Add tests for supporting adding custom model props (#4474)

Add tests for #4263, which
is already supported.

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

@@ -6,7 +6,6 @@
 using System.Linq;
 using Microsoft.Generator.CSharp.Expressions;
 using Microsoft.Generator.CSharp.Primitives;
-using Microsoft.Generator.CSharp.SourceInput;
 using Microsoft.Generator.CSharp.Statements;
 
 namespace Microsoft.Generator.CSharp.Providers
@@ -151,23 +150,6 @@ private TypeSignatureModifiers GetDeclarationModifiersInternal()
 
         protected virtual PropertyProvider[] BuildProperties() => [];
 
-        private HashSet<string> BuildPropertyNames()
-        {
-            var propertyNames = new HashSet<string>();
-            foreach (var property in Properties)
-            {
-                propertyNames.Add(property.Name);
-                foreach (var attribute in property.Attributes ?? [])
-                {
-                    if (CodeGenAttributes.TryGetCodeGenMemberAttributeValue(attribute, out var name))
-                    {
-                        propertyNames.Add(name);
-                    }
-                }
-            }
-            return propertyNames;
-        }
-
         protected virtual FieldProvider[] BuildFields() => [];
 
         protected virtual CSharpType[] BuildImplements() => [];

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

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License.
 
+using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.Generator.CSharp.Input;
 using Microsoft.Generator.CSharp.Primitives;
@@ -202,5 +203,45 @@ public async Task CanChangeExtensibleEnumToEnum()
             Assert.AreEqual("Val2", enumProvider.EnumValues[1].Name);
             Assert.AreEqual("Val3", enumProvider.EnumValues[2].Name);
         }
+
+        [Test]
+        public async Task CanAddProperties()
+        {
+            await MockHelpers.LoadMockPluginAsync(compilation: async () => await Helpers.GetCompilationFromDirectoryAsync());
+
+            var props = new[]
+            {
+                InputFactory.Property("Prop1", InputFactory.Array(InputPrimitiveType.String))
+            };
+
+            var inputModel = InputFactory.Model("mockInputModel", properties: props);
+            var modelTypeProvider = new ModelProvider(inputModel);
+            var customCodeView = modelTypeProvider.CustomCodeView;
+
+            AssertCommon(customCodeView, modelTypeProvider, "Sample.Models", "MockInputModel");
+
+            // the custom properties shouldn't be added to the model provider
+            Assert.AreEqual(1, modelTypeProvider.Properties.Count);
+            Assert.AreEqual("Prop1", modelTypeProvider.Properties[0].Name);
+
+            // the custom properties shouldn't be parameters of the model's ctor
+            var modelCtors = modelTypeProvider.Constructors;
+            foreach (var ctor in modelCtors)
+            {
+                Assert.IsFalse(ctor.Signature.Parameters.Any(p => p.Name == "newProperty" || p.Name == "newProperty2"));
+            }
+
+            // the custom properties should be added to the custom code view
+            Assert.AreEqual(2, customCodeView!.Properties.Count);
+            Assert.AreEqual("NewProperty", customCodeView.Properties[0].Name);
+            Assert.AreEqual(new CSharpType(typeof(int)), customCodeView.Properties[0].Type);
+            Assert.AreEqual(MethodSignatureModifiers.Public, customCodeView.Properties[0].Modifiers);
+            Assert.IsTrue(customCodeView.Properties[0].Body.HasSetter);
+
+            Assert.AreEqual("NewProperty2", customCodeView.Properties[1].Name);
+            Assert.AreEqual(new CSharpType(typeof(string)), customCodeView.Properties[1].Type);
+            Assert.AreEqual(MethodSignatureModifiers.Public, customCodeView.Properties[1].Modifiers);
+            Assert.IsFalse(customCodeView.Properties[1].Body.HasSetter);
+        }
     }
 }

packages/http-client-csharp/generator/Microsoft.Generator.CSharp/test/Providers/ModelProviders/TestData/ModelCustomizationTests/CanAddProperties/MockInputModel.cs

@@ -0,0 +1,9 @@
+#nullable disable
+
+namespace Sample.Models;
+
+internal partial class MockInputModel
+{
+    public int NewProperty { get; set; }
+    public string NewProperty2 { get; }
+}