Improve implicit FormData detection. Add tests.

[aphofstede]

Avoid matching "File" type usage too broadly.
Fixes #1538

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Note

Use precise regex matching to detect actual File/binary request bodies as FormData and add tests covering custom formats and false positives.

• Schema Routes (src/schema-routes/schema-routes.ts):
  • Refine implicit FormData detection: replace simple substring check with escaped regex that matches whole File/binary types (including arrays/unions) while avoiding false positives (e.g., FileType).
• Tests (tests/spec/implicitFormData/):
  • Add OpenAPI schema (schema.json), test (basic.test.ts), and snapshot verifying:
    • File/binary properties trigger FormData.
    • Custom formats mapping to non-File types (e.g., FileType) do not.
    • Custom formats mapping to File do.
    • Component names containing "File" do not trigger FormData.

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[smorimoto]

bugbot run

[cursor]

✅ Bugbot reviewed your changes and found no bugs!

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[aphofstede]

You want to merge it @smorimoto?

[Copilot]

Pull request overview

Refines the “implicit FormData detection” workaround so it only triggers for actual File/binary request body types (avoiding false positives like FileType), and adds a dedicated spec fixture to lock in the intended behavior (Fixes #1538).

Changes:

• Tighten implicit FormData detection in SchemaRoutes by replacing a substring check with a more precise regex match.
• Add a new OpenAPI spec fixture and a Vitest snapshot test covering true positives (file/binary) and false positives (custom formats / component names containing File).

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/schema-routes/schema-routes.ts	Updates the implicit FormData detection heuristic to avoid matching File* type names too broadly.
tests/spec/implicitFormData/schema.json	Adds a spec fixture with endpoints exercising file/binary detection and multiple false-positive scenarios.
tests/spec/implicitFormData/basic.test.ts	Adds a snapshot test that generates a client from the fixture and asserts the expected ContentType selection.
tests/spec/implicitFormData/__snapshots__/basic.test.ts.snap	Captures the expected generated output for the new spec test.

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[Copilot]

The regex only matches : File followed by []/|/word-boundary, but it won’t match array types produced as : (File)[] (or : (File | null)[]) because of the leading (. If request bodies can contain arrays of file/binary, the workaround will miss them and keep contentKind as JSON. Consider allowing optional parentheses around the matched type (e.g., match :\s*\(?${type}\)? before handling []/unions), or add a dedicated branch to handle the (...)[] form.

Suggested change

	// Match e.g. ": File" followed by word boundary, array brackets, or union/nullable syntax
	// This prevents false positives like ": FileType" or ": SomeFile"
	// Escape special regex characters (getSchemaType can theoretically return complex types like "File | null" or "UtilRequiredKeys<File, ...>")
	const escapedType = dataType.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
	return new RegExp(`:\\s*${escapedType}(?:\\[\\]|\\s*\\||\\b|$)`).test(
	content,
	);
	// Match e.g. ": File" or ": (File)" (optionally with unions like "(File | null)")
	// followed by word boundary, array brackets, or union/nullable syntax.
	// This prevents false positives like ": FileType" or ": SomeFile".
	// Escape special regex characters (getSchemaType can theoretically return complex types like "File | null" or "UtilRequiredKeys<File, ...>")
	const escapedType = dataType.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
	// Allow either a bare type or a parenthesized form that may contain unions, e.g. "(File | null)".
	const pattern = `:\\s*(?:\\(\\s*${escapedType}(?:\\s*\\|[^)]*)?\\)|${escapedType})(?:\\[\\]|\\s*\\||\\b|$)`;
	return new RegExp(pattern).test(content);