Raiqub.Generators.InterpolationCodeWriter.CSharp 2.0.1

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Provides utility functions and helpers to aid in writing source files for source generators using high-performance writer and string interpolations

🏃 Quickstart   |   📗 Guide   |   📦 NuGet

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A high-performance source text writer for .NET incremental source generators. Write generated source code using plain strings or C# string interpolations with automatic indentation support.

NuGet Packages

• Raiqub.Generators.InterpolationCodeWriter: provides a compiled library with SourceTextWriter for writing source code
• Raiqub.Generators.InterpolationCodeWriter.CSharp: provides a compiled library with CodeWriterDispatcher and extensions for Roslyn source generators
• Raiqub.Generators.InterpolationCodeWriter.CSharp.Sources: provides source files that are embedded into your project (no runtime dependency)

Compatibility

The compiled libraries target .NET Standard 2.0, .NET 8, and .NET 10. The source files package requires at least the .NET 6.0 SDK, but you can target earlier frameworks.

Quickstart

Add the source files package to your source generator project:

dotnet add package Raiqub.Generators.InterpolationCodeWriter.CSharp.Sources

Then implement the ICodeWriter<T> interface to define your code writer:

public class MyWriter : ICodeWriter<MyModel>
{
    public bool CanGenerateFor(MyModel model) => model.Properties.Count > 0;

    public string GetFileName(MyModel model) => $"{model.Namespace ?? "_"}.{model.Name}Extensions.g.cs";

    public void Write(SourceTextWriter writer, MyModel model)
    {
        writer.WriteLine($"namespace {model.Namespace};");
        writer.WriteLine();
        writer.WriteLine($"public static partial class {model.Name}Extensions");
        writer.WriteLine("{");
        writer.PushIndent();

        // Write members using string interpolation...

        writer.PopIndent();
        writer.WriteLine("}");
    }
}

Guide

SourceTextWriter

SourceTextWriter is a high-performance text writer built on StringBuilder with automatic indentation support. It accepts plain strings and C# string interpolations through a custom InterpolatedStringHandler.

var writer = new SourceTextWriter();

writer.WriteLine("using System;");
writer.WriteLine();
writer.WriteLine($"namespace {ns};");
writer.WriteLine();
writer.WriteLine($"public class {className}");
writer.WriteLine("{");
writer.PushIndent();
writer.WriteLine($"public string Name {{ get; set; }}");
writer.PopIndent();
writer.WriteLine("}");

string result = writer.ToString();

Key features:

• Automatic indentation: Use PushIndent() / PopIndent() to manage indentation levels (4 spaces per level by default)
• String interpolation support: Write code using $"..." syntax directly
• Culture-invariant formatting: Numbers and other values are formatted using InvariantCulture by default
• Configurable: Customize line endings, indentation size, and format provider

ICodeWriter / ICodeWriter<T>

ICodeWriter defines a stateless code writer that generates source code. ICodeWriter<T> extends it with model-based generation:

• CanGenerateFor(T model) - determines if code should be generated for the given model
• GetFileName(T model) - returns the file name for the generated source
• Write(SourceTextWriter writer, T model) - writes the source code using the provided writer and model

Implementations should be stateless to ensure thread-safety in source generator contexts.

CodeWriterDispatcher

CodeWriterDispatcher<T> dispatches source generation across multiple code writers. It is stateless and safe to store as a static field:

private static readonly CodeWriterDispatcher<MyModel> s_dispatcher =
    new([new MyWriter1(), new MyWriter2()]);

Then call GenerateSources to generate source files using the SourceProductionContext:

private static void Emit(
    SourceProductionContext context,
    ImmutableArray<MyModel> types)
{
    s_dispatcher.GenerateSources(types, context);
}

An optional exception handler can be provided to report diagnostics instead of throwing:

private static readonly CodeWriterDispatcher<MyModel> s_dispatcher =
    new(
        (ex, model) => Diagnostic.Create(...),
        new MyWriter1(), new MyWriter2());

Contributing

If something is not working for you or if you think that the source file should change, feel free to create an issue or Pull Request. I will be happy to discuss and potentially integrate your ideas!

License

See the LICENSE file for details.