[dinwwwh]

Requested by dinwwwh · project thread

Test-only. Stryker on main left mutants alive in the checks #87/#88 added to the 3.1 to 3.0 nullable merge. This adds expectations to the existing tests in tests/v3.1-to-v3.0.test.ts; main already gives the right output for each one.

• anyOf of a $ref to a type: "null" target and null stays anyOf. This covers rejectsNull letting "null" through.
• anyOf of a $ref to a type: ["object", "string"] target and null becomes oneOf. This covers the array type case of rejectsNull.
• A typed branch with oneOf beside null is not merged and becomes a oneOf pair. This covers oneOf in NOT_NULLABLE_KEYWORDS.
• A null branch with a description is not treated as only null, so the anyOf stays as it is. This covers the key count in isOnlyNullSchema.

I applied each of those four mutations by hand. All of them pass the tests on main and fail with this change.

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Generated by Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[codspeed]

Merging this PR will not alter performance

✅ 21 untouched benchmarks

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_{Comparing claude/project-thread-luckgz (f04c471) with main (8ad5613)}

[pullfrog]

✅ No new issues found.

Reviewed changes — test-only addition to the 3.1→3.0 behavior suite; no source changes.

• oneOf branch guard — adds { type: 'string', oneOf: [...] } to the typed branch loop, pinning that oneOf in NOT_NULLABLE_KEYWORDS keeps the pair as oneOf instead of merging to nullable.
• Non-trivial null branch — asserts { type: 'null', description: 'd' } is not treated as only-null, so the anyOf stays put (covers the key count in isOnlyNullSchema).
• Array type rejects null — adds pet({ type: ['object', 'string'] }) expecting oneOf; this is the only test exercising that an array type without "null" rejects null.
• type: 'null' does not reject — adds pet({ type: 'null' }) expecting the pair to stay anyOf.

I verified the coverage is not theater: all 84 tests pass, uncheck (oxlint/oxfmt/tsc) is clean on the changed file, and hand-applying each of the four claimed mutations to packages/downgrader/src/v3.1-to-v3.0.ts makes the corresponding new expectation fail (removing 'oneOf' from NOT_NULLABLE_KEYWORDS; widening isOnlyNullSchema's length === 3 to >= 3; forcing the rejectsNull array branch to reject nothing; dropping && type !== 'null' from the string branch). The source was restored — working tree is clean.

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