Fix when rendering version enum only include current member and mark it modelAsString: true

.chronus/changes/fix-emit-api-version-2024-4-25-9-53-10.md

@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@azure-tools/typespec-autorest"
+---
+
+When emitting version enum only include current version and mark with `modelAsString: true`

packages/samples/test/output/core/versioning/@azure-tools/typespec-autorest/v1/openapi.json

@@ -121,12 +121,17 @@
       "required": true,
       "type": "string",
       "enum": [
-        "v1",
-        "v2"
+        "v1"
       ],
       "x-ms-enum": {
         "name": "Versions",
-        "modelAsString": false
+        "modelAsString": true,
+        "values": [
+          {
+            "name": "v1",
+            "value": "v1"
+          }
+        ]
       },
       "x-ms-parameter-location": "method",
       "x-ms-client-name": "apiVersion"

packages/samples/test/output/core/versioning/@azure-tools/typespec-autorest/v2/openapi.json

@@ -149,12 +149,17 @@
       "required": true,
       "type": "string",
       "enum": [
-        "v1",
         "v2"
       ],
       "x-ms-enum": {
         "name": "Versions",
-        "modelAsString": false
+        "modelAsString": true,
+        "values": [
+          {
+            "name": "v2",
+            "value": "v2"
+          }
+        ]
       },
       "x-ms-parameter-location": "method",
       "x-ms-client-name": "apiVersion"

packages/typespec-autorest/src/openapi.ts

@@ -1259,14 +1259,14 @@ export async function getOpenAPIForService(
       }
       return false;
     }
+  }
 
-    function isVersionEnum(program: Program, enumObj: Enum): boolean {
-      const [_, map] = getVersionsForEnum(program, enumObj);
-      if (map !== undefined && map.getVersions()[0].enumMember.enum === enumObj) {
-        return true;
-      }
-      return false;
+  function isVersionEnum(program: Program, enumObj: Enum): boolean {
+    const [_, map] = getVersionsForEnum(program, enumObj);
+    if (map !== undefined && map.getVersions()[0].enumMember.enum === enumObj) {
+      return true;
     }
+    return false;
   }
 
   function emitTags() {
@@ -1322,6 +1322,34 @@ export async function getOpenAPIForService(
     return {};
   }
 
+  /**
+   * Version enum is special so we we just render the current version with modelAsString: true
+   */
+  function getSchemaForVersionEnum(e: Enum, currentVersion: string): OpenAPI2Schema {
+    const member = [...e.members.values()].find((x) => (x.value ?? x.name) === currentVersion);
+    compilerAssert(
+      member,
+      `Version enum ${e.name} does not have a member for ${currentVersion}.`,
+      e
+    );
+    return {
+      type: "string",
+      description: getDoc(program, e),
+      enum: [member.value ?? member.name],
+      "x-ms-enum": {
+        name: e.name,
+        modelAsString: true,
+        values: [
+          {
+            name: member.name,
+            value: member.value ?? member.name,
+            description: getDoc(program, member),
+          },
+        ],
+      },
+    };
+  }
+
   function getSchemaForEnum(e: Enum): OpenAPI2Schema {
     const values = [];
     if (e.members.size === 0) {
@@ -1338,6 +1366,10 @@ export async function getOpenAPIForService(
       }
     }
 
+    // If we are rendering a specific version and trying to render the version enum we should treat it specially to only include the current version.
+    if (isVersionEnum(program, e) && context.version) {
+      return getSchemaForVersionEnum(e, context.version);
+    }
     const schema: OpenAPI2Schema = { type, description: getDoc(program, e) };
     if (values.length > 0) {
       schema.enum = values;

packages/typespec-autorest/test/versioning.test.ts

@@ -1,8 +1,66 @@
 import { deepStrictEqual, strictEqual } from "assert";
-import { describe, it } from "vitest";
+import { describe, expect, it } from "vitest";
+import { OpenAPI2Document } from "../src/openapi2-document.js";
 import { openApiFor } from "./test-host.js";
 
 describe("typespec-autorest: versioning", () => {
+  it("if version enum is referenced only include current member and mark it with modelAsString: true", async () => {
+    const { v1, v2 } = (await openApiFor(
+      `
+      @service
+      @versioned(Versions)
+      @server(
+        "https://example.com/{apiVersion}",
+        "Doc",
+        {
+          @path apiVersion: Versions,
+        }
+      )
+      namespace MyService {
+        enum Versions {
+          v1,
+          v2,
+        }
+      }
+    `,
+      ["v1", "v2"]
+    )) as { v1: OpenAPI2Document; v2: OpenAPI2Document };
+    expect(v1["x-ms-parameterized-host"]?.parameters?.[0]).toEqual({
+      enum: ["v1"],
+      in: "path",
+      name: "apiVersion",
+      required: true,
+      type: "string",
+      "x-ms-enum": {
+        modelAsString: true,
+        name: "Versions",
+        values: [
+          {
+            name: "v1",
+            value: "v1",
+          },
+        ],
+      },
+    });
+    expect(v2["x-ms-parameterized-host"]?.parameters?.[0]).toEqual({
+      enum: ["v2"],
+      in: "path",
+      name: "apiVersion",
+      required: true,
+      type: "string",
+      "x-ms-enum": {
+        modelAsString: true,
+        name: "Versions",
+        values: [
+          {
+            name: "v2",
+            value: "v2",
+          },
+        ],
+      },
+    });
+  });
+
   it("works with models", async () => {
     const { v1, v2, v3 } = await openApiFor(
       `