Specs/add common package ref test

.chronus/changes/add-common-package-ref-test-2026-5-5-14-51-0.md

@@ -0,0 +1,7 @@
+---
+changeKind: feature
+packages:
+  - "@azure-tools/azure-http-specs"
+---
+
+Add common package reference test for `@alternateType` with `ExternalType`. This test demonstrates using `@alternateType` to reference types from a pre-existing typespec-defined common package, where each language emitter specifies its own generated package coordinates. Includes a models-only `common-types` spector package defining an `Address` model.

packages/azure-http-specs/specs/azure/client-generator-core/alternate-type/common-package-ref/client.tsp

@@ -0,0 +1,54 @@
+import "@azure-tools/typespec-client-generator-core";
+import "./main.tsp";
+
+using Azure.ClientGenerator.Core;
+
+// Python: reference from the generated common-types package
+@@alternateType(_Specs_.Azure.ClientGenerator.Core.AlternateType.CommonPackageRef.Address,
+  {
+    identity: "common_types.models.Address",
+    package: "common-types",
+    minVersion: "1.0.0",
+  },
+  "python"
+);
+
+// Java: reference from the generated common-types package
+@@alternateType(_Specs_.Azure.ClientGenerator.Core.AlternateType.CommonPackageRef.Address,
+  {
+    identity: "com.azure.common.types.models.Address",
+    package: "com.azure.common-types",
+    minVersion: "1.0.0",
+  },
+  "java"
+);
+
+// C#: reference from the generated common-types package
+@@alternateType(_Specs_.Azure.ClientGenerator.Core.AlternateType.CommonPackageRef.Address,
+  {
+    identity: "CommonTypes.Models.Address",
+    package: "CommonTypes",
+    minVersion: "1.0.0",
+  },
+  "csharp"
+);
+
+// TypeScript: reference from the generated common-types package
+@@alternateType(_Specs_.Azure.ClientGenerator.Core.AlternateType.CommonPackageRef.Address,
+  {
+    identity: "Address",
+    package: "common-types",
+    minVersion: "1.0.0",
+  },
+  "typescript"
+);
+
+// Go: reference from the generated common-types package
+@@alternateType(_Specs_.Azure.ClientGenerator.Core.AlternateType.CommonPackageRef.Address,
+  {
+    identity: "commontypes.Address",
+    package: "github.com/Azure/azure-sdk-for-go/sdk/common-types",
+    minVersion: "1.0.0",
+  },
+  "go"
+);

packages/azure-http-specs/specs/azure/client-generator-core/alternate-type/common-package-ref/common-types/main.tsp

@@ -0,0 +1,22 @@
+import "@typespec/http";
+import "@typespec/spector";
+
+using Http;
+using Spector;
+
+/**
+ * A models-only TypeSpec package representing pre-generated common/shared types.
+ *
+ * Language emitters should generate this package independently, then services
+ * that use `@alternateType` with `ExternalType` can reference the generated
+ * package instead of re-generating these types inline.
+ */
+@scenarioService("/azure/client-generator-core/alternate-type/common-package-ref/common-types")
+@service
+namespace _Specs_.Azure.ClientGenerator.Core.AlternateType.CommonPackageRef.CommonTypes;
+
+/** A postal address. */
+model Address {
+  city: string;
+  state: string;
+}

packages/azure-http-specs/specs/azure/client-generator-core/alternate-type/common-package-ref/common-types/mockapi.ts

@@ -0,0 +1,4 @@
+import { ScenarioMockApi } from "@typespec/spec-api";
+
+// Models-only package — no operations, no scenarios.
+export const Scenarios: Record<string, ScenarioMockApi> = {};

packages/azure-http-specs/specs/azure/client-generator-core/alternate-type/common-package-ref/main.tsp

@@ -0,0 +1,98 @@
+import "@typespec/http";
+import "@typespec/spector";
+import "@azure-tools/typespec-client-generator-core";
+
+using Http;
+using Azure.ClientGenerator.Core;
+using Spector;
+
+@doc("""
+  Test using @alternateType with ExternalType to reference a pre-existing
+  typespec-defined common package. Instead of generating types inline,
+  language emitters should reference the types from the common package.
+  """)
+@scenarioService("/azure/client-generator-core/alternate-type/common-package-ref")
+@service
+namespace _Specs_.Azure.ClientGenerator.Core.AlternateType.CommonPackageRef;
+
+/** Address model that mirrors the common package's Address type on the wire. */
+model Address {
+  city: string;
+  state: string;
+}
+
+/** Model that has a property referencing the common package type. */
+model ModelWithAddressProperty {
+  address: Address;
+  name: string;
+}
+
+@scenario
+@scenarioDoc("""
+  Input: None
+  Output: Address object.
+  Example response:
+  ```json
+  {
+    "city": "Seattle",
+    "state": "WA"
+  }
+  ```
+  """)
+@route("/model")
+@get
+op getModel(): Address;
+
+@scenario
+@scenarioDoc("""
+  Input: Address object in request body.
+  Example input:
+  ```json
+  {
+    "city": "Seattle",
+    "state": "WA"
+  }
+  ```
+  Output: None (204/empty response)
+  """)
+@route("/model")
+@put
+op putModel(@body body: Address): void;
+
+@scenario
+@scenarioDoc("""
+  Input: None
+  Output: ModelWithAddressProperty object.
+  Example response:
+  ```json
+  {
+    "address": {
+      "city": "Seattle",
+      "state": "WA"
+    },
+    "name": "test"
+  }
+  ```
+  """)
+@route("/property")
+@get
+op getProperty(): ModelWithAddressProperty;
+
+@scenario
+@scenarioDoc("""
+  Input: ModelWithAddressProperty object in request body.
+  Example input:
+  ```json
+  {
+    "address": {
+      "city": "Seattle",
+      "state": "WA"
+    },
+    "name": "test"
+  }
+  ```
+  Output: None (204/empty response)
+  """)
+@route("/property")
+@put
+op putProperty(@body body: ModelWithAddressProperty): void;

packages/azure-http-specs/specs/azure/client-generator-core/alternate-type/common-package-ref/mockapi.ts

@@ -0,0 +1,66 @@
+import {
+  json,
+  MockApiDefinition,
+  MockBody,
+  passOnSuccess,
+  ScenarioMockApi,
+} from "@typespec/spec-api";
+
+export const Scenarios: Record<string, ScenarioMockApi> = {};
+
+function createMockApiDefinitions(
+  route: string,
+  body: MockBody,
+): [MockApiDefinition, MockApiDefinition] {
+  return [
+    {
+      uri: `/azure/client-generator-core/alternate-type/common-package-ref/${route}`,
+      method: "get",
+      response: {
+        status: 200,
+        body: body,
+      },
+      kind: "MockApiDefinition",
+    },
+    {
+      uri: `/azure/client-generator-core/alternate-type/common-package-ref/${route}`,
+      method: "put",
+      request: {
+        body,
+      },
+      response: { status: 204 },
+      kind: "MockApiDefinition",
+    },
+  ];
+}
+
+const address = {
+  city: "Seattle",
+  state: "WA",
+};
+
+const modelScenarioTypes = createMockApiDefinitions("model", json(address));
+
+Scenarios.Azure_ClientGenerator_Core_AlternateType_CommonPackageRef_getModel = passOnSuccess(
+  modelScenarioTypes[0],
+);
+Scenarios.Azure_ClientGenerator_Core_AlternateType_CommonPackageRef_putModel = passOnSuccess(
+  modelScenarioTypes[1],
+);
+
+const modelWithAddressProperty = {
+  address,
+  name: "test",
+};
+
+const modelPropertyScenarioTypes = createMockApiDefinitions(
+  "property",
+  json(modelWithAddressProperty),
+);
+
+Scenarios.Azure_ClientGenerator_Core_AlternateType_CommonPackageRef_getProperty = passOnSuccess(
+  modelPropertyScenarioTypes[0],
+);
+Scenarios.Azure_ClientGenerator_Core_AlternateType_CommonPackageRef_putProperty = passOnSuccess(
+  modelPropertyScenarioTypes[1],
+);