Support customizing model factory accessibility

packages/http-client-csharp/generator/Microsoft.Generator.CSharp/src/PostProcessing/PostProcessor.cs

@@ -176,13 +176,16 @@ private async Task<Project> RemoveMethodsFromModelFactoryAsync(Project project,
             // find the GENERATED document of model factory (we may have the customized document of this for overloads)
             Document? modelFactoryGeneratedDocument = null;
             // the nodes corresponding to the model factory symbol has never been changed therefore the nodes inside the cache are still usable
-            foreach (var declarationNode in definitions.DeclaredNodesCache[modelFactorySymbol])
+            if (definitions.DeclaredNodesCache.TryGetValue(modelFactorySymbol, out var nodes))
             {
-                var document = project.GetDocument(declarationNode.SyntaxTree);
-                if (document != null && GeneratedCodeWorkspace.IsGeneratedDocument(document))
+                foreach (var declarationNode in nodes)
                 {
-                    modelFactoryGeneratedDocument = document;
-                    break;
+                    var document = project.GetDocument(declarationNode.SyntaxTree);
+                    if (document != null && GeneratedCodeWorkspace.IsGeneratedDocument(document))
+                    {
+                        modelFactoryGeneratedDocument = document;
+                        break;
+                    }
                 }
             }
 

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

@@ -52,7 +52,12 @@ protected override string BuildName()
         protected override string BuildRelativeFilePath() => Path.Combine("src", "Generated", $"{Name}.cs");
 
         protected override TypeSignatureModifiers GetDeclarationModifiers()
-            => TypeSignatureModifiers.Static | TypeSignatureModifiers.Public | TypeSignatureModifiers.Class | TypeSignatureModifiers.Partial;
+        {
+            var customModifiers = GetCustomCodeModifiers();
+            return customModifiers != TypeSignatureModifiers.None
+                ? customModifiers
+                : TypeSignatureModifiers.Public | TypeSignatureModifiers.Static | TypeSignatureModifiers.Class | TypeSignatureModifiers.Partial;
+        }
 
         protected override string GetNamespace() => CodeModelPlugin.Instance.Configuration.ModelNamespace;
 

packages/http-client-csharp/generator/Microsoft.Generator.CSharp/test/Providers/ModelFactories/ModelFactoriesCustomizationTests.cs

@@ -3,7 +3,9 @@
 
 using System.Linq;
 using System.Threading.Tasks;
+using Microsoft.CodeAnalysis;
 using Microsoft.Generator.CSharp.Input;
+using Microsoft.Generator.CSharp.Primitives;
 using Microsoft.Generator.CSharp.Providers;
 using Microsoft.Generator.CSharp.Tests.Common;
 using NUnit.Framework;
@@ -37,6 +39,10 @@ public async Task CanReplaceModelMethod()
             var modelFactory = plugin.Object.OutputLibrary.TypeProviders.SingleOrDefault(t => t is ModelFactoryProvider);
             Assert.IsNotNull(modelFactory);
 
+            // The model factory should be public
+            Assert.IsTrue(modelFactory!.DeclarationModifiers.HasFlag(TypeSignatureModifiers.Public));
+            ValidateModelFactoryCommon(modelFactory);
+
             // The model factory method should be replaced
             var modelFactoryMethods = modelFactory!.Methods;
             Assert.AreEqual(1, modelFactoryMethods.Count);
@@ -71,9 +77,50 @@ public async Task DoesNotReplaceMethodIfNotCustomized()
             var modelFactory = plugin.Object.OutputLibrary.TypeProviders.SingleOrDefault(t => t is ModelFactoryProvider);
             Assert.IsNotNull(modelFactory);
 
+            // The model factory should be public
+            Assert.IsTrue(modelFactory!.DeclarationModifiers.HasFlag(TypeSignatureModifiers.Public));
+            ValidateModelFactoryCommon(modelFactory);
+
             // The model factory method should not be replaced
             var modelFactoryMethods = modelFactory!.Methods;
             Assert.AreEqual(1, modelFactoryMethods.Count);
         }
+
+        private static void ValidateModelFactoryCommon(TypeProvider modelFactory)
+        {
+            Assert.IsTrue(modelFactory!.DeclarationModifiers.HasFlag(TypeSignatureModifiers.Static));
+            Assert.IsTrue(modelFactory!.DeclarationModifiers.HasFlag(TypeSignatureModifiers.Partial));
+            Assert.IsTrue(modelFactory!.DeclarationModifiers.HasFlag(TypeSignatureModifiers.Class));
+        }
+
+        [Test]
+        public async Task CanChangeAccessibilityOfModelFactory()
+        {
+            var plugin = await MockHelpers.LoadMockPluginAsync(
+                inputModelTypes: [
+                    InputFactory.Model(
+                        "mockInputModel",
+                        properties:
+                        [
+                            InputFactory.Property("Prop1", InputPrimitiveType.String),
+                            InputFactory.Property("OptionalBool", InputPrimitiveType.Boolean, isRequired: false)
+                        ]),
+                    InputFactory.Model(
+                        "otherModel",
+                        properties: [InputFactory.Property("Prop2", InputPrimitiveType.String)]),
+                ],
+                compilation: async () => await Helpers.GetCompilationFromDirectoryAsync());
+            var csharpGen = new CSharpGen();
+
+            await csharpGen.ExecuteAsync();
+
+            // Find the model factory provider
+            var modelFactory = plugin.Object.OutputLibrary.TypeProviders.SingleOrDefault(t => t is ModelFactoryProvider);
+            Assert.IsNotNull(modelFactory);
+
+            // The model factory should be internal
+            Assert.IsTrue(modelFactory!.DeclarationModifiers.HasFlag(TypeSignatureModifiers.Internal));
+            ValidateModelFactoryCommon(modelFactory);
+        }
     }
 }

packages/http-client-csharp/generator/Microsoft.Generator.CSharp/test/Providers/ModelFactories/TestData/ModelFactoriesCustomizationTests/CanChangeAccessibilityOfModelFactory/SampleNamespaceModelFactory.cs

@@ -0,0 +1,9 @@
+using Microsoft.Generator.CSharp.Customization;
+using System;
+
+namespace Sample.Models
+{
+    internal static partial class SampleNamespaceModelFactory
+    {
+    }
+}