feat(tcgc): add isPreview to SdkPackageType metadata

.chronus/changes/tcgc-add-ispreview-to-metadata-2026-7-27-15-15-0.md

@@ -0,0 +1,7 @@
+---
+changeKind: feature
+packages:
+  - "@azure-tools/typespec-client-generator-core"
+---
+
+Add `isPreview` boolean to `SdkPackageType.metadata` to indicate whether the SDK targets any preview API versions.

packages/typespec-client-generator-core/src/interfaces.ts

@@ -1371,6 +1371,13 @@ export interface SdkPackage<TServiceOperation extends SdkServiceOperation> {
      * If value is a string, the service is versioned with the specified version.
      */
     apiVersions?: Map<string, string>;
+    /**
+     * Whether the package targets any preview API versions.
+     * `true` if any targeted API version has the `@previewVersion` decorator or matches the preview string regex.
+     * `false` if all versions are stable.
+     * `undefined` if no versioning is present.
+     */
+    isPreview?: boolean;
   };
 }
 

packages/typespec-client-generator-core/src/package.ts

@@ -4,6 +4,7 @@ import {
   getNamespaceFullName,
   ignoreDiagnostics,
 } from "@typespec/compiler";
+import { isPreviewVersion } from "@azure-tools/typespec-azure-core";
 
 import { prepareClientAndOperationCache } from "./cache.js";
 import { createSdkClientType } from "./clients.js";
@@ -72,6 +73,7 @@ export async function createSdkPackage<TServiceOperation extends SdkServiceOpera
             ? [...versions.values()][0].at(-1)
             : undefined,
       apiVersions: apiVersionsMap,
+      isPreview: computeIsPreview(context, versions),
     },
   };
   organizeNamespaces(context, sdkPackage);
@@ -202,3 +204,26 @@ async function computeCrossLanguageVersion(context: TCGCContext): Promise<string
   const hex = hashArray.map((b) => b.toString(16).padStart(2, "0")).join("");
   return hex.substring(0, 12);
 }
+
+function computeIsPreview(
+  context: TCGCContext,
+  versions: Map<unknown, string[]>,
+): boolean | undefined {
+  const allVersions = [...versions.values()].flat();
+  if (allVersions.length === 0) {
+    return undefined;
+  }
+
+  // First check @previewVersion decorator on enum members
+  for (const versionEnum of context.getPackageVersionEnum().values()) {
+    if (!versionEnum) continue;
+    for (const member of versionEnum.members.values()) {
+      if (isPreviewVersion(context.program, member)) {
+        return true;
+      }
+    }
+  }
+
+  // Fall back to regex check for backward compatibility
+  return allVersions.some((v) => context.previewStringRegex.test(v));
+}

packages/typespec-client-generator-core/test/package/versioning.test.ts

@@ -1525,3 +1525,87 @@ it("multi-service client has no versionsEnum", async () => {
   ok(biClient.versionsEnum);
   strictEqual(biClient.versionsEnum.name, "VersionsB");
 });
+
+it("isPreview is false for stable versions", async () => {
+  const { program } = await SimpleTester.compile(`
+    @service
+    @versioned(Versions)
+    namespace TestService;
+    enum Versions {
+      v1,
+      v2,
+      v3,
+    }
+    op test(): void;
+  `);
+
+  const context = await createSdkContextForTester(program);
+  const sdkPackage = context.sdkPackage;
+  strictEqual(sdkPackage.metadata.isPreview, false);
+});
+
+it("isPreview is undefined for unversioned service", async () => {
+  const { program } = await SimpleTester.compile(`
+    @service
+    namespace TestService;
+    op test(): void;
+  `);
+
+  const context = await createSdkContextForTester(program);
+  const sdkPackage = context.sdkPackage;
+  strictEqual(sdkPackage.metadata.apiVersion, undefined);
+  strictEqual(sdkPackage.metadata.isPreview, undefined);
+});
+
+it("isPreview is true for service with preview suffix version", async () => {
+  const { program } = await SimpleTester.compile(`
+    @service
+    @versioned(Versions)
+    namespace TestService;
+    enum Versions {
+      v2024_10_01_preview: "2024-10-01-preview",
+    }
+    op test(): void;
+  `);
+
+  const context = await createSdkContextForTester(program);
+  const sdkPackage = context.sdkPackage;
+  strictEqual(sdkPackage.metadata.isPreview, true);
+});
+
+it("isPreview is true for service with mixed stable and preview versions", async () => {
+  const { program } = await SimpleTester.compile(`
+    @service
+    @versioned(Versions)
+    namespace TestService;
+    enum Versions {
+      v2024_10_01: "2024-10-01",
+      v2024_11_01_preview: "2024-11-01-preview",
+    }
+    op test(): void;
+  `);
+
+  const context = await createSdkContextForTester(program);
+  const sdkPackage = context.sdkPackage;
+  strictEqual(sdkPackage.metadata.isPreview, true);
+});
+
+it("isPreview is true for service with @previewVersion decorator", async () => {
+  const { program } = await AzureCoreTester.compile(`
+    @service
+    @versioned(Versions)
+    namespace TestService;
+    enum Versions {
+      v2022_10_01: "2022-10-01",
+      #suppress "@azure-tools/typespec-azure-core/preview-version-last-member" "for test"
+      @previewVersion
+      v2022_11_01: "2022-11-01",
+      v2024_10_01: "2024-10-01",
+    }
+    op test(): void;
+  `);
+
+  const context = await createSdkContextForTester(program);
+  const sdkPackage = context.sdkPackage;
+  strictEqual(sdkPackage.metadata.isPreview, true);
+});