Framework for unit testing generators

GeneratorTests.cs

using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using System.Collections.Immutable;
using System.Linq;
using System.Reflection;
using Xunit;

namespace GeneratorTests.Tests
{
    public class GeneratorTests
    {
        [Fact]
        public void SimpleGeneratorTest()
        {
            string userSource = @"
namespace MyCode
{
    public class Program
    {
        public static void Main(string[] args)
        {
        }
    }
}
";
            Compilation comp = CreateCompilation(userSource);
            var newComp = RunGenerators(comp, out var generatorDiags, new SimpleGenerator());

            Assert.Empty(generatorDiags);
            Assert.Empty(newComp.GetDiagnostics());
        }



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

        private static GeneratorDriver CreateDriver(Compilation c, params ISourceGenerator[] generators)
            => new CSharpGeneratorDriver(c.SyntaxTrees.First().Options,
                ImmutableArray.Create(generators),
                null,
                ImmutableArray<AdditionalText>.Empty);

        private static Compilation RunGenerators(Compilation c, out ImmutableArray<Diagnostic> diagnostics, params ISourceGenerator[] generators)
        {
            CreateDriver(c, generators).RunGeneratorsAndUpdateCompilation(c, out var d, out diagnostics);
            return d;
        }
    }
}

Note that due to an API change the CreateDriver method needs to change to:

        private static GeneratorDriver CreateDriver(Compilation c, params ISourceGenerator[] generators)
            => new CSharpGeneratorDriver(c.SyntaxTrees.First().Options,
                ImmutableArray.Create(generators),
                null,
                ImmutableArray<AdditionalText>.Empty);

Updated, thanks @davidwengier

Hi @chsienki

GeneratorDriver.RunFullGeneration is now obsolete. It needs to be updated with RunGeneratorsAndUpdateCompilation.

CSharpGeneratorDriver constructor is also obsolete. It needs to be updated with CSharpGeneratorDriver.Create.

Also, ParseOptions will need a cast to CSharpParseOptions.

Is anyone is interested here is a version that works for me (with all the notes above):

private static Compilation CreateCompilation(string source) => CSharpCompilation.Create(
    assemblyName: "compilation",
    syntaxTrees: new[] { CSharpSyntaxTree.ParseText(source, new CSharpParseOptions(LanguageVersion.Preview)) },
    references: new[] { MetadataReference.CreateFromFile(typeof(Binder).GetTypeInfo().Assembly.Location) },
    options: new CSharpCompilationOptions(OutputKind.ConsoleApplication)
);

private static GeneratorDriver CreateDriver(Compilation compilation, params ISourceGenerator[] generators) => CSharpGeneratorDriver.Create(
    generators: ImmutableArray.Create(generators),
    additionalTexts: ImmutableArray<AdditionalText>.Empty,
    parseOptions: (CSharpParseOptions)compilation.SyntaxTrees.First().Options,
    optionsProvider: null
);

private static Compilation RunGenerators(Compilation compilation, out ImmutableArray<Diagnostic> diagnostics, params ISourceGenerator[] generators)
{
    CreateDriver(compilation, generators).RunGeneratorsAndUpdateCompilation(compilation, out var updatedCompilation, out diagnostics);
    return updatedCompilation;
}

Would it be possible to pass AnalyzerConfigOptions using this model? I have a generator that depends on a project property being set, and to test it I am having to comment out the property check in the generator.

Would it be possible to pass AnalyzerConfigOptions using this model? I have a generator that depends on a project property being set, and to test it I am having to comment out the property check in the generator.

@sharwell Does the testing library supports passing .editorconfig for generators? (it does for analyzers & codefixes, but not sure about generators)

@sharwell Does the testing library supports passing .editorconfig for generators? (it does for analyzers & codefixes, but not sure about generators)

Yes, you can add them to TestState.AnalyzerConfigFiles.