fix(query-core): preserve null infinite page params

[gwagjiug]

🎯 Changes

Infinite-query refetches reuse the stored first pageParam, falling back to the current initialPageParam only when no stored value exists. The implementation used ??, so a valid stored null page parameter was treated as missing and replaced when initialPageParam later changed.

• Fall back to initialPageParam only when the stored first page parameter is undefined.
• Add a regression test that fetches with null, changes initialPageParam, and verifies the refetch still uses the stored null value.
• Add a patch changeset for @tanstack/query-core.

Validation: pnpm run test:pr with Node 24.16.0 (209 tasks passed).

✅ 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).

Summary by CodeRabbit

• Bug Fixes
  • Infinite queries now preserve a stored null first-page parameter when refetched, even if a different initial parameter is provided.
  • The initial page parameter is used only when no previous page parameter is stored.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Advanced

Run ID: 29c4ff9b-8712-4396-8017-36938baf2325

📥 Commits

Reviewing files that changed from the base of the PR and between 8a28904 and 90bab86.

📒 Files selected for processing (3)

• .changeset/null-page-param-refetch.md
• packages/query-core/src/__tests__/infiniteQueryBehavior.test.tsx
• packages/query-core/src/infiniteQueryBehavior.ts

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📝 Walkthrough

Walkthrough

The first-page parameter selection now preserves a stored null during infinite-query refetches. A regression test covers refetching with a different initialPageParam, and a patch changeset documents the fix.

Changes

Infinite-query refetch behavior

Layer / File(s)	Summary
Preserve null first page parameter packages/query-core/src/infiniteQueryBehavior.ts, packages/query-core/src/__tests__/infiniteQueryBehavior.test.tsx, .changeset/null-page-param-refetch.md	The first-page selection falls back only when the stored parameter is undefined. The test verifies that null remains in pageParams after refetch. The changeset declares a patch release.

Priority: ⬇️ Low

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

Change: Bug fix

Merge Risk: ⚪ Minimal · up to 90bab

The refetch behavior is covered by the new regression test, with no remaining concrete merge-blocking risk identified.

🚥 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 describes the main change: preserving null infinite-query page parameters during refetch.
Description check	✅ Passed	The description follows the required template, explains the behavior change and motivation, documents the regression test and changeset, and completes the checklist.

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.)

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create a new PR

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