IIncrementalGenerator How To: Unit Tests add Additional File?

[FrankKubis]

I try to add a File with BuildAction "AdditonalFile" to the UnitTest of my IIncrementalGenerator. I did follow the cookbock.

Relevant parts of my IncrementalGenerator:

public class ApplicationModelIncrementalSourceGenerator : IIncrementalGenerator
{
    private const string ModelFileName = @"Model.yaml";

    public void Initialize(IncrementalGeneratorInitializationContext context)
    {
        // Model file has to be marked as "AdditionalFile" in build action
        var provider = context.AdditionalTextsProvider
            // Find the model file
            .Where(x => x.Path.EndsWith(ModelFileName))
            // Convert the reference into AdditionalFile Type that we use below
            .Select((x, cancellationToken) =>
            {
                var path       = x.Path;
                var sourceText = x.GetText(cancellationToken);
                if (string.IsNullOrEmpty(path) || sourceText is null)
                {
                    return null;
                }

                return new AdditionalFile(path, sourceText.ToString());
            });

        // Runs for each change of model
        context.RegisterSourceOutput(provider, Execute);
        
    }

    private static void Execute(SourceProductionContext context, AdditionalFile? modelFile)
    {
    }
}

I tried to add the file as additional text using this.

        driver.AddAdditionalTexts([
            new InMemoryAdditionalText(@"c:\src\Model.yaml", @"
Alias: ExampleApplication")]);

This seems not working, how to add a file for testing?

The complete test fact:

    [Fact]
    public void ExpectedFilesGetGenerated()
    {
        var inputCompilation = CreateCompilation(@"
namespace UnitTest.Generated
{
    public class Program
    {
        public static void Main(string[] args)
        {
        }
    }
}
");

        // // Create an instance of the source generator.
        var generator = new ApplicationModelIncrementalSourceGenerator();
        //
        // Create the driver that will control the generation, passing in our generator
        var driver = CSharpGeneratorDriver.Create(generator.AsSourceGenerator());

        driver.AddAdditionalTexts([
            new InMemoryAdditionalText(@"c:\src\Model.yaml", @"
Alias: ExampleApplication")]);

        // Run the generation pass
        // (Note: the generator driver itself is immutable, and all calls return an updated version of the driver that you should use for subsequent calls)
        var generatorDriver = driver.RunGeneratorsAndUpdateCompilation(inputCompilation, out var outputCompilation, out var diagnostics);
        var runResult       = generatorDriver.GetRunResult();
        var generatorResult = runResult.Results.FirstOrDefault();

        diagnostics.IsEmpty.Should().BeTrue();
        outputCompilation.GetDiagnostics().Should().BeEmpty();
        generatorResult.Exception.Should().BeNull();
        generatorResult.GeneratedSources.Length.Should().Be(6);
    }

    private static Compilation CreateCompilation(string source)
    {
        var assemblyLocation = typeof(Binder).GetTypeInfo().Assembly.Location;
        return CSharpCompilation.Create("compilation",
            [CSharpSyntaxTree.ParseText(source)],
            [MetadataReference.CreateFromFile(assemblyLocation)],
            new CSharpCompilationOptions(OutputKind.ConsoleApplication));
    }

The helper class

internal class InMemoryAdditionalText(string path, string content) : AdditionalText
{
    private readonly SourceText _content = SourceText.From(content, Encoding.UTF8);

    public override string Path { get; } = path;

    public override SourceText GetText(CancellationToken cancellationToken = default)
        => _content;
}

[333fred]

You're not saving the results of the Add call. Practically every public api in Roslyn is immutable; if you're not saving the result somewhere, it's a good indicator that you've done something wrong.