Fix explicit operator param name and remove no-op assignment (#8858)

Contributes to Azure/azure-sdk-for-net#53553

Also, removes disposal of the raw response - this is a no-op for
buffered streams, but for unbuffered it is the library user's
responsibility.

Author: JoshLove-msft

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

@@ -39,6 +39,7 @@ protected ClientResponseApi(Type type, ValueExpression original) : base(type, or
 
         public abstract CSharpType ClientCollectionResponseOfTType { get; }
         public abstract CSharpType ClientCollectionAsyncResponseOfTType { get; }
+        public abstract string ResponseParameterName { get; }
 
         public abstract TypeProvider CreateClientCollectionResultDefinition(
             ClientProvider client,

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

@@ -23,6 +23,8 @@ public interface IClientResponseApi : IExpressionApi<ClientResponseApi>
 
         CSharpType ClientCollectionAsyncResponseOfTType { get; }
 
+        string ResponseParameterName { get; }
+
         TypeProvider CreateClientCollectionResultDefinition(
             ClientProvider client,
             InputPagingServiceMethod serviceMethod,

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

@@ -28,6 +28,7 @@ public ClientResultProvider(ValueExpression clientResult) : base(typeof(ClientRe
         public override CSharpType ClientCollectionAsyncResponseType => typeof(AsyncCollectionResult);
         public override CSharpType ClientCollectionResponseOfTType => typeof(CollectionResult<>);
         public override CSharpType ClientCollectionAsyncResponseOfTType => typeof(AsyncCollectionResult<>);
+        public override string ResponseParameterName => "result";
 
         public override TypeProvider CreateClientCollectionResultDefinition(
             ClientProvider client,

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

@@ -216,10 +216,27 @@ protected override MethodProvider[] BuildMethods()
 
         private MethodProvider BuildExplicitFromClientResult()
         {
-            var result = new ParameterProvider("result", $"The {ScmCodeModelGenerator.Instance.TypeFactory.ClientResponseApi.ClientResponseType:C} to deserialize the {Type:C} from.", ScmCodeModelGenerator.Instance.TypeFactory.ClientResponseApi.ClientResponseType);
-            var modifiers = MethodSignatureModifiers.Public | MethodSignatureModifiers.Static | MethodSignatureModifiers.Explicit | MethodSignatureModifiers.Operator;
+            var result = new ParameterProvider(
+                ScmCodeModelGenerator.Instance.TypeFactory.ClientResponseApi.ResponseParameterName,
+                $"The {ScmCodeModelGenerator.Instance.TypeFactory.ClientResponseApi.ClientResponseType:C} to deserialize the {Type:C} from.",
+                ScmCodeModelGenerator.Instance.TypeFactory.ClientResponseApi.ClientResponseType);
+            var modifiers = MethodSignatureModifiers.Public | MethodSignatureModifiers.Static |
+                            MethodSignatureModifiers.Explicit | MethodSignatureModifiers.Operator;
             // using PipelineResponse response = result.GetRawResponse();
-            var responseDeclaration = UsingDeclare("response", ScmCodeModelGenerator.Instance.TypeFactory.HttpResponseApi.HttpResponseType, result.ToApi<ClientResponseApi>().GetRawResponse(), out var response);
+            var response = result.ToApi<ClientResponseApi>();
+            MethodBodyStatement responseDeclaration;
+
+            // if the GetRawResponse is a no-op we don't need to declare a new variable
+            if (response.Original == response.GetRawResponse().Original)
+            {
+                responseDeclaration = MethodBodyStatement.Empty;
+            }
+            else
+            {
+                responseDeclaration = Declare("response", ScmCodeModelGenerator.Instance.TypeFactory.HttpResponseApi.HttpResponseType, result.ToApi<ClientResponseApi>().GetRawResponse(), out var responseVar);
+                response = responseVar.ToApi<ClientResponseApi>();
+            }
+
             MethodBodyStatement[] methodBody;
 
             if (_model is ScmModelProvider { HasDynamicModelSupport: true })

packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/Abstractions/ClientResponseApiTests.cs

@@ -22,7 +22,7 @@ internal class ClientResponseApiTests
         [Test]
         public void ValidateReturnTypeIsOverridden()
         {
-            ClientProvider clientProvider = CreateMockClientProvider();
+            (ClientProvider clientProvider, _) = CreateMockClientProvider();
 
             // take the sync version of the method from the client provider
             var method = clientProvider.Methods.FirstOrDefault(x => !x.Signature.Name.EndsWith("Async"));
@@ -34,7 +34,7 @@ public void ValidateReturnTypeIsOverridden()
         [Test]
         public void ValidateBodyOfClientOperationIsOverridden()
         {
-            var clientProvider = CreateMockClientProvider();
+            (ClientProvider clientProvider, _) = CreateMockClientProvider();
 
             // take the sync version of the method from the client provider
             var method = clientProvider.Methods.FirstOrDefault(x => x.Signature.Parameters.Any(p => p.Type.Equals(typeof(RequestOptions))) && !x.Signature.Name.EndsWith("Async"));
@@ -43,14 +43,42 @@ public void ValidateBodyOfClientOperationIsOverridden()
             Assert.AreEqual(Helpers.GetExpectedFromFile(), method.BodyStatements!.ToDisplayString());
         }
 
-        private static ClientProvider CreateMockClientProvider()
+        [Test]
+        public void ValidateExplicitOperator()
+        {
+            (_, ModelProvider modelProvider) = CreateMockClientProvider();
+
+            var explicitOperator = modelProvider.SerializationProviders.First().Methods.FirstOrDefault(m => m.Signature.Modifiers.HasFlag(MethodSignatureModifiers.Explicit));
+            Assert.NotNull(explicitOperator);
+            var parameter = explicitOperator!.Signature.Parameters.FirstOrDefault();
+            Assert.NotNull(parameter);
+            Assert.AreEqual("stringResponse", parameter!.Name);
+            Assert.AreEqual(Helpers.GetExpectedFromFile(), explicitOperator!.BodyStatements!.ToDisplayString());
+        }
+
+        private static (ClientProvider, ModelProvider) CreateMockClientProvider()
         {
-            var inputServiceMethod = InputFactory.BasicServiceMethod("foo", InputFactory.Operation("foo"));
+            var responseModel = InputFactory.Model("Bar");
+            var operationResponse = InputFactory.OperationResponse(bodytype: responseModel);
+            var serviceResponse = InputFactory.ServiceMethodResponse(responseModel, null);
+            var inputServiceMethod = InputFactory.BasicServiceMethod("foo", InputFactory.Operation("foo", responses: [operationResponse]), response: serviceResponse);
             var client = InputFactory.Client("TestClient", methods: [inputServiceMethod]);
-            MockHelpers.LoadMockGenerator(clientResponseApi: TestClientResponseApi.Instance);
-            var clientProvider = ScmCodeModelGenerator.Instance.TypeFactory.CreateClient(client);
+
+            var generator = MockHelpers.LoadMockGenerator(
+                clientResponseApi: TestClientResponseApi.Instance,
+                inputModels: () => [responseModel],
+                clients: () => [client]);
+            var modelProvider = generator.Object.OutputLibrary.TypeProviders
+                .OfType<ModelProvider>()
+                .FirstOrDefault(m => m.Name == "Bar");
+            var clientProvider = generator.Object.OutputLibrary.TypeProviders
+                .OfType<ClientProvider>()
+                .FirstOrDefault(c => c.Name == "TestClient");
+
             Assert.IsNotNull(clientProvider);
-            return clientProvider!;
+            Assert.IsNotNull(modelProvider);
+
+            return (clientProvider!, modelProvider!);
         }
 
         private record TestClientResponseApi : ClientResponseApi
@@ -66,7 +94,7 @@ public TestClientResponseApi(ValueExpression origin) : base(typeof(string), orig
             }
 
             public override HttpResponseApi GetRawResponse()
-                => Original.Invoke("GetFakeRawResponse").ToApi<HttpResponseApi>();
+                => Original.ToApi<HttpResponseApi>();
 
             public override ValueExpression FromValue(ValueExpression valueExpression, HttpResponseApi response)
                 => Original.Invoke("GetFakeFromValue");
@@ -92,6 +120,7 @@ public override ClientResponseApi FromExpression(ValueExpression original)
             public override CSharpType ClientCollectionAsyncResponseType => typeof(AsyncCollectionResult);
             public override CSharpType ClientCollectionResponseOfTType => typeof(CollectionResult<>);
             public override CSharpType ClientCollectionAsyncResponseOfTType => typeof(AsyncCollectionResult<>);
+            public override string ResponseParameterName => "stringResponse";
 
             public override TypeProvider CreateClientCollectionResultDefinition(
                 ClientProvider client,

packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/Abstractions/TestData/ClientResponseApiTests/ValidateExplicitOperator.cs

@@ -0,0 +1,2 @@
+using global::System.Text.Json.JsonDocument document = global::System.Text.Json.JsonDocument.Parse(stringResponse.Content);
+return global::Sample.Models.Bar.DeserializeBar(document.RootElement, global::Sample.ModelSerializationExtensions.WireOptions);

packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/DynamicModelSerializationTests/ExplicitClientResultOperator(False).cs

@@ -13,7 +13,7 @@ public partial class Cat
     {
         public static explicit operator Cat(global::System.ClientModel.ClientResult result)
         {
-            using global::System.ClientModel.Primitives.PipelineResponse response = result.GetRawResponse();
+            global::System.ClientModel.Primitives.PipelineResponse response = result.GetRawResponse();
             using global::System.Text.Json.JsonDocument document = global::System.Text.Json.JsonDocument.Parse(response.Content);
             return global::Sample.Models.Cat.DeserializeCat(document.RootElement, global::Sample.ModelSerializationExtensions.WireOptions);
         }

packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/DynamicModelSerializationTests/ExplicitClientResultOperator(True).cs

@@ -14,7 +14,7 @@ public partial class Cat
     {
         public static explicit operator Cat(global::System.ClientModel.ClientResult result)
         {
-            using global::System.ClientModel.Primitives.PipelineResponse response = result.GetRawResponse();
+            global::System.ClientModel.Primitives.PipelineResponse response = result.GetRawResponse();
             global::System.BinaryData data = response.Content;
             using global::System.Text.Json.JsonDocument document = global::System.Text.Json.JsonDocument.Parse(data);
             return global::Sample.Models.Cat.DeserializeCat(document.RootElement, data, global::Sample.ModelSerializationExtensions.WireOptions);

packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/Friend.Serialization.cs

@@ -154,7 +154,7 @@ public static implicit operator BinaryContent(Friend friend)
         /// <param name="result"> The <see cref="ClientResult"/> to deserialize the <see cref="Friend"/> from. </param>
         public static explicit operator Friend(ClientResult result)
         {
-            using PipelineResponse response = result.GetRawResponse();
+            PipelineResponse response = result.GetRawResponse();
             using JsonDocument document = JsonDocument.Parse(response.Content);
             return DeserializeFriend(document.RootElement, ModelSerializationExtensions.WireOptions);
         }

packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/ListWithContinuationTokenHeaderResponseResponse.Serialization.cs

@@ -153,7 +153,7 @@ protected virtual ListWithContinuationTokenHeaderResponseResponse PersistableMod
         /// <param name="result"> The <see cref="ClientResult"/> to deserialize the <see cref="ListWithContinuationTokenHeaderResponseResponse"/> from. </param>
         public static explicit operator ListWithContinuationTokenHeaderResponseResponse(ClientResult result)
         {
-            using PipelineResponse response = result.GetRawResponse();
+            PipelineResponse response = result.GetRawResponse();
             using JsonDocument document = JsonDocument.Parse(response.Content);
             return DeserializeListWithContinuationTokenHeaderResponseResponse(document.RootElement, ModelSerializationExtensions.WireOptions);
         }