Fix Go example generator emitting invalid Go for RFC7231 datetime values

.chronus/changes/copilot-fix-invalid-go-rfc7231-datetime-2026-6-21-5-57-23.md

@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@azure-tools/typespec-go"
+---
+
+Fix the example generator emitting incorrect code for `rfc7231` datatime.

packages/typespec-go/docs/development.md

@@ -210,4 +210,4 @@ Before you do, make sure to:
 
 1. Format your code (`pnpm format` from the repo root, or check with `pnpm format:check`).
 2. Rebuild and regenerate everything so the committed fixtures reflect your change.
-3. Add a changelog entry with [Chronus](https://github.com/microsoft/chronus) by running `pnpm exec chronus add` from the repo root and following the prompts. This creates a change file under `.chronus/changes/` that you should commit with your PR.
+3. Add a changelog entry with [Chronus](https://github.com/microsoft/chronus) by running `pnpm change add` from the repo root and following the prompts. This creates a change file under `.chronus/changes/` that you should commit with your PR.

packages/typespec-go/src/codegen/core/example.ts

@@ -450,6 +450,7 @@ function getTimeValue(type: go.Time, value: any, imports?: ImportManager): strin
     PlainTime: helpers.plainTimeFormat,
     RFC1123: helpers.RFC1123Format,
     RFC3339: helpers.RFC3339Format,
+    RFC7231: helpers.RFC1123Format,
   };
 
   if (type.format in formatMap) {

packages/typespec-go/test/unittest/scenario-suites/rfc7231-datetime-sample.test.ts

@@ -0,0 +1,5 @@
+// Generated by `pnpm gen:scenario-suites`. Do not edit by hand.
+import { resolvePath } from "@typespec/compiler";
+import { describeScenarioFile } from "../scenario-runner.js";
+
+describeScenarioFile(resolvePath(import.meta.dirname, "../scenarios/rfc7231-datetime-sample.md"));

packages/typespec-go/test/unittest/scenarios/rfc7231-datetime-sample.md

@@ -0,0 +1,136 @@
+# A `utcDateTime` property encoded as `rfc7231` generates a sample that parses the value with `time.RFC1123`
+
+```yaml
+generate-samples: true
+```
+
+## TypeSpec
+
+```tsp
+@armProviderNamespace
+namespace Microsoft.Test;
+
+union ProvisioningState {
+  string,
+  Succeeded: "Succeeded",
+  Failed: "Failed",
+  Canceled: "Canceled",
+}
+
+model WidgetProperties {
+  description?: string;
+
+  @encode("rfc7231")
+  lastExecuted?: utcDateTime;
+
+  @visibility(Lifecycle.Read)
+  provisioningState?: ProvisioningState;
+}
+
+model Widget is TrackedResource<WidgetProperties> {
+  @path
+  @key("widgetName")
+  @segment("widgets")
+  name: string;
+}
+
+@armResourceOperations
+interface Widgets {
+  put is ArmResourceCreateOrReplaceSync<Widget>;
+}
+```
+
+## The example inputs
+
+```json examples/Widgets_put.json
+{
+  "operationId": "Widgets_put",
+  "title": "Widgets_put",
+  "parameters": {
+    "api-version": "2025-01-01",
+    "subscriptionId": "00000000-0000-0000-0000-000000000000",
+    "resourceGroupName": "myResourceGroup",
+    "widgetName": "myWidget",
+    "resource": {
+      "location": "eastus",
+      "properties": {
+        "description": "my widget",
+        "lastExecuted": "05 May 2021 12:00:23 GMT"
+      }
+    }
+  },
+  "responses": {
+    "200": {
+      "body": {
+        "id": "/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/myResourceGroup/providers/Microsoft.Test/widgets/myWidget",
+        "name": "myWidget",
+        "type": "Microsoft.Test/widgets",
+        "location": "eastus",
+        "properties": {
+          "description": "my widget",
+          "lastExecuted": "05 May 2021 12:00:23 GMT",
+          "provisioningState": "Succeeded"
+        }
+      }
+    }
+  }
+}
+```
+
+## The generated sample parses the `rfc7231` datetime with `time.RFC1123`
+
+```go widgets_client_example_test
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License. See License.txt in the project root for license information.
+// Code generated by Microsoft (R) Go Code Generator. DO NOT EDIT.
+
+package testmodule_test
+
+import (
+	"context"
+	"github.com/Azure/azure-sdk-for-go/sdk/azcore/to"
+	"github.com/Azure/azure-sdk-for-go/sdk/azidentity"
+	"log"
+	"testmodule"
+	"time"
+)
+
+// Generated from example definition: Widgets_put.json
+func ExampleWidgetsClient_Put() {
+	cred, err := azidentity.NewDefaultAzureCredential(nil)
+	if err != nil {
+		log.Fatalf("failed to obtain a credential: %v", err)
+	}
+	ctx := context.Background()
+	clientFactory, err := testmodule.NewClientFactory("00000000-0000-0000-0000-000000000000", cred, nil)
+	if err != nil {
+		log.Fatalf("failed to create client: %v", err)
+	}
+	res, err := clientFactory.NewWidgetsClient().Put(ctx, "2025-01-01", "myResourceGroup", "myWidget", testmodule.Widget{
+		Location: to.Ptr("eastus"),
+		Properties: &testmodule.WidgetProperties{
+			Description:  to.Ptr("my widget"),
+			LastExecuted: to.Ptr(func() time.Time { t, _ := time.Parse(time.RFC1123, "05 May 2021 12:00:23 GMT"); return t }()),
+		},
+	}, nil)
+	if err != nil {
+		log.Fatalf("failed to finish the request: %v", err)
+	}
+	// You could use response here. We use blank identifier for just demo purposes.
+	_ = res
+	// If the HTTP response code is 200 as defined in example definition, your response structure would look as follows. Please pay attention that all the values in the output are fake values for just demo purposes.
+	// res = testmodule.WidgetsClientPutResponse{
+	// 	Widget: testmodule.Widget{
+	// 		ID: to.Ptr("/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/myResourceGroup/providers/Microsoft.Test/widgets/myWidget"),
+	// 		Name: to.Ptr("myWidget"),
+	// 		Type: to.Ptr("Microsoft.Test/widgets"),
+	// 		Location: to.Ptr("eastus"),
+	// 		Properties: &testmodule.WidgetProperties{
+	// 			Description: to.Ptr("my widget"),
+	// 			LastExecuted: to.Ptr(func() time.Time { t, _ := time.Parse(time.RFC1123, "05 May 2021 12:00:23 GMT"); return t}()),
+	// 			ProvisioningState: to.Ptr(testmodule.ProvisioningStateSucceeded),
+	// 		},
+	// 	},
+	// }
+}
+```