fix(mock): generate tuple values for OpenAPI 3.1 prefixItems (#3697)

Author: wadakatu

packages/mock/src/faker/getters/scalar.ts

@@ -313,6 +313,44 @@ export function getMockScalar({
     }
 
     case 'array': {
+      // OpenAPI 3.1 tuples carry their positional element schemas in
+      // `prefixItems` (not `items`). Mock each fixed position so the emitted
+      // literal is assignable to the generated `[T0, T1, ...]` tuple type.
+      // Emitting only the fixed positions stays type-safe even when `items`
+      // also defines a rest element, because the generated type is
+      // `[...prefix, ...Additional[]]` and the rest permits zero elements.
+      const prefixItems = item.prefixItems as MockSchema[] | undefined;
+      if (prefixItems && prefixItems.length > 0) {
+        const tupleImports: GeneratorImport[] = [];
+        const tupleValues = prefixItems.map((prefixItem, index) => {
+          const { value: elementValue, imports: elementImports } =
+            resolveMockValue({
+              schema: {
+                ...prefixItem,
+                name: item.name,
+                parentName: item.parentName,
+                path: item.path ? `${item.path}.[${index}]` : `#.[${index}]`,
+              },
+              combine,
+              mockOptions,
+              operationId,
+              tags,
+              context,
+              imports,
+              existingReferencedProperties,
+              existingReferencedAllOfRefs,
+              splitMockImplementations,
+            });
+          tupleImports.push(...elementImports);
+          return elementValue;
+        });
+        return {
+          value: `[${tupleValues.join(', ')}]`,
+          imports: tupleImports,
+          name: item.name,
+        };
+      }
+
       if (!item.items) {
         return { value: '[]', imports: [], name: item.name };
       }

tests/__snapshots__/mock/issue-3691/endpoints.ts

@@ -0,0 +1,89 @@
+/**
+ * Generated by orval v8.20.0 🍺
+ * Do not edit manually.
+ * Issue 3691 - tuple prefixItems mock
+ * OpenAPI spec version: 1.0.0
+ */
+import axios from 'axios';
+import type { AxiosInstance, AxiosRequestConfig, AxiosResponse } from 'axios';
+
+import type { Example } from './model';
+
+import { faker } from '@faker-js/faker';
+
+import { HttpResponse, http } from 'msw';
+import type { RequestHandlerOptions } from 'msw';
+
+export const getIssue3691TuplePrefixItemsMock = (
+  axiosInstance: AxiosInstance = axios,
+) => {
+  const getExample = (
+    options?: AxiosRequestConfig,
+  ): Promise<AxiosResponse<Example>> => {
+    return axiosInstance.get(`/example`, options);
+  };
+
+  return { getExample };
+};
+export type GetExampleResult = AxiosResponse<Example>;
+
+export const getGetExampleResponseMock = (
+  overrideResponse: Partial<Extract<Example, object>> = {},
+): Example => ({
+  point: faker.helpers.arrayElement([
+    faker.helpers.arrayElement([
+      [
+        faker.number.float({ fractionDigits: 2 }),
+        faker.number.float({ fractionDigits: 2 }),
+      ],
+      null,
+    ]),
+    undefined,
+  ]),
+  plainPoint: [
+    faker.number.float({ fractionDigits: 2 }),
+    faker.string.alpha({ length: { min: 10, max: 20 } }),
+  ],
+  objTuple: [
+    {
+      id: faker.helpers.arrayElement([
+        faker.string.alpha({ length: { min: 10, max: 20 } }),
+        undefined,
+      ]),
+    },
+    faker.string.alpha({ length: { min: 10, max: 20 } }),
+  ],
+  restTuple: [
+    faker.string.alpha({ length: { min: 10, max: 20 } }),
+    faker.number.float({ fractionDigits: 2 }),
+  ],
+  emptyElemTuple: [faker.string.alpha({ length: { min: 10, max: 20 } }), {}],
+  ...overrideResponse,
+});
+
+export const getGetExampleMockHandler = (
+  overrideResponse?:
+    | Example
+    | ((
+        info: Parameters<Parameters<typeof http.get>[1]>[0],
+      ) => Promise<Example> | Example),
+  options?: RequestHandlerOptions,
+) => {
+  return http.get(
+    '*/example',
+    async (info: Parameters<Parameters<typeof http.get>[1]>[0]) => {
+      return HttpResponse.json(
+        overrideResponse !== undefined
+          ? typeof overrideResponse === 'function'
+            ? await overrideResponse(info)
+            : overrideResponse
+          : getGetExampleResponseMock(),
+        { status: 200 },
+      );
+    },
+    options,
+  );
+};
+export const getIssue3691TuplePrefixItemsMockMock = () => [
+  getGetExampleMockHandler(),
+];

tests/__snapshots__/mock/issue-3691/model/example.ts

@@ -0,0 +1,28 @@
+/**
+ * Generated by orval v8.20.0 🍺
+ * Do not edit manually.
+ * Issue 3691 - tuple prefixItems mock
+ * OpenAPI spec version: 1.0.0
+ */
+import type { ExampleObjTupleItem0 } from './exampleObjTupleItem0';
+
+export interface Example {
+  point?: [number, number] | null;
+  /**
+   * @minItems 2
+   * @maxItems 2
+   */
+  plainPoint: [number, string];
+  /**
+   * @minItems 2
+   * @maxItems 2
+   */
+  objTuple: [ExampleObjTupleItem0, string];
+  /** @minItems 2 */
+  restTuple: [string, number, ...string[]];
+  /**
+   * @minItems 2
+   * @maxItems 2
+   */
+  emptyElemTuple: [string, unknown];
+}

tests/__snapshots__/mock/issue-3691/model/exampleObjTupleItem0.ts

@@ -0,0 +1,10 @@
+/**
+ * Generated by orval v8.20.0 🍺
+ * Do not edit manually.
+ * Issue 3691 - tuple prefixItems mock
+ * OpenAPI spec version: 1.0.0
+ */
+
+export type ExampleObjTupleItem0 = {
+  id?: string;
+};

tests/__snapshots__/mock/issue-3691/model/index.ts

@@ -0,0 +1,9 @@
+/**
+ * Generated by orval v8.20.0 🍺
+ * Do not edit manually.
+ * Issue 3691 - tuple prefixItems mock
+ * OpenAPI spec version: 1.0.0
+ */
+
+export * from './example';
+export * from './exampleObjTupleItem0';

tests/api-generation.spec.ts

@@ -1733,3 +1733,32 @@ test('mock issue-3656 oneOf branch MSW mock imports the enum as a value', async
     /import \{[^}]*\bReasonEnum\b[^}]*\} from '\.\/model'/,
   );
 });
+
+test('mock issue-3691 tuple prefixItems mock values match the generated tuple type', async () => {
+  const content = await readFile(
+    generated('mock', 'issue-3691', 'endpoints.ts'),
+    'utf8',
+  );
+
+  // Each `prefixItems` position must be mocked so the literal is assignable to
+  // the generated tuple type — the old behaviour emitted an empty `[]`.
+  expect(content).not.toContain('plainPoint: []');
+  expect(content).not.toContain('objTuple: []');
+  expect(content).toMatch(
+    /plainPoint: \[\s*faker\.number\.float\([^)]*\),\s*faker\.string\.alpha/,
+  );
+  // Object element keeps its object shape (combine wrapping must not misfire).
+  expect(content).toMatch(/objTuple: \[\s*\{\s*id:/);
+  // `prefixItems` + `items` (tuple-with-rest) emits the fixed positions as a
+  // tuple literal rather than falling through to the `Array.from(...)` path.
+  expect(content).toMatch(
+    /restTuple: \[\s*faker\.string\.alpha\([^)]*\),\s*faker\.number\.float/,
+  );
+  // An empty-schema (`{}`) element must emit a real value (`{}`), never an
+  // empty slot that would produce invalid `[, ...]` output.
+  expect(content).not.toMatch(/emptyElemTuple: \[\s*,/);
+  expect(content).toMatch(/emptyElemTuple: \[\s*faker\.string\.alpha/);
+  // The nullable tuple (`anyOf: [tuple, null]`) is the issue's exact shape and
+  // must not regress to the original empty `[]`.
+  expect(content).not.toContain('point: []');
+});

tests/configs/mock.config.ts

@@ -1085,4 +1085,22 @@ export default defineConfig({
       target: '../specifications/issue-3656.yaml',
     },
   },
+  // Regression for https://github.com/orval-labs/orval/issues/3691:
+  // OpenAPI 3.1 tuples (`prefixItems`) must mock each positional element so
+  // the generated mock is assignable to the generated `[T0, T1, ...]` type.
+  'issue-3691': {
+    output: {
+      target: '../generated/mock/issue-3691/endpoints.ts',
+      schemas: '../generated/mock/issue-3691/model',
+      client: 'axios',
+      mock: {
+        generators: [{ type: 'msw' }],
+      },
+      clean: true,
+      formatter: 'prettier',
+    },
+    input: {
+      target: '../specifications/issue-3691.yaml',
+    },
+  },
 });

tests/specifications/issue-3691.yaml

@@ -0,0 +1,72 @@
+openapi: 3.1.0
+info:
+  title: Issue 3691 - tuple prefixItems mock
+  version: 1.0.0
+paths:
+  /example:
+    get:
+      operationId: getExample
+      responses:
+        '200':
+          description: OK
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Example'
+components:
+  schemas:
+    Example:
+      type: object
+      required:
+        - plainPoint
+        - objTuple
+        - restTuple
+        - emptyElemTuple
+      properties:
+        # Issue's exact shape: optional tuple wrapped in `anyOf: [tuple, null]`.
+        point:
+          anyOf:
+            - type: array
+              prefixItems:
+                - type: number
+                - type: number
+              minItems: 2
+              maxItems: 2
+            - type: 'null'
+        # Plain (non-nullable) tuple isolates the `case 'array'` mock path.
+        plainPoint:
+          type: array
+          prefixItems:
+            - type: number
+            - type: string
+          minItems: 2
+          maxItems: 2
+        # Object element pins the `combine` propagation decision.
+        objTuple:
+          type: array
+          prefixItems:
+            - type: object
+              properties:
+                id:
+                  type: string
+            - type: string
+          minItems: 2
+          maxItems: 2
+        # prefixItems + items: tuple-with-rest stays type-safe with fixed positions only.
+        restTuple:
+          type: array
+          prefixItems:
+            - type: string
+            - type: number
+          items:
+            type: string
+          minItems: 2
+        # Empty-schema (`{}`, i.e. `unknown`) element must emit a real value, not
+        # an empty slot that would break the `[a, b]` literal.
+        emptyElemTuple:
+          type: array
+          prefixItems:
+            - type: string
+            - {}
+          minItems: 2
+          maxItems: 2