fix: @opExample generation with @versioned namespaces, unions, and enums

.chronus/changes/fixes-opeanapi3-versioned-examples-2025-11-24-10-46-23.md

@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@typespec/openapi3"
+---
+
+Fixed examples generation for operations with unions and nested enums for versioned services

packages/openapi3/src/examples.ts

@@ -266,7 +266,10 @@ export function getExampleOrExamples(
   ) {
     const [example, type] = examples[0];
     const encodeAs = getEncodeAs(program, type);
-    return { example: serializeValueAsJson(program, example.value, type, encodeAs) };
+    const exactValueType = program.checker.getValueExactType(example.value);
+    return {
+      example: serializeValueAsJson(program, example.value, exactValueType ?? type, encodeAs),
+    };
   } else {
     const exampleObj: Record<string, OpenAPI3Example> = {};
     for (const [index, [example, type]] of examples.entries()) {

packages/openapi3/test/examples.test.ts

@@ -962,4 +962,43 @@ worksFor(supportedVersions, ({ openApiFor }) => {
       "2021-01-01T00:00:00Z",
     );
   });
+
+  it("supports example generation for union that contains enums", async () => {
+    const res = await openApiFor(
+      `
+      @service
+      namespace MyService {
+        enum Enum {
+          a: "a",
+          b: "b",
+        }
+
+        model Foo {
+          entityType: "foo";
+        }
+
+        model Bar {
+          entityType: "bar";
+          enumValue: Enum;
+        }
+
+        @opExample(#{ returnType: #[#{ entityType: "bar", enumValue: Enum.a }] })
+        op testOp(): (Foo | Bar)[];
+      }
+    `,
+    );
+
+    ok(res.components?.schemas);
+    ok(res.paths["/"].get);
+    ok(res.paths["/"].get.responses);
+    ok("200" in res.paths["/"].get.responses);
+    ok("content" in res.paths["/"].get.responses["200"]);
+    ok(res.paths["/"].get.responses["200"].content);
+    expect(res.paths["/"].get?.responses["200"].content["application/json"].example).toEqual([
+      {
+        entityType: "bar",
+        enumValue: "a",
+      },
+    ]);
+  });
 });

packages/openapi3/test/versioning.test.ts

@@ -217,5 +217,53 @@ worksFor(supportedVersions, ({ openApiFor, version: specVersion }) => {
     `,
       );
     });
+
+    it("supports example generation for union that contains enums", async () => {
+      const { v1 } = await openApiForVersions(
+        `        
+      namespace MyService {
+        enum Versions {
+          v1
+        }
+      }
+
+      @versioned(Versions)
+      @service
+      namespace MyService {
+        enum Enum {
+          a: "a",
+          b: "b",
+        }
+
+        model Foo {
+          entityType: "foo";
+        }
+
+        model Bar {
+          entityType: "bar";
+          enumValue: Enum;
+        }
+
+        @opExample(#{ returnType: #[#{ entityType: "bar", enumValue: Enum.a }] })
+        op testOp(): (Foo | Bar)[];
+      }
+    `,
+        ["v1"],
+      );
+
+      strictEqual(v1.info.version, "v1");
+      ok(v1.components?.schemas);
+      ok(v1.paths["/"].get);
+      ok(v1.paths["/"].get.responses);
+      ok("200" in v1.paths["/"].get.responses);
+      ok("content" in v1.paths["/"].get.responses["200"]);
+      ok(v1.paths["/"].get.responses["200"].content);
+      deepStrictEqual(v1.paths["/"].get?.responses["200"].content["application/json"].example, [
+        {
+          entityType: "bar",
+          enumValue: "a",
+        },
+      ]);
+    });
   });
 });