to this pull request.
• I fully understand the code in this pull request, including any code generated with AI assistance.

🚀 Release Impact

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

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📥 Commits

Reviewing files that changed from the base of the PR and between fe77cdc and d3a920b.

📒 Files selected for processing (3)

• .changeset/preact-falsy-error-retry-on-mount.md
• packages/preact-query/src/__tests__/useQuery.test.tsx
• packages/preact-query/src/errorBoundaryUtils.ts

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📝 Walkthrough

Walkthrough

Preact Query now evaluates function-valued throwOnError for error states, including falsy errors. A regression test covers retry on remount, and a patch changeset documents the behavior.

Changes

Preact falsy-error retry handling

Layer / File(s)	Summary
Error-boundary retry behavior packages/preact-query/src/errorBoundaryUtils.ts, packages/preact-query/src/__tests__/useQuery.test.tsx, .changeset/preact-falsy-error-retry-on-mount.md	ensurePreventErrorBoundaryRetry evaluates throwOnError when the query status is error and passes the query error and query instance to the handler. The regression test verifies retry after remount for a falsy error. The changeset records the patch release.
Estimated code review effort: 2 (Simple)	~10 minutes

Merge Risk: ⚪ Minimal · up to d3a92

Preact Query now evaluates function-valued throwOnError callbacks for failed queries even when the rejection value is falsy, allowing configured remount retries. The change includes targeted regression coverage and is ready to merge.

Suggested reviewers: tkdodo

🚥 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%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 2 files. (1 skipped: 1 …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly and concisely describes the primary fix: enabling retry on mount for falsy errors when throwOnError returns false.
Description check	✅ Passed	The description follows the repository template. It explains the motivation, lists the affected files and behavior, documents testing, and completes the checklist and release impact sections.

Full details: Docstring Coverage

Explanation

Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 2 files. (1 skipped: 1 unsupported.)

• Fix all pre-merge checks with AI

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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