[dinwwwh]

Requested by dinwwwh · project thread

The README promises that a key holding undefined counts as missing, but two checks in the 3.1 to 3.0 converter counted such keys:

• isMediaTypeOnly used Object.keys(value).length === 1, so a Zod-style anyOf branch like { contentMediaType: 'image/png', description: undefined } was not recognized and became a binary string branch instead of being dropped.
• losesRestriction for propertyNames treated { type: 'string', x: undefined } as a lost restriction, so an enclosing oneOf (directly or through a $ref) became anyOf.

Both checks now skip entries holding undefined.

A unit test covers both cases. I also checked that the oRPC document rebuilt with an extra missing: undefined key in every object (the withUndefined twin from #79) converts to 3.0 exactly like the plain one: it fails on main and passes with this change. Once #79 lands, that twin can be extended to 3.0.

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Generated by Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[macroscopeapp]

Approvability

Verdict: Approved at 9ba26e6

Macroscope's review found this PR approvable — This is a small, well-scoped downgrader bug fix that makes two checks consistently treat JavaScript properties holding undefined as missing. The accompanying tests cover both affected conversion paths, with no broader API, infrastructure, or sensitive-data impact.

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[codspeed]

Merging this PR will not alter performance

✅ 21 untouched benchmarks

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_{Comparing claude/project-thread-6ztq09 (9ba26e6) with main (f9427cd)}

[pullfrog]

✅ No new issues found.

Reviewed changes — two checks in the 3.1→3.0 converter now treat keys holding undefined as missing, matching the README contract ("a key holding undefined ... counts as missing"):

• isMediaTypeOnly now ignores undefined-valued siblings (packages/downgrader/src/v3.1-to-v3.0.ts:489). It no longer requires exactly one own key; contentMediaType must be a string and every other entry must hold undefined. A Zod-style branch like { contentMediaType: 'image/png', description: undefined } is now recognized as media-type-only, so the enclosing anyOf is dropped rather than each branch turning into a 3.0 binary string.
• propertyNames restriction check ignores undefined-valued keywords (packages/downgrader/src/v3.1-to-v3.0.ts:367). propertyNames: { type: 'string', description: undefined } no longer counts as a lost restriction, so an enclosing oneOf stays oneOf instead of widening to anyOf.
• Regression test added at packages/downgrader/tests/v3.1-to-v3.0.test.ts:1076, covering both paths.

Both edits are strictly more faithful to the undefined-as-missing contract — a key holding undefined is absent, so the previous pessimistic result was the only divergence, and neither change drops a restriction that should have been kept. I verified the full suite (202 tests) passes on head, and that the new test fails when either source edit is reverted, so this is genuine coverage rather than theatre; uncheck (oxlint/oxfmt/tsc) is clean on both touched files.

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