[dinwwwh]

Requested by dinwwwh · project thread

Test-only. Stryker on packages/downgrader/src left 155 of 1,211 mutants alive on main. With these tests, 81 are left, and no mutant survives that was killed before.

What the new cases cover

3.1 to 3.0

• A schema using every keyword 3.0 shares (readOnly, writeOnly, deprecated, discriminator, externalDocs, xml, multipleOf, min/maxProperties, and the rest) comes out unchanged, not renamed to x-.
• it.each over every in-place applicator beside unevaluatedProperties: false: none of them turns it into additionalProperties: false.
• Exclusive bounds as a table: each bound alone, the plain bound stricter, the exclusive bound stricter, and both equal.
• Tuple bounds as a table, including ArkType's { prefixItems: [a, b], minItems: 1, items: false }, which gets maxItems: 2.
• $dynamicRef and $vocabulary are dropped.
• $ref pointers decode percent-encoding, ~1, and ~0 in that order, and non-pointer or inherited-key refs stay as written.
• Extensions in paths, responses, and callbacks are copied as they are.

3.2 to 3.1

• it.each over every subschema keyword, map keyword, and list keyword: xml.nodeType converts inside each one. nodeType: none on an array doesn't set wrapped.
• Extensions in paths, responses, and callbacks are copied as they are. A Link's server is compared exactly.

Shared helpers

• Own __proto__ keys stay ordinary, writable, enumerable keys.
• Keys holding undefined are compared with toStrictEqual, so a missing key and one holding undefined count as different.
• Cycles through arrays stay cycles.
• An Object.create(null) schema is read like any other object.

README input promises (orpc.test.ts)

• The oRPC document converts to 3.1 the same when it's built from null-prototype objects or has a key holding undefined in every object. It also converts to 3.0 the same when built from null-prototype objects.
• The undefined twin is not yet checked for the 3.1-to-3.0 step, because that step fails today. isMediaTypeOnly and the propertyNames check count keys that hold undefined. That bug is left for its own fix PR, which can add the check.

Remaining survivors

Most of the 81 that are left are equivalent mutants (the $ref target cache, clone's pre-check, typeof guards that only matter for malformed input). A few are .map(() => undefined) mutants that throw at import, which Stryker records as surviving. The rest are in the looseness and type logic, which this PR doesn't touch.

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Generated by Claude Code

[macroscopeapp]

Approvability

Verdict: Approved at 0165644

Macroscope's review found this PR approvable — This PR only expands downgrader test coverage for mutation survivors and unusual object/input shapes; it does not modify production converter code or shipped behavior. The changed files run only in the test harness.

Notes:

• No code objects were reviewed. Approvability was decided on eligibility alone.

^{You can add or adjust custom eligibility rules. Learn more.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[codspeed]

Merging this PR will not alter performance

✅ 21 untouched benchmarks

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_{Comparing claude/project-thread-k95hv1 (0165644) with main (f9427cd)}

[pullfrog]

✅ No new issues found.

Reviewed changes

This run reviewed the full test-only diff at 0165644 (3 files). I ran the three touched test files (133 passed) and traced each new expectation against src/v3.1-to-v3.0.ts and src/v3.2-to-v3.1.ts.

• 3.1→3.0 schema tables — "keeps every keyword 3.0 shares as it is"; exclusive bounds as an it.each (adds the equal-bound rows); tuple bounds as a table (items: false → maxItems, ArkType { prefixItems, minItems, items: false } → maxItems: 2); $dynamicRef/$vocabulary dropped; pointer percent/~1/~0 decode order; non-pointer and inherited-key $refs left as written; unevaluatedProperties beside each IN_PLACE_APPLICATORS entry stays out of additionalProperties; extensions copied as-is; a non-string $ref becomes {}.
• 3.2→3.1 schema/keyword coverage — xml.nodeType converted inside every subschema/map/list keyword, nodeType: 'none' sets no wrapped, exact Link server and dropped content $ref, own __proto__ keys kept ordinary, toStrictEqual for undefined-holding keys, cycles through arrays preserved.
• oRPC input promises — the document converts identically when rebuilt from null-prototype objects and from objects carrying missing: undefined (3.2→3.1), and from null-prototype objects for the 3.1→3.0 step.

Every expectation is consistent with the implementation. The keyword it.each tables mirror the source lists (SUBSCHEMA_KEYWORDS, IN_PLACE_APPLICATORS, SUBSCHEMA_MAP/LIST_KEYWORDS, the $ref-rewrite set), so coverage tracks the code rather than hard-coding arbitrary cases. The author's note that the undefined twin is not asserted for 3.1→3.0 is a pre-existing isMediaTypeOnly/propertyNames bug left for a separate fix PR — out of scope here.

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