[milamer]

Adds src/__tests__/types.test-d.ts: expectTypeOf assertions for the public API, checked by npm run typecheck (tsconfig includes src). No change to src/ or the package; test: doesn't release.

What is covered

• parseFormData
  • parameter 0 is Iterable<[path: string, value: string | File]>, parameter 1 is ParseFormDataOptions | undefined
  • accepts FormData, URLSearchParams, [['a', 'x']], and entries with a native File value
  • rejects entries with a number or Blob value (@ts-expect-error)
  • returns an object of JSON values and Files
• ParseFormDataOptions: exact type (removeEmptyString, depth, transformEntry(entry, defaultTransform) => {path, value}), and a transformEntry that calls defaultTransform compiles
• A transformEntry that returns a Date must not compile (@ts-expect-error). This is the known limitation behind [Feature request]: Add date-string to date parsing flag #3; if a later change allows it, this test fails and has to be updated on purpose.
• Every error class (DuplicateKeyError, MixedArrayError, ForbiddenKeyError, DepthLimitError, InvalidPathError): constructor takes [key: string], extends Error, key: string, name: string

The expected types are written out in the test file instead of imported from src/types.ts, so a change to the exported types fails the tests.

Config change: vitest.config.mts

vitest's include (src/**/__tests__/**/*.ts) matched the new file and ran it as 13 runtime tests. At runtime every expectTypeOf call is a no-op, so those tests always pass without checking anything. The file is now excluded (src/**/*.test-d.ts); vitest's typecheck mode isn't needed because tsc already checks it.

No other config changes needed:

• knip: its vitest plugin already treats *.test-d.ts as entry files, so the file isn't reported.
• coverage: src/**/__tests__/** is already excluded.
• oxlint: expectTypeOf is already in vitest/expect-expect's assertFunctionNames.

Checked that the tests can fail

Temporarily changed src/ (then restored) and ran npm run typecheck:

• depth?: number | string in ParseFormDataOptions → the options test fails
• | Date added to JsonValue → the return type test fails and the Date @ts-expect-error becomes unused
• key: string | number in DuplicateKeyError → its key test fails

Also, replacing the rejected number value with a string makes its @ts-expect-error unused, so the rejection tests aren't passing for an unrelated reason.

npm run validate passes.

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (cd88e9e) to head (59c8818).
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Additional details and impacted files

@@            Coverage Diff            @@
##              main       #16   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            4         4           
  Lines          134       134           
  Branches        45        45           
=========================================
  Hits           134       134           

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