fix(openapi3): emit uniqueItems on operation parameter schemas

[dschmidt]

@JsonSchema.uniqueItems is currently a no-op when applied to query, path or header parameters in @typespec/openapi3. The body schema-emitter applies it via applyConstraint(jsonSchemaModule.getUniqueItems, ...) in schema-emitter.ts, but parameter schemas go through applyIntrinsicDecorators in openapi.ts, which never consulted the optional jsonSchemaModule. Arrays declared inline on operation parameters therefore lost the constraint between source TypeSpec and the emitted OpenAPI.

op listUsers(
  @query
  @JsonSchema.uniqueItems
  `$select`?: ("id" | "displayName")[],
): User[];

Before this PR the emitted schema for $select was { type: array, items: { ... } }. After, it is { type: array, uniqueItems: true, items: { ... } } — which matters in practice because the openapi-generator typescript-axios template renders that as Set<EnumX> instead of Array<EnumX>.

The same patch also tightens the useStateMap generic for uniqueItems in @typespec/json-schema from the implicit unknown to boolean, matching every other state-backed decorator in the compiler so the openapi3 emitter can consume getUniqueItems without a cast.

[dschmidt]

@microsoft-github-policy-service agree

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commit: c8a9565

[github-actions]

All changed packages have been documented.

• ✅ @typespec/json-schema
• ✅ @typespec/openapi3

Show changes

@typespec/openapi3 - fix ✏️

Propagate @JsonSchema.uniqueItems to query, path and header parameter schemas. The decorator was only applied to body model property schemas; for HTTP parameter schemas (which go through applyIntrinsicDecorators) it was silently dropped, so arrays declared on operation parameters never emitted uniqueItems: true even when the decorator was present.,> ,> tsp,> op listUsers(,> @query,> @JsonSchema.uniqueItems,> $select?: ("id" | "displayName")[],,> ): User[];,>

@typespec/json-schema - internal ✏️

Add the explicit <Type, boolean> generic to the useStateMap call backing @uniqueItems, matching the convention used by every other state-backed decorator in the compiler. This makes getUniqueItems return boolean | undefined rather than unknown | undefined and lets downstream emitters consume the value without a cast.

[timotheeguerin]

Thanks for the contribution