Fix #1048 Allow void in final result for Azure-AsyncOperation header

.chronus/changes/async-header-result-2024-6-15-23-4-6.md

@@ -0,0 +1,8 @@
+---
+# Change versionKind to one of: internal, fix, dependencies, feature, deprecation, breaking
+changeKind: fix
+packages:
+  - "@azure-tools/typespec-azure-resource-manager"
+---
+
+Fix #1048 Allow void in final result for Azure-AsyncOperation header

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

@@ -120,6 +120,7 @@ describe("typespec-autorest: Long-running Operations", () => {
         delete is ArmResourceDeleteWithoutOkAsync<Widget>;
         restart is ArmResourceActionAsync<Widget, void, never>;
         munge is ArmResourceActionAsync<Widget, void, Widget>;
+        alter is ArmResourceActionAsync<Widget, void, void, LroHeaders=ArmAsyncOperationHeader<FinalResult = void>>;
         listByResourceGroup is ArmResourceListByParent<Widget>;
         listBySubscription is ArmListBySubscription<Widget>;
       }
@@ -162,6 +163,11 @@ describe("typespec-autorest: Long-running Operations", () => {
       "final-state-via": "location",
       "final-state-schema": "#/definitions/Widget",
     });
+    const alterPath = `${itemPath}/alter`;
+    deepStrictEqual(openapi.paths[alterPath].post["x-ms-long-running-operation"], true);
+    deepStrictEqual(openapi.paths[alterPath].post["x-ms-long-running-operation-options"], {
+      "final-state-via": "azure-async-operation",
+    });
   });
   it("Uses final-state-via: location when location is provided for ARM PUT", async () => {
     const openapi = await openApiFor(

packages/typespec-azure-resource-manager/lib/responses.tsp

@@ -138,7 +138,7 @@ model ArmOperationStatus<
 model ArmAsyncOperationHeader<
   StatusMonitor extends {} = ArmOperationStatus,
   UrlValue extends string = string,
-  FinalResult extends {} = never
+  FinalResult extends {} | void = never
 > {
   /** A link to the status monitor */
   @header("Azure-AsyncOperation")

packages/typespec-azure-resource-manager/test/lro-metadata.test.ts

@@ -310,6 +310,71 @@ describe("typespec-azure-resource-manager: ARM LRO Tests", () => {
     deepStrictEqual(metadata.finalResultPath, undefined);
     deepStrictEqual(metadata.finalStateVia, "location");
   });
+  it("Returns correct metadata for Async action with void return type", async () => {
+    const [metadata, _diag, _runner] = await getLroMetadataFor(
+      `
+  @armProviderNamespace
+      @useDependency(Azure.ResourceManager.Versions.v1_0_Preview_1)
+      namespace Microsoft.Test;
+
+      interface Operations extends Azure.ResourceManager.Operations {}
+
+      @doc("The state of the resource")
+      enum ResourceState {
+       Succeeded,
+       Canceled,
+       Failed
+     }
+
+      @doc("The widget properties")
+      model WidgetProperties {
+        @doc("I am a simple Resource Identifier")
+        simpleArmId: ResourceIdentifier;
+
+        @doc("The provisioning State")
+        provisioningState: ResourceState;
+      }
+
+      @doc("The result of the post request")
+      model ResultModel {
+        @doc("The result message")
+        message: string;
+      }
+
+      @doc("The request of the post request")
+      model RequestModel {
+        @doc("The request message")
+        message: string;
+      }
+
+      @doc("Foo resource")
+      model Widget is TrackedResource<WidgetProperties> {
+        @doc("Widget name")
+        @key("widgetName")
+        @segment("widgets")
+        @path
+        name: string;
+      }
+
+      @armResourceOperations(Widget)
+      interface Widgets {
+        get is ArmResourceRead<Widget>;
+        createOrUpdate is ArmResourceCreateOrReplaceAsync<Widget>;
+        update is ArmResourcePatchSync<Widget, WidgetProperties>;
+        delete is ArmResourceDeleteSync<Widget>;
+        doStuff is ArmResourceActionAsync<Widget, RequestModel, void, LroHeaders=ArmAsyncOperationHeader<FinalResult = void>>;
+        listByResourceGroup is ArmResourceListByParent<Widget>;
+        listBySubscription is ArmListBySubscription<Widget>;
+      }
+      `,
+      "doStuff"
+    );
+    ok(metadata);
+    deepStrictEqual(metadata.finalResult, "void");
+    deepStrictEqual(metadata.finalEnvelopeResult, "void");
+    deepStrictEqual(metadata.finalResultPath, undefined);
+    deepStrictEqual(metadata.finalStateVia, "azure-async-operation");
+  });
 
   it("Returns correct metadata for Async CreateOrUpdate with union type ProvisioningState", async () => {
     const [metadata, _diag, _runner] = await getLroMetadataFor(