fix(query-core): shallowEqualObjects ignores key-set differences when counts match

[francisjohnjohnston-web]

What

shallowEqualObjects now returns false when two objects have the same number of keys but different key names (e.g. { a: 1, b: undefined } vs { a: 1, c: undefined }).

Why

The function only iterated over a's keys and compared a[key] !== b[key]. A key present on a but missing from b reads as undefined on b; if a's value for that key is also undefined (or otherwise equal), the objects compared as equal despite having different key sets — violating the documented "shallow compare objects" contract. Real call site: QueryObserver.setOptions gates the observerOptionsUpdated notification with this comparison, so swapping one defaulted option key for another between renders could silently suppress that notification.

Safety

Pure utility change; an additive own-property guard. No existing test asserted the old (incorrect) behaviour. Result-object comparisons (which use fixed-shape objects) are unaffected, so there is no behavioural or performance regression for the common path.

Testing

Added should return 'false' for same-length objects with different keys to utils.test.tsx: it fails on the current code (expected true to deeply equal false) and passes after the fix. Full query-core runtime suite green (480/480), typecheck clean.

Impact

Tighter, contract-correct shallow equality — restores correct change-detection for option updates that swap keys without changing key count.

Summary by CodeRabbit

• Bug Fixes
  • Fixed object comparison logic to correctly identify differences when objects contain different properties, improving accuracy of equality checks.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 91e0aabc-94f6-454c-9546-429445832255

📥 Commits

Reviewing files that changed from the base of the PR and between 3042860 and 1323720.

📒 Files selected for processing (2)

• packages/query-core/src/__tests__/utils.test.tsx
• packages/query-core/src/utils.ts

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📝 Walkthrough

Walkthrough

This PR fixes shallowEqualObjects to properly validate own-property ownership before comparing values. The implementation adds an own-property guard check, and a corresponding test ensures objects with different key sets are correctly identified as unequal.

Changes

Own-property shallow equality validation

Layer / File(s)	Summary
shallowEqualObjects own-property guard and validation packages/query-core/src/utils.ts, packages/query-core/src/__tests__/utils.test.tsx	shallowEqualObjects now calls hasOwn.call(b, key) when iterating keys from a, preventing false equality when keys are inherited. New test case verifies that same-length objects with different key sets (including undefined values) return false.

🎯 2 (Simple) | ⏱️ ~8 minutes

Suggested reviewers

• TkDodo

🐰 A shallow check grows deep today,
Own properties guard the way!
Keys must match from prop to prop,
No inherited tricks will stop
This equality's honest say.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 inconclusive)

Check name	Status	Explanation	Resolution
Description check	❓ Inconclusive	The description comprehensively covers What, Why, Safety, Testing, and Impact, but does not follow the required template structure with the specified checklist items.	Restructure the description to follow the template with explicit 'Changes' section, 'Checklist' items, and 'Release Impact' section indicating whether a changeset was generated.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main fix: shallowEqualObjects now correctly handles objects with matching key counts but different key names.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
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.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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