Keep REST request names stable across wrapper contracts

packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/src/Providers/ClientProvider.cs

@@ -211,13 +211,13 @@ private void CleanOperationNames(InputClient inputClient)
         {
             foreach (var serviceMethod in inputClient.Methods)
             {
-                var updatedOperationName = GetCleanOperationName(serviceMethod);
+                var updatedOperationName = GetOperationName(serviceMethod);
                 serviceMethod.Update(name: updatedOperationName);
                 serviceMethod.Operation.Update(name: updatedOperationName);
             }
         }
 
-        private string GetCleanOperationName(InputServiceMethod serviceMethod)
+        private string GetOperationName(InputServiceMethod serviceMethod, bool normalizeUrlSuffix = true)
         {
             if (serviceMethod.IsExactName)
             {
@@ -237,6 +237,11 @@ private string GetCleanOperationName(InputServiceMethod serviceMethod)
                 operationName = $"Get{operationName.Substring(4)}";
             }
 
+            if (!normalizeUrlSuffix)
+            {
+                return operationName;
+            }
+
             var normalizedName = operationName.NormalizeCSharpUrlSuffix();
             if (normalizedName == operationName)
             {
@@ -254,6 +259,14 @@ private string GetCleanOperationName(InputServiceMethod serviceMethod)
             return normalizedName;
         }
 
+        internal string GetRestOperationName(InputServiceMethod serviceMethod)
+        {
+            // Request builders use the stable input operation identity rather than the mutable public method name.
+            // Preserve the original Url suffix so a projection honoring a previous GA name and a newer projection
+            // normalized to Uri continue to reference the same request builder.
+            return GetOperationName(serviceMethod, normalizeUrlSuffix: false).ToIdentifierName();
+        }
+
         private string? _namespace;
         // This `BuildNamespace` method has been called twice - one when building the `Type`, the other is trying to find the CustomCodeView, both of them are required.
         // therefore here to avoid this being called twice because this method now reports a diagnostic, we cache the result.

packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/src/Providers/RestClientProvider.cs

@@ -230,10 +230,10 @@ private ScmMethodProvider BuildCreateRequestMethod(InputServiceMethod serviceMet
                 parameters = [ScmKnownParameters.NextPage, .. parameters];
             }
 
-            var operation = serviceMethod.Operation;
+            var operationName = ClientProvider.GetRestOperationName(serviceMethod);
             var methodName = isNextLinkRequest
-                ? $"CreateNext{operation.Name.ToIdentifierName()}Request"
-                : $"Create{operation.Name.ToIdentifierName()}Request";
+                ? $"CreateNext{operationName}Request"
+                : $"Create{operationName}Request";
             var signature = new MethodSignature(
                 methodName,
                 null,

packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/ClientProviders/ClientProviderTests.cs

@@ -4708,11 +4708,12 @@ public void TestIsExactNameServiceMethodPreservesOperationNameVerbatim()
             var inputOperation = InputFactory.Operation("snake_case_op", isExactName: true);
             var inputServiceMethod = InputFactory.BasicServiceMethod("snake_case_op", inputOperation, isExactName: true);
             var client = InputFactory.Client("TestClient", methods: [inputServiceMethod]);
-            _ = new ClientProvider(client);
+            var clientProvider = new ClientProvider(client);
 
             // After CleanOperationNames runs in the ClientProvider constructor, names should be unchanged.
             Assert.AreEqual("snake_case_op", inputServiceMethod.Name);
             Assert.AreEqual("snake_case_op", inputServiceMethod.Operation.Name);
+            Assert.AreEqual("CreateSnakeCaseOpRequest", clientProvider.RestClient.GetCreateRequestMethod(inputOperation).Signature.Name);
         }
 
         [TestCase("GetUrl", false, "GetUri")]
@@ -4791,6 +4792,37 @@ public async Task TestOperationNameFallsBackToClientLastContractWhenBackCompatPr
             Assert.IsTrue(methods.Any(m => m.Signature.Name == "GetUrl"));
         }
 
+        [Test]
+        public async Task TestEarlierWrapperRequestExistsAfterLaterBackCompatProvider()
+        {
+            var inputOperation = InputFactory.Operation("GetUrl");
+            var inputServiceMethod = InputFactory.BasicServiceMethod("GetUrl", inputOperation);
+            var client = InputFactory.Client("TestClient", methods: [inputServiceMethod]);
+            var generator = await MockHelpers.LoadMockGeneratorAsync(
+                clients: () => [client],
+                lastContractCompilation: async () => await Helpers.GetCompilationFromDirectoryAsync());
+            var clientProvider = generator.Object.OutputLibrary.TypeProviders.OfType<ClientProvider>().Single();
+            var shippedWrapper = new BackCompatTypeProvider("MockableTestResource", "Sample");
+
+            var shippedWrapperMethods = clientProvider.GetMethodCollectionByOperation(inputOperation, shippedWrapper);
+            var publicMethodName = shippedWrapperMethods.Single(m =>
+                m.Kind == ScmMethodKind.Convenience &&
+                !m.Signature.Modifiers.HasFlag(MethodSignatureModifiers.Async)).Signature.Name;
+            var capturedRequestMethodName = clientProvider.RestClient.GetCreateRequestMethod(inputOperation).Signature.Name;
+
+            Assert.AreEqual("GetUrl", publicMethodName);
+            Assert.AreEqual("CreateGetUrlRequest", capturedRequestMethodName);
+
+            var newWrapper = new BackCompatTypeProvider("MissingWrapper", "Sample");
+            _ = clientProvider.GetMethodCollectionByOperation(inputOperation, newWrapper);
+
+            var emittedRestClient = new TypeProviderWriter(clientProvider.RestClient).Write().Content;
+            StringAssert.Contains(
+                $"{capturedRequestMethodName}(",
+                emittedRestClient,
+                "The final REST client must emit the request method captured by an earlier wrapper projection.");
+        }
+
         [Test]
         public void TestIsExactNameServiceMethodSkipsListToGetRename()
         {

packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/ClientProviders/TestData/ClientProviderTests/TestEarlierWrapperRequestExistsAfterLaterBackCompatProvider/MockableTestResource.cs

@@ -0,0 +1,12 @@
+using System.ClientModel;
+using System.Threading.Tasks;
+
+namespace Sample
+{
+    public partial class MockableTestResource
+    {
+        public virtual ClientResult GetUrl() => default!;
+
+        public virtual Task<ClientResult> GetUrlAsync() => default!;
+    }
+}

packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/RestClientProviders/TestData/RestClientProviderTests/TestBuildCreateRequestMethodWithQueryInPath.cs

@@ -8,7 +8,7 @@ namespace Sample
 {
     public partial class TestClient
     {
-        internal global::System.ClientModel.Primitives.PipelineMessage CreateAbortCopyFromUriRequest(string copyid, global::System.ClientModel.Primitives.RequestOptions options)
+        internal global::System.ClientModel.Primitives.PipelineMessage CreateAbortCopyFromUrlRequest(string copyid, global::System.ClientModel.Primitives.RequestOptions options)
         {
             global::Sample.ClientUriBuilder uri = new global::Sample.ClientUriBuilder();
             uri.Reset(_endpoint);

packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/RestClientProviders/TestData/RestClientProviderTests/TestBuildCreateRequestMethodWithSlashQueryInPath.cs

@@ -8,7 +8,7 @@ namespace Sample
 {
     public partial class TestClient
     {
-        internal global::System.ClientModel.Primitives.PipelineMessage CreateAbortCopyFromUriRequest(string copyid, global::System.ClientModel.Primitives.RequestOptions options)
+        internal global::System.ClientModel.Primitives.PipelineMessage CreateAbortCopyFromUrlRequest(string copyid, global::System.ClientModel.Primitives.RequestOptions options)
         {
             global::Sample.ClientUriBuilder uri = new global::Sample.ClientUriBuilder();
             uri.Reset(_endpoint);