Added support for unit testing the SGF Source Generators

README.md

@@ -208,6 +208,35 @@ public class MyGenerator : IncrementalGenerator
 }
 ```
 
+## Unit Tests 
+You can write unit test to validate that your source generators are working as expected. To do this for this library requires a very tiny amount of extra work. You can also look at the [example project](src\Sandbox\ConsoleApp.SourceGenerator.Tests\TestCase.cs) to see how it works. 
+
+The generated class will all be internal so your unit test assembly will need to have viability.
+
+```csharp
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("ConsoleApp.SourceGenerator.Tests")]
+```
+
+Then for your unit test functions the only difference will be that instead of creating an instance of your class you create an instance of the `Hoist` class.
+
+```c#
+// Create the instance of our generator and set whatever properties 
+ConsoleAppSourceGenerator generator = new ConsoleAppSourceGenerator()
+{
+    Explode = true
+};
+// Build the instance of the wrapper `Host` which takes in your generator.
+ConsoleAppSourceGeneratorHoist host = new
+
+// From here it's just like testing any other generator
+ConsoleAppSourceGeneratorHoist(generator);
+GeneratorDriver driver = CSharpGeneratorDriver.Create(host);
+driver = driver.RunGenerators(compilation);
+```
+The only unique feature is the wrapper class `{YourGeneratorName}Host`. This class is an internal feature of `SGF` and is used to make sure all dependencies are resolved before calling into your source generator. 
+
 ## Project Layout  
 
 This library is made up of quite a few different components leveraging various techniques to help

src/Sandbox/ConsoleApp.SourceGenerator.Tests/ConsoleApp.SourceGenerator.Tests.csproj

@@ -0,0 +1,28 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <LangVersion>12</LangVersion>
+
+    <IsPackable>false</IsPackable>
+    <IsTestProject>true</IsTestProject>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="coverlet.collector" Version="6.0.0" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
+    <PackageReference Include="xunit" Version="2.5.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.3" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\ConsoleApp.SourceGenerator\ConsoleApp.SourceGenerator.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+
+</Project>

src/Sandbox/ConsoleApp.SourceGenerator.Tests/TestCase.cs

@@ -0,0 +1,47 @@
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+
+namespace ConsoleApp.SourceGenerator.Tests
+{
+    public class TestCase
+    {
+        [Fact]
+        public void Compiles()
+        {
+            Compose("""
+                namespace MyNamespace
+                {
+                    public class MyClass
+                    {
+                    }
+                }
+                """);
+        }
+
+
+        private void Compose(string source)
+        {
+            // Create the generator, you can pass any parameters you want
+            ConsoleAppSourceGenerator generator = new ConsoleAppSourceGenerator()
+            {
+                WarningMessage = "I am running from a unit test!" // Change any settings you want
+            };
+            // Create the 'host' which is the wrapper that is auto generated by SGF. 
+            ConsoleAppSourceGeneratorHoist host = new ConsoleAppSourceGeneratorHoist(generator);
+            // Parse the source into syntax trees
+            SyntaxTree syntaxTree = CSharpSyntaxTree.ParseText(source);
+            // Setup the compilation settings
+            CSharpCompilation compilation = CSharpCompilation.Create(
+              assemblyName: "UniTests",
+              syntaxTrees: new[] { syntaxTree });
+            // Create the driver the executes the generator
+            GeneratorDriver driver = CSharpGeneratorDriver.Create(host);
+            // Run it 
+            driver = driver.RunGenerators(compilation);
+            // Get the results
+            GeneratorDriverRunResult results = driver.GetRunResult();
+            // Test the results
+            Assert.NotEmpty(results.GeneratedTrees);
+        }
+    }
+}

src/Sandbox/ConsoleApp.SourceGenerator/AssemblyInfo.cs

@@ -0,0 +1,3 @@
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("ConsoleApp.SourceGenerator.Tests")]

src/Sandbox/ConsoleApp.SourceGenerator/ConsoleAppSourceGenerator.cs

@@ -16,9 +16,11 @@ public class Payload
             public string? Version { get; set; }
         }
 
+        public string WarningMessage { get; set; }
+
         public ConsoleAppSourceGenerator() : base("ConsoleAppSourceGenerator")
         {
-
+            WarningMessage = "Warnigs show up in the 'Build' pane along with the 'Source Generators' pane";
         }
 
         public override void OnInitialize(SgfInitializationContext context)
@@ -29,7 +31,7 @@ public override void OnInitialize(SgfInitializationContext context)
                 Version = "13.0.1"
             };
 
-            Logger.Warning("Warnigs show up in the 'Build' pane along with the 'Source Generators' pane");
+            Logger.Warning(WarningMessage);
             Logger.Information("This is the output from the sournce generator assembly ConsoleApp.SourceGenerator");
             Logger.Information("This generator references Newtonsoft.Json and it can just be referenced without any other boilerplate");
             Logger.Information(JsonConvert.SerializeObject(payload));

src/SourceGenerator.Foundations.sln

@@ -31,6 +31,8 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Scripts", "Scripts", "{F012
 EndProject
 Project("{D954291E-2A0B-460D-934E-DC6B0785DB48}") = "SourceGenerator.Foundations.Shared", "SourceGenerator.Foundations.Shared\SourceGenerator.Foundations.Shared.shproj", "{8AF3630C-2BF5-4854-A45D-0074C2787964}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "ConsoleApp.SourceGenerator.Tests", "Sandbox\ConsoleApp.SourceGenerator.Tests\ConsoleApp.SourceGenerator.Tests.csproj", "{560C8028-2831-4697-9571-A9920FB972E7}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -87,6 +89,14 @@ Global
 		{E95587D6-78E8-48FE-9F98-371800A77B69}.Release|Any CPU.Build.0 = Release|Any CPU
 		{E95587D6-78E8-48FE-9F98-371800A77B69}.Release|x64.ActiveCfg = Release|Any CPU
 		{E95587D6-78E8-48FE-9F98-371800A77B69}.Release|x64.Build.0 = Release|Any CPU
+		{560C8028-2831-4697-9571-A9920FB972E7}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{560C8028-2831-4697-9571-A9920FB972E7}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{560C8028-2831-4697-9571-A9920FB972E7}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{560C8028-2831-4697-9571-A9920FB972E7}.Debug|x64.Build.0 = Debug|Any CPU
+		{560C8028-2831-4697-9571-A9920FB972E7}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{560C8028-2831-4697-9571-A9920FB972E7}.Release|Any CPU.Build.0 = Release|Any CPU
+		{560C8028-2831-4697-9571-A9920FB972E7}.Release|x64.ActiveCfg = Release|Any CPU
+		{560C8028-2831-4697-9571-A9920FB972E7}.Release|x64.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -95,6 +105,7 @@ Global
 		{DC8C5A1A-6269-4BA7-852A-D21CB0B2B5A0} = {A651676B-FBDB-4710-B010-D05AF3A56084}
 		{F4BA95B9-0353-44CA-9502-C74B532321B7} = {6118BF32-23BA-4D33-946E-F7E8A6F5D758}
 		{594AACB5-B550-46CF-B6E2-16EF826D655A} = {6118BF32-23BA-4D33-946E-F7E8A6F5D758}
+		{560C8028-2831-4697-9571-A9920FB972E7} = {6118BF32-23BA-4D33-946E-F7E8A6F5D758}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {EDB10920-970A-43F9-A2B3-7F1270DD477B}

src/SourceGenerator.Foundations/Templates/SourceGeneratorHostImpl.cs

@@ -24,36 +24,38 @@ namespace {{dataModel.Namespace}}
     internal class {{dataModel.ClassName}}Hoist : SourceGeneratorHoist, IIncrementalGenerator
     {
         // Has to be untyped otherwise it will try to resolve at startup
-        private object? m_generator;
+        private Lazy<object?> m_lazyGenerator;
 
+        /// <summary>
+        /// Creates a new generator host that will create an instance of {{dataModel.ClassName}} at runtime.
+        /// </summary>
         public {{dataModel.ClassName}}Hoist() : base()
         {
-            m_generator = null;        
+            m_lazyGenerator = new Lazy<object?>(CreateInstance);    
+        }
+
+        /// <summary>
+        /// Creates a new generator host that will reuse an existing instance of {{dataModel.ClassName}} instead of creating one dynamically.
+        /// This function would only ever be called from unit tests.
+        /// </summary>
+        public {{dataModel.ClassName}}Hoist({{dataModel.ClassName}} generator): base()
+        {
+            m_lazyGenerator = new Lazy<object?>(() => generator);    
         }
 
         /// <summary>
         /// Initializes the source generator to make it simpler to work with 
         /// </summary>
         public void Initialize(IncrementalGeneratorInitializationContext context)
         {
-            // The expected arguments types for the generator being created 
-            Type[] typeArguments = new Type[] { };
-
-            BindingFlags bindingFlags = BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance;
-            Type generatorType = typeof(global::{{dataModel.QualifedName}});
-            ConstructorInfo? constructor = generatorType.GetConstructor(bindingFlags, null, typeArguments, Array.Empty<ParameterModifier>());
+            IncrementalGenerator? generator = m_lazyGenerator.Value as IncrementalGenerator;
 
-            if(constructor == null)
+            if(generator == null)
             {
                 return;
             }
 
-
-            object[] constructorArguments = new  object[]{};
-            IncrementalGenerator generator = (global::{{dataModel.QualifedName}})constructor.Invoke(constructorArguments);
             ILogger logger = generator.Logger;
-
-            m_generator = generator;
             try
             {
                 SgfInitializationContext sgfContext = new(context, logger);
@@ -66,9 +68,29 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
             }
         }
 
+        private object? CreateInstance()
+        {
+            // The expected arguments types for the generator being created 
+            Type[] typeArguments = new Type[] { };
+
+            BindingFlags bindingFlags = BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance;
+            Type generatorType = typeof(global::{{dataModel.QualifedName}});
+            ConstructorInfo? constructor = generatorType.GetConstructor(bindingFlags, null, typeArguments, Array.Empty<ParameterModifier>());
+
+            if(constructor == null)
+            {
+                return null;
+            }
+
+            object[] constructorArguments = new  object[]{};
+            IncrementalGenerator generator = (global::{{dataModel.QualifedName}})constructor.Invoke(constructorArguments);
+
+            return generator;
+        }
+
         public void Dispose()
         {
-            if(m_generator is IDisposable disposable)
+            if(m_lazyGenerator.Value is IDisposable disposable)
             {
                 disposable.Dispose();
             }