[http-client-csharp] fix: use inputmodel name as default name in seri…

…alization provider (#4823)

This PR fixes an issue where the name of the serialization provider for
a model was being built incorrectly when the model is renamed and the
renamed model is also further customized. It addresses this issue by
ensuring the default name of the serialization provider is the name of
the input model it is constructed from.

fixes: #4793

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

@@ -88,7 +88,7 @@ public MrwSerializationTypeDefinition(InputModelType inputModel, ModelProvider m
 
         protected override string BuildRelativeFilePath() => Path.Combine("src", "Generated", "Models", $"{Name}.Serialization.cs");
 
-        protected override string BuildName() => _model.Name;
+        protected override string BuildName() => _inputModel.Name.ToCleanName();
 
         protected override IReadOnlyList<AttributeStatement> BuildAttributes()
         {

packages/http-client-csharp/generator/Microsoft.Generator.CSharp.ClientModel/test/Providers/MrwSerializationTypeDefinitions/ModelCustomizationTests.cs

@@ -228,5 +228,27 @@ public async Task CanCustomizeEnumToFieldFrameworkType()
             var file = writer.Write();
             Assert.AreEqual(Helpers.GetExpectedFromFile(), file.Content);
         }
+
+        [Test]
+        public async Task CanCustomizeModelName()
+        {
+            await MockHelpers.LoadMockPluginAsync(compilation: async () => await Helpers.GetCompilationFromDirectoryAsync());
+            var inputModel = InputFactory.Model("mockInputModel", properties: [], usage: InputModelTypeUsage.Json);
+
+            var plugin = await MockHelpers.LoadMockPluginAsync(
+                inputModels: () => [inputModel],
+                compilation: async () => await Helpers.GetCompilationFromDirectoryAsync());
+
+            var modelProvider = plugin.Object.OutputLibrary.TypeProviders.Single(t => t is ModelProvider);
+            var serializationProvider = modelProvider.SerializationProviders.Single(t => t is MrwSerializationTypeDefinition);
+            Assert.IsNotNull(serializationProvider);
+
+            // both providers should have the custom name
+            Assert.AreEqual("CustomModel", modelProvider.Name);
+            Assert.AreEqual("CustomModel", serializationProvider.Name);
+
+            Assert.AreEqual("CustomModel", modelProvider.CustomCodeView?.Name);
+            Assert.AreEqual("CustomModel", serializationProvider.CustomCodeView?.Name);
+        }
     }
 }

packages/http-client-csharp/generator/Microsoft.Generator.CSharp.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/ModelCustomizationTests/CanCustomizeModelName/CustomModel.cs

@@ -0,0 +1,9 @@
+#nullable disable
+
+using Microsoft.Generator.CSharp.Customization;
+
+namespace Sample.Models
+{
+    [CodeGenModel("MockInputModel")]
+    internal partial class CustomModel { }
+}