implement the feature of changing the name of a model (#4285)

Fixes #4256 
Fixes #4261

In order to get our mocking system working properly and make everything
aligned, I changed the `SourceInputModel` to public and added it to the
`CodeModelPlugin` so that our plugin writers could override something on
it to do some advanced stuffs

packages/http-client-csharp/generator/Microsoft.Generator.CSharp.ClientModel/test/TestHelpers/MockHelpers.cs

@@ -5,10 +5,12 @@ using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Reflection;
+using Microsoft.CodeAnalysis;
 using Microsoft.Generator.CSharp.ClientModel.Providers;
 using Microsoft.Generator.CSharp.Input;
 using Microsoft.Generator.CSharp.Primitives;
 using Microsoft.Generator.CSharp.Providers;
+using Microsoft.Generator.CSharp.SourceInput;
 using Moq;
 using Moq.Protected;
 
@@ -96,6 +98,9 @@ namespace Microsoft.Generator.CSharp.ClientModel.Tests
                 mockPluginInstance.Setup(p => p.InputLibrary).Returns(createInputLibrary);
             }
 
+            var sourceInputModel = new Mock<SourceInputModel>(() => new SourceInputModel(null)) { CallBase = true };
+            mockPluginInstance.Setup(p => p.SourceInputModel).Returns(sourceInputModel.Object);
+
             codeModelInstance!.SetValue(null, mockPluginInstance.Object);
             clientModelInstance!.SetValue(null, mockPluginInstance.Object);
             mockPluginInstance.Object.Configure();

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

@@ -7,6 +7,7 @@ using System.IO;
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.Generator.CSharp.Primitives;
+using Microsoft.Generator.CSharp.SourceInput;
 
 namespace Microsoft.Generator.CSharp
 {
@@ -14,7 +15,6 @@ namespace Microsoft.Generator.CSharp
     {
         private const string ConfigurationFileName = "Configuration.json";
         private const string CodeModelFileName = "tspCodeModel.json";
-        private const string GeneratedFolderName = "Generated";
 
         private static readonly string[] _filesToKeep = [ConfigurationFileName, CodeModelFileName];
 
@@ -25,10 +25,11 @@ namespace Microsoft.Generator.CSharp
         {
             GeneratedCodeWorkspace.Initialize();
             var outputPath = CodeModelPlugin.Instance.Configuration.OutputDirectory;
-            var generatedSourceOutputPath = ParseGeneratedSourceOutputPath(outputPath);
-            var generatedTestOutputPath = Path.Combine(outputPath, "..", "..", "tests", GeneratedFolderName);
+            var generatedSourceOutputPath = CodeModelPlugin.Instance.Configuration.ProjectGeneratedDirectory;
+            var generatedTestOutputPath = CodeModelPlugin.Instance.Configuration.TestGeneratedDirectory;
 
             GeneratedCodeWorkspace workspace = await GeneratedCodeWorkspace.Create();
+            await CodeModelPlugin.Instance.InitializeSourceInputModelAsync();
 
             var output = CodeModelPlugin.Instance.OutputLibrary;
             Directory.CreateDirectory(Path.Combine(generatedSourceOutputPath, "Models"));
@@ -82,23 +83,6 @@ namespace Microsoft.Generator.CSharp
             }
         }
 
-        /// <summary>
-        /// Parses and updates the output path for the generated code.
-        /// </summary>
-        /// <param name="outputPath">The output path.</param>
-        /// <returns>The parsed output path string.</returns>
-        internal static string ParseGeneratedSourceOutputPath(string outputPath)
-        {
-            if (!outputPath.EndsWith("src", StringComparison.Ordinal) && !outputPath.EndsWith("src/", StringComparison.Ordinal))
-            {
-                outputPath = Path.Combine(outputPath, "src");
-            }
-
-            outputPath = Path.Combine(outputPath, GeneratedFolderName);
-
-            return outputPath;
-        }
-
         /// <summary>
         /// Clears the output directory specified by <paramref name="path"/>. If <paramref name="filesToKeep"/> is not null,
         /// the specified files in the output directory will not be deleted.

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

@@ -4,10 +4,12 @@
 using System;
 using System.Collections.Generic;
 using System.ComponentModel.Composition;
+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.SourceInput;
 
 namespace Microsoft.Generator.CSharp
 {
@@ -53,11 +55,11 @@ namespace Microsoft.Generator.CSharp
         }
 
         internal bool IsNewProject { get; set; }
-
         private Lazy<InputLibrary> _inputLibrary;
 
         // Extensibility points to be implemented by a plugin
         public virtual TypeFactory TypeFactory { get; }
+        public virtual SourceInputModel SourceInputModel => _sourceInputModel ?? throw new InvalidOperationException($"SourceInputModel has not been initialized yet");
         public virtual string LicenseString => string.Empty;
         public virtual OutputLibrary OutputLibrary { get; } = new();
         public virtual InputLibrary InputLibrary => _inputLibrary.Value;
@@ -72,5 +74,12 @@ namespace Microsoft.Generator.CSharp
         {
             _visitors.Add(visitor);
         }
+
+        private SourceInputModel? _sourceInputModel;
+        internal async Task InitializeSourceInputModelAsync()
+        {
+            GeneratedCodeWorkspace existingCode = GeneratedCodeWorkspace.CreateExistingCodeProject(Instance.Configuration.ProjectDirectory, Instance.Configuration.ProjectGeneratedDirectory);
+            _sourceInputModel =  new SourceInputModel(await existingCode.GetCompilationAsync());
+        }
     }
 }

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

@@ -20,6 +20,7 @@ namespace Microsoft.Generator.CSharp
             "Enum",
         ];
 
+        private const string GeneratedFolderName = "Generated";
         private const string ConfigurationFileName = "Configuration.json";
 
         // for mocking
@@ -144,6 +145,15 @@ namespace Microsoft.Generator.CSharp
         private string? _projectDirectory;
         internal string ProjectDirectory => _projectDirectory ??= Path.Combine(OutputDirectory, "src");
 
+        private string? _testProjectDirectory;
+        internal string TestProjectDirectory => _testProjectDirectory ??= Path.Combine(OutputDirectory, "tests");
+
+        private string? _projectGeneratedDirectory;
+        internal string ProjectGeneratedDirectory => _projectGeneratedDirectory ??= Path.Combine(ProjectDirectory, GeneratedFolderName);
+
+        private string? _testGeneratedDirectory;
+        internal string TestGeneratedDirectory => _testGeneratedDirectory ??= Path.Combine(TestProjectDirectory, GeneratedFolderName);
+
         internal string LibraryName { get; }
 
         /// <summary>

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

@@ -47,6 +47,14 @@ namespace Microsoft.Generator.CSharp
             _cachedProject = Task.Run(CreateGeneratedCodeProject);
         }
 
+        internal async Task<CSharpCompilation> GetCompilationAsync()
+        {
+            var compilation = await _project.GetCompilationAsync();
+            Debug.Assert(compilation is CSharpCompilation);
+
+            return (CSharpCompilation)compilation;
+        }
+
         public void AddPlainFiles(string name, string content)
         {
             PlainFiles.Add(name, content);
@@ -140,17 +148,18 @@ namespace Microsoft.Generator.CSharp
             return new GeneratedCodeWorkspace(generatedCodeProject);
         }
 
-        public static GeneratedCodeWorkspace CreateExistingCodeProject(string outputDirectory)
+        internal static GeneratedCodeWorkspace CreateExistingCodeProject(string projectDirectory, string generatedDirectory)
         {
             var workspace = new AdhocWorkspace();
             var newOptionSet = workspace.Options.WithChangedOption(FormattingOptions.NewLine, LanguageNames.CSharp, _newLine);
             workspace.TryApplyChanges(workspace.CurrentSolution.WithOptions(newOptionSet));
             Project project = workspace.AddProject("ExistingCode", LanguageNames.CSharp);
 
-            if (Path.IsPathRooted(outputDirectory))
+            if (Path.IsPathRooted(projectDirectory))
             {
-                outputDirectory = Path.GetFullPath(outputDirectory);
-                project = AddDirectory(project, outputDirectory, null);
+                projectDirectory = Path.GetFullPath(projectDirectory);
+
+                project = AddDirectory(project, projectDirectory, skipPredicate: sourceFile => sourceFile.StartsWith(generatedDirectory));
             }
 
             project = project
@@ -161,7 +170,7 @@ namespace Microsoft.Generator.CSharp
             return new GeneratedCodeWorkspace(project);
         }
 
-        public static async Task<Compilation?> CreatePreviousContractFromDll(string xmlDocumentationpath, string dllPath)
+        internal static async Task<Compilation?> CreatePreviousContractFromDll(string xmlDocumentationpath, string dllPath)
         {
             var workspace = new AdhocWorkspace();
             Project project = workspace.AddProject("PreviousContract", LanguageNames.CSharp);

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

@@ -6,13 +6,12 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Xml.Linq;
 using Microsoft.CodeAnalysis;
-using Microsoft.Generator.CSharp.Expressions;
 using Microsoft.Generator.CSharp.Primitives;
 using Microsoft.Generator.CSharp.Statements;
 
 namespace Microsoft.Generator.CSharp.Providers
 {
-    public class NamedTypeSymbolProvider : TypeProvider
+    internal sealed class NamedTypeSymbolProvider : TypeProvider
     {
         private INamedTypeSymbol _namedTypeSymbol;
 
@@ -21,6 +20,8 @@ namespace Microsoft.Generator.CSharp.Providers
             _namedTypeSymbol = namedTypeSymbol;
         }
 
+        private protected sealed override TypeProvider? GetCustomCodeView() => null;
+
         protected override string BuildRelativeFilePath() => throw new InvalidOperationException("This type should not be writting in generation");
 
         protected override string BuildName() => _namedTypeSymbol.Name;

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

@@ -12,6 +12,17 @@ namespace Microsoft.Generator.CSharp.Providers
 {
     public abstract class TypeProvider
     {
+        private Lazy<TypeProvider?> _customCodeView;
+        protected TypeProvider()
+        {
+            _customCodeView = new(GetCustomCodeView);
+        }
+
+        private protected virtual TypeProvider? GetCustomCodeView()
+            => CodeModelPlugin.Instance.SourceInputModel.FindForType(GetNamespace(), BuildName());
+
+        public TypeProvider? CustomCodeView => _customCodeView.Value;
+
         protected string? _deprecated;
 
         /// <summary>
@@ -22,7 +33,7 @@ namespace Microsoft.Generator.CSharp.Providers
 
         private string? _relativeFilePath;
 
-        public string Name => _name ??= BuildName();
+        public string Name => _name ??= CustomCodeView?.Name ?? BuildName();
 
         private string? _name;
 
@@ -45,7 +56,7 @@ namespace Microsoft.Generator.CSharp.Providers
         private CSharpType? _type;
         public CSharpType Type => _type ??= new(
             this,
-            GetNamespace(),
+            CustomCodeView?.GetNamespace() ?? GetNamespace(),
             GetTypeArguments(),
             GetBaseType());
 

packages/http-client-csharp/generator/Microsoft.Generator.CSharp/src/SourceInput/ClientSourceInput.cs

@@ -1,9 +0,0 @@
-// Copyright (c) Microsoft Corporation. All rights reserved.
-// Licensed under the MIT License.
-
-using Microsoft.CodeAnalysis;
-
-namespace Microsoft.Generator.CSharp.SourceInput
-{
-    internal record ClientSourceInput(INamedTypeSymbol? ParentClientType);
-}

packages/http-client-csharp/generator/Microsoft.Generator.CSharp/src/SourceInput/CompilationCustomCode.cs

@@ -1,21 +0,0 @@
-// Copyright (c) Microsoft Corporation. All rights reserved.
-// Licensed under the MIT License.
-
-using System.Collections.Generic;
-using Microsoft.CodeAnalysis;
-using Microsoft.Generator.CSharp.Primitives;
-
-namespace Microsoft.Generator.CSharp.SourceInput
-{
-    internal abstract class CompilationCustomCode
-    {
-        protected Compilation _compilation;
-
-        public CompilationCustomCode(Compilation compilation)
-        {
-            _compilation = compilation;
-        }
-
-        internal abstract IMethodSymbol? FindMethod(string namespaceName, string typeName, string methodName, IEnumerable<CSharpType> parameters);
-    }
-}

packages/http-client-csharp/generator/Microsoft.Generator.CSharp/src/SourceInput/ModelTypeMapping.cs

@@ -1,96 +0,0 @@
-// Copyright (c) Microsoft Corporation. All rights reserved.
-// Licensed under the MIT License.
-
-using System.Collections.Generic;
-using Microsoft.CodeAnalysis;
-
-namespace Microsoft.Generator.CSharp.SourceInput
-{
-    internal class ModelTypeMapping
-    {
-        private readonly Dictionary<string, ISymbol> _propertyMappings;
-        private readonly Dictionary<string, ISymbol> _codeGenMemberMappings;
-        private readonly Dictionary<string, SourcePropertySerializationMapping> _typeSerializationMappings;
-
-        public string[]? Usages { get; }
-        public string[]? Formats { get; }
-
-        public ModelTypeMapping(CodeGenAttributes codeGenAttributes, INamedTypeSymbol existingType)
-        {
-            _propertyMappings = new();
-            _codeGenMemberMappings = new();
-            _typeSerializationMappings = new();
-
-            foreach (ISymbol member in GetMembers(existingType))
-            {
-                // If member is defined in both base and derived class, use derived one
-                if (ShouldIncludeMember(member) && !_propertyMappings.ContainsKey(member.Name))
-                {
-                    _propertyMappings[member.Name] = member;
-                }
-
-                foreach (var attributeData in member.GetAttributes())
-                {
-                    // handle CodeGenMember attribute
-                    if (codeGenAttributes.TryGetCodeGenMemberAttributeValue(attributeData, out var schemaMemberName))
-                    {
-                        _codeGenMemberMappings[schemaMemberName] = member;
-                    }
-                }
-            }
-
-            foreach (var attributeData in existingType.GetAttributes())
-            {
-                // handle CodeGenModel attribute
-                if (codeGenAttributes.TryGetCodeGenModelAttributeValue(attributeData, out var usage, out var formats))
-                {
-                    Usages = usage;
-                    Formats = formats;
-                }
-
-                // handle CodeGenSerialization attribute
-                if (codeGenAttributes.TryGetCodeGenSerializationAttributeValue(attributeData, out var propertyName, out var serializationNames, out var serializationHook, out var deserializationHook, out var bicepSerializationHook) && !_typeSerializationMappings.ContainsKey(propertyName))
-                {
-                    _typeSerializationMappings.Add(propertyName, new(propertyName, serializationNames, serializationHook, deserializationHook, bicepSerializationHook));
-                }
-            }
-        }
-
-        private static bool ShouldIncludeMember(ISymbol member)
-        {
-            // here we exclude those "CompilerGenerated" members, such as the backing field of a property which is also a field.
-            return !member.IsImplicitlyDeclared && member is IPropertySymbol or IFieldSymbol;
-        }
-
-        public ISymbol? GetMemberByOriginalName(string name)
-            => _codeGenMemberMappings.TryGetValue(name, out var renamedSymbol) ?
-                renamedSymbol :
-                _propertyMappings.TryGetValue(name, out var memberSymbol) ? memberSymbol : null;
-
-        internal SourcePropertySerializationMapping? GetForMemberSerialization(string name)
-            => _typeSerializationMappings.TryGetValue(name, out var serialization) ? serialization : null;
-
-        public IEnumerable<ISymbol> GetPropertiesWithSerialization()
-        {
-            // only the property with CodeGenSerialization attribute will be emitted into the serialization code.
-            foreach (var (propertyName, symbol) in _propertyMappings)
-            {
-                if (_typeSerializationMappings.ContainsKey(propertyName))
-                    yield return symbol;
-            }
-        }
-
-        private static IEnumerable<ISymbol> GetMembers(INamedTypeSymbol? typeSymbol)
-        {
-            while (typeSymbol != null)
-            {
-                foreach (var symbol in typeSymbol.GetMembers())
-                {
-                    yield return symbol;
-                }
-
-                typeSymbol = typeSymbol.BaseType;
-            }
-        }
-    }
-}

packages/http-client-csharp/generator/Microsoft.Generator.CSharp/src/SourceInput/SourceInputModel.cs

@@ -9,38 +9,38 @@ using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.Build.Construction;
 using Microsoft.CodeAnalysis;
-using Microsoft.Generator.CSharp.Customization;
-using Microsoft.Generator.CSharp.Primitives;
 using Microsoft.Generator.CSharp.Providers;
 using NuGet.Configuration;
 
 namespace Microsoft.Generator.CSharp.SourceInput
 {
-    internal sealed class SourceInputModel
+    public class SourceInputModel
     {
-        private static SourceInputModel? _instance;
-        public static SourceInputModel Instance => _instance ?? throw new InvalidOperationException("SourceInputModel has not been initialized");
-
-        public static void Initialize(Compilation customization, CompilationCustomCode? existingCompilation = null)
-        {
-            _instance = new SourceInputModel(customization, existingCompilation);
-        }
-
-        private readonly CompilationCustomCode? _existingCompilation;
         private readonly CodeGenAttributes _codeGenAttributes;
-        private readonly Dictionary<string, INamedTypeSymbol> _nameMap = new Dictionary<string, INamedTypeSymbol>(StringComparer.OrdinalIgnoreCase);
 
-        public Compilation Customization { get; }
-        public Compilation? PreviousContract { get; }
+        public Compilation? Customization { get; }
+        private Lazy<Compilation?> _previousContract;
+        public Compilation? PreviousContract => _previousContract.Value;
 
-        private SourceInputModel(Compilation customization, CompilationCustomCode? existingCompilation = null)
+        private readonly Lazy<IReadOnlyDictionary<string, INamedTypeSymbol>> _nameMap;
+
+        public SourceInputModel(Compilation? customization)
         {
             Customization = customization;
-            PreviousContract = LoadBaselineContract().GetAwaiter().GetResult();
-            _existingCompilation = existingCompilation;
+            _previousContract = new(() => LoadBaselineContract().GetAwaiter().GetResult());
 
             _codeGenAttributes = new CodeGenAttributes();
 
+            _nameMap = new(PopulateNameMap);
+        }
+
+        private IReadOnlyDictionary<string, INamedTypeSymbol> PopulateNameMap()
+        {
+            var nameMap = new Dictionary<string, INamedTypeSymbol>();
+            if (Customization == null)
+            {
+                return nameMap;
+            }
             IAssemblySymbol assembly = Customization.Assembly;
 
             foreach (IModuleSymbol module in assembly.Modules)
@@ -49,75 +49,28 @@ namespace Microsoft.Generator.CSharp.SourceInput
                 {
                     if (type is INamedTypeSymbol namedTypeSymbol && TryGetName(type, out var schemaName))
                     {
-                        _nameMap.Add(schemaName, namedTypeSymbol);
+                        nameMap.Add(schemaName, namedTypeSymbol);
                     }
                 }
             }
+
+            return nameMap;
         }
 
-        public IReadOnlyList<string>? GetServiceVersionOverrides()
+        public TypeProvider? FindForType(string ns, string name)
         {
-            var osvAttributeType = Customization.GetTypeByMetadataName(typeof(CodeGenOverrideServiceVersionsAttribute).FullName!)!;
-            var osvAttribute = Customization.Assembly.GetAttributes()
-                .FirstOrDefault(a => SymbolEqualityComparer.Default.Equals(a.AttributeClass, osvAttributeType));
-
-            return osvAttribute?.ConstructorArguments[0].Values.Select(v => v.Value).OfType<string>().ToList();
-        }
-
-        internal ModelTypeMapping? CreateForModel(INamedTypeSymbol? symbol)
-        {
-            if (symbol == null)
+            if (Customization == null)
+            {
                 return null;
-
-            return new ModelTypeMapping(_codeGenAttributes, symbol);
-        }
-
-        internal IMethodSymbol? FindMethod(string namespaceName, string typeName, string methodName, IEnumerable<CSharpType> parameters)
-        {
-            return _existingCompilation?.FindMethod(namespaceName, typeName, methodName, parameters);
-        }
-
-        public INamedTypeSymbol? FindForType(string name)
-        {
-            var ns = CodeModelPlugin.Instance.Configuration.ModelNamespace;
+            }
             var fullyQualifiedMetadataName = $"{ns}.{name}";
-            if (!_nameMap.TryGetValue(name, out var type) &&
-                !_nameMap.TryGetValue(fullyQualifiedMetadataName, out type))
+            if (!_nameMap.Value.TryGetValue(name, out var type) &&
+                !_nameMap.Value.TryGetValue(fullyQualifiedMetadataName, out type))
             {
                 type = Customization.Assembly.GetTypeByMetadataName(fullyQualifiedMetadataName);
             }
 
-            return type;
-        }
-
-        internal bool TryGetClientSourceInput(INamedTypeSymbol type, [NotNullWhen(true)] out ClientSourceInput? clientSourceInput)
-        {
-            foreach (var attribute in type.GetAttributes())
-            {
-                var attributeType = attribute.AttributeClass;
-                while (attributeType != null)
-                {
-                    if (attributeType.Name == CodeGenAttributes.CodeGenClientAttributeName)
-                    {
-                        INamedTypeSymbol? parentClientType = null;
-                        foreach ((var argumentName, TypedConstant constant) in attribute.NamedArguments)
-                        {
-                            if (argumentName == nameof(CodeGenClientAttribute.ParentClient))
-                            {
-                                parentClientType = (INamedTypeSymbol?)constant.Value;
-                            }
-                        }
-
-                        clientSourceInput = new ClientSourceInput(parentClientType);
-                        return true;
-                    }
-
-                    attributeType = attributeType.BaseType;
-                }
-            }
-
-            clientSourceInput = null;
-            return false;
+            return type != null ? new NamedTypeSymbolProvider(type) : null;
         }
 
         private bool TryGetName(ISymbol symbol, [NotNullWhen(true)] out string? name)

packages/http-client-csharp/generator/Microsoft.Generator.CSharp/test/CSharpGenTests.cs

@@ -10,33 +10,6 @@ namespace Microsoft.Generator.CSharp.Tests
 {
     public class CSharpGenTests
     {
-        // Validates that the output path is parsed correctly when provided
-        [Test]
-        public void TestGetOutputPath_OutputPathProvided()
-        {
-            var outputPath = "./outputDir";
-            var parsedOutputPath = CSharpGen.ParseGeneratedSourceOutputPath(outputPath);
-            var expectedPath = Path.Combine(outputPath, "src", "Generated");
-            var areEqual = string.Equals(expectedPath, parsedOutputPath, StringComparison.OrdinalIgnoreCase);
-
-            Assert.IsTrue(areEqual);
-
-            // append 'src' to the output path and validate that it is not appended again
-            TestOutputPathAppended(outputPath, expectedPath);
-        }
-
-        // Validates that the output path is parsed correctly when an empty string is provided
-        [Test]
-        public void TestGetConfigurationInputFilePath_DefaultPath()
-        {
-            var outputPath = "";
-            var parsedOutputPath = CSharpGen.ParseGeneratedSourceOutputPath(outputPath);
-            var expectedPath = Path.Combine("src", "Generated");
-            var areEqual = string.Equals(expectedPath, parsedOutputPath, StringComparison.OrdinalIgnoreCase);
-
-            Assert.IsTrue(areEqual);
-        }
-
         // Validates that a valid plugin implementation is accepted
         [Test]
         public void TestCSharpGen_ValidPlugin()
@@ -61,19 +34,5 @@ namespace Microsoft.Generator.CSharp.Tests
             mockPlugin.Verify(m => m.Visitors, Times.Once);
             mockVisitor.Verify(m => m.Visit(mockPlugin.Object.OutputLibrary), Times.Once);
         }
-
-        private void TestOutputPathAppended(string outputPath, string expectedPath)
-        {
-            var srcPath = "src";
-
-            outputPath = Path.Combine(outputPath, srcPath);
-
-
-            var parsedOutputPath = CSharpGen.ParseGeneratedSourceOutputPath(outputPath);
-
-            var areEqual = string.Equals(expectedPath, parsedOutputPath, StringComparison.OrdinalIgnoreCase);
-
-            Assert.IsTrue(areEqual);
-        }
     }
 }

packages/http-client-csharp/generator/Microsoft.Generator.CSharp/test/ConfigurationTests.cs

@@ -49,10 +49,9 @@ namespace Microsoft.Generator.CSharp.Tests
         }
 
         // Validates that the output folder is parsed correctly from the configuration
-        [TestCaseSource("ParseConfigOutputFolderTestCases")]
+        [TestCaseSource(nameof(ParseConfigOutputFolderTestCases))]
         public void TestParseConfig_OutputFolder(string mockJson, bool throwsError)
         {
-
             var expected = Path.GetFullPath(MockHelpers.TestHelpersFolder);
 
             if (throwsError)
@@ -64,6 +63,8 @@ namespace Microsoft.Generator.CSharp.Tests
             var configuration = Configuration.Load(MockHelpers.TestHelpersFolder, mockJson);
 
             Assert.AreEqual(expected, configuration.OutputDirectory);
+            Assert.AreEqual(Path.Combine(expected, "src", "Generated"), configuration.ProjectGeneratedDirectory);
+            Assert.AreEqual(Path.Combine(expected, "tests", "Generated"), configuration.TestGeneratedDirectory);
         }
 
         // Validates that the LibraryName field is parsed correctly from the configuration

packages/http-client-csharp/generator/Microsoft.Generator.CSharp/test/Helpers.cs

@@ -1,8 +1,11 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License.
 
+using System;
 using System.Diagnostics;
 using System.IO;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis;
 
 namespace Microsoft.Generator.CSharp.Tests
 {
@@ -11,15 +14,47 @@ namespace Microsoft.Generator.CSharp.Tests
         private static readonly string _assemblyLocation = Path.GetDirectoryName(typeof(Helpers).Assembly.Location)!;
 
         public static string GetExpectedFromFile(string? parameters = null)
+        {
+            return File.ReadAllText(GetAssetFilePath(parameters));
+        }
+
+        private static string GetAssetFilePath(string? parameters = null)
         {
             var stackTrace = new StackTrace();
-            var stackFrame = stackTrace.GetFrame(1);
-            var method = stackFrame!.GetMethod();
+            var stackFrame = GetRealMethodInvocation(stackTrace);
+            var method = stackFrame.GetMethod();
             var callingClass = method!.DeclaringType;
             var nsSplit = callingClass!.Namespace!.Split('.');
-            var ns = nsSplit[nsSplit.Length - 1];
+            var ns = nsSplit[^1];
             var paramString = parameters is null ? string.Empty : $"({parameters})";
-            return File.ReadAllText(Path.Combine(_assemblyLocation, ns, "TestData", callingClass.Name, $"{method.Name}{paramString}.cs"));
+            return Path.Combine(_assemblyLocation, ns, "TestData", callingClass.Name, $"{method.Name}{paramString}.cs");
+        }
+
+        private static StackFrame GetRealMethodInvocation(StackTrace stackTrace)
+        {
+            int i = 1;
+            while (i < stackTrace.FrameCount)
+            {
+                var frame = stackTrace.GetFrame(i);
+                if (frame!.GetMethod()!.DeclaringType != typeof(Helpers))
+                {
+                    return frame;
+                }
+                i++;
+            }
+
+            throw new InvalidOperationException($"There is no method invocation outside the {typeof(Helpers)} class in the stack trace");
+        }
+
+        public static Compilation GetCompilationFromFile(string? parameters = null)
+        {
+            SyntaxTree syntaxTree = CSharpSyntaxTree.ParseText(File.ReadAllText(GetAssetFilePath(parameters)));
+            CSharpCompilation compilation = CSharpCompilation.Create("ExistingCode")
+                .WithOptions(new CSharpCompilationOptions(OutputKind.ConsoleApplication))
+                .AddReferences(MetadataReference.CreateFromFile(typeof(object).Assembly.Location))
+                .AddSyntaxTrees(syntaxTree);
+
+            return compilation;
         }
     }
 }

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

@@ -0,0 +1,35 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+using Microsoft.Generator.CSharp.Input;
+using Microsoft.Generator.CSharp.Providers;
+using Microsoft.Generator.CSharp.Tests.Common;
+using NUnit.Framework;
+
+namespace Microsoft.Generator.CSharp.Tests.Providers // the namespace here is crucial to get correct test data file.
+{
+    public class ModelCustomizationTests
+    {
+        // Validates that the property body's setter is correctly set based on the property type
+        [TestCase]
+        public void TestCustomization_CanChangeModelName()
+        {
+            MockHelpers.LoadMockPlugin(customization: Helpers.GetCompilationFromFile());
+
+            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;
+
+            Assert.IsNotNull(customCodeView);
+            Assert.AreEqual("CustomizedModel", modelTypeProvider.Type.Name);
+            Assert.AreEqual("NewNamespace.Models", modelTypeProvider.Type.Namespace);
+            Assert.AreEqual(customCodeView?.Name, modelTypeProvider.Type.Name);
+            Assert.AreEqual(customCodeView?.Type.Namespace, modelTypeProvider.Type.Namespace);
+        }
+    }
+}

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

@@ -0,0 +1,25 @@
+#nullable disable
+
+using System;
+
+namespace NewNamespace
+{
+    // TODO: if we decide to use the public APIs, we do not have to define this attribute here. Tracking: https://github.com/Azure/autorest.csharp/issues/4551
+    [AttributeUsage(AttributeTargets.Class)]
+    internal class CodeGenTypeAttribute : Attribute
+    {
+        public string OriginalName { get; }
+
+        public CodeGenTypeAttribute(string originalName)
+        {
+            OriginalName = originalName;
+        }
+    }
+}
+namespace NewNamespace.Models
+{
+    [CodeGenType("MockInputModel")]
+    public partial class CustomizedModel
+    {
+    }
+}

packages/http-client-csharp/generator/Microsoft.Generator.CSharp/test/TestHelpers/MockHelpers.cs

@@ -1,14 +1,15 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License.
 
-using System.IO;
 using System;
-using System.Collections.Generic;
+using System.IO;
+using Microsoft.CodeAnalysis;
 using Microsoft.Generator.CSharp.Input;
 using Microsoft.Generator.CSharp.Primitives;
-using Moq.Protected;
-using Moq;
+using Microsoft.Generator.CSharp.SourceInput;
 using Microsoft.Generator.CSharp.Tests.Common;
+using Moq;
+using Moq.Protected;
 
 namespace Microsoft.Generator.CSharp.Tests
 {
@@ -20,7 +21,8 @@ namespace Microsoft.Generator.CSharp.Tests
             Func<InputType, CSharpType>? createCSharpTypeCore = null,
             Func<OutputLibrary>? createOutputLibrary = null,
             string? configuration = null,
-            InputModelType[]? inputModelTypes = null)
+            InputModelType[]? inputModelTypes = null,
+            Compilation? customization = null)
         {
             var configFilePath = Path.Combine(AppContext.BaseDirectory, TestHelpersFolder);
             // initialize the singleton instance of the plugin
@@ -47,7 +49,13 @@ namespace Microsoft.Generator.CSharp.Tests
 
             mockPlugin.SetupGet(p => p.TypeFactory).Returns(mockTypeFactory.Object);
 
+            var sourceInputModel = new Mock<SourceInputModel>(() => new SourceInputModel(customization)) { CallBase = true };
+
+            mockPlugin.Setup(p => p.SourceInputModel).Returns(sourceInputModel.Object);
+
             CodeModelPlugin.Instance = mockPlugin.Object;
+
+
             return mockPlugin;
         }
     }