Verify.SourceGenerators

Extends Verify to allow verification of C# Source Generators.

See Milestones for release notes.

NuGet package

https://nuget.org/packages/Verify.SourceGenerators/

Install one of the Verify testing framework adapters NuGet packages.

Initialize

[ModuleInitializer]
public static void Init() =>
    VerifySourceGenerators.Initialize();

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Generator

Given a Source Generator:

using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.Text;

[Generator]
public class HelloWorldGenerator :
    ISourceGenerator
{
    public void Execute(GeneratorExecutionContext context)
    {
        var source1 = """
                      using System;
                      public static class Helper
                      {
                          public static void Method()
                          {
                          }
                      }
                      """;
        context.AddSource("helper", SourceText.From(source1, Encoding.UTF8));

        var source2 = """
                      using System;
                      public static class HelloWorld
                      {
                          public static void SayHello()
                          {
                              Console.WriteLine("Hello from generated code!");
                          }
                      }
                      """;
        var sourceText = SourceText.From(source2, Encoding.UTF8);
        context.AddSource("helloWorld", sourceText);

        var descriptor = new DiagnosticDescriptor(
            id: "theId",
            title: "the title",
            messageFormat: "the message from {0}",
            category: "the category",
            DiagnosticSeverity.Info,
            isEnabledByDefault: true);

        var location = Location.Create(
            Path.Combine("dir", "theFile.cs"),
            new(1, 2),
            new(
                new(1, 2),
                new(3, 4)));
        var diagnostic = Diagnostic.Create(descriptor, location, "hello world generator");
        context.ReportDiagnostic(diagnostic);
    }

    public void Initialize(GeneratorInitializationContext context)
    {
    }
}

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Test

Can be tested as follows:

This snippets assumes use of the XUnit Verify adapter, change the using VerifyXUnit if using other testing frameworks.

public class SampleTest
{
    [Fact]
    public Task Driver()
    {
        var driver = BuildDriver();

        return Verify(driver);
    }

    [Fact]
    public Task RunResults()
    {
        var driver = BuildDriver();

        var results = driver.GetRunResult();
        return Verify(results);
    }

    [Fact]
    public Task RunResult()
    {
        var driver = BuildDriver();

        var result = driver.GetRunResult().Results.Single();
        return Verify(result);
    }

    static GeneratorDriver BuildDriver()
    {
        var compilation = CSharpCompilation.Create("name");
        var generator = new HelloWorldGenerator();

        var driver = CSharpGeneratorDriver.Create(generator);
        return driver.RunGenerators(compilation);
    }
}

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Results

And will result in the following verified files:

Info file

An info file containing all metadata about the current state. eg any Diagnostics.

{
  Diagnostics: [
    {
      Location: dir\theFile.cs: (1,2)-(3,4),
      Message: the message from hello world generator,
      Severity: Info,
      WarningLevel: 1,
      Descriptor: {
        Id: theId,
        Title: the title,
        MessageFormat: the message from {0},
        Category: the category,
        DefaultSeverity: Info,
        IsEnabledByDefault: true
      }
    }
  ]
}

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Source Files

Multiple source files. One for each GeneratorDriverRunResult.Results.GeneratedSources.

//HintName: helloWorld.cs
using System;
public static class HelloWorld
{
    public static void SayHello()
    {
        Console.WriteLine("Hello from generated code!");
    }
}

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Manipulating Source

To manipulating the source of the generated cs files, use Scrubbers.

For example to remove all lines start with using:

[Fact]
public Task ScrubLines()
{
    var driver = GeneratorDriver();

    return Verify(driver)
        .ScrubLines(_ => _.StartsWith("using "));
}

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Ignoring Files

To ignore specific source text use IgnoreGeneratedResult. This uses an expression of type Func<GeneratedSourceResult, bool> to determine which outputs are ignored.

For example to ignore files with the name helper or that contain the text static void SayHello():

[Fact]
public Task IgnoreFile()
{
    var driver = GeneratorDriver();

    return Verify(driver)
        .IgnoreGeneratedResult(
            _ => _.HintName.Contains("helper") ||
                 _.SourceText
                     .ToString()
                     .Contains("static void SayHello()"));
}

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Notes:

• Source Generators Cookbook / Testing

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Sauce designed by April Hsuan from The Noun Project.