Adding new features to the Compiler Extension API

A compiler extension is a .NET assembly containing a public type implementing the IPackage interface in the Dassie.Extensions namespace. All features of the API are supported through special interfaces in this namespace. To add a new feature to the extension API, follow the below steps. The code below uses the IBuildLogWriter interface as an example.

Create a new public interface in the Dassie.Extensions namespace:

using System.IO;

namespace Dassie.Extensions;

/// <summary>
/// Defines a mechanism to write build logs using <see cref="System.IO.TextWriter"/>.
/// </summary>
public interface IBuildLogWriter
{
    /// <summary>
    /// The name of the log writer.
    /// </summary>
    public string Name { get; }

    /// <summary>
    /// The error severities at which the log writer is active.
    /// </summary>
    public BuildLogSeverity Severity { get; }

    /// <summary>
    /// All text writers making up the build log writer.
    /// </summary>
    public TextWriter[] Writers { get; }
}

Add a new virtual method to IPackage in order not to break existing implementations:

/// <summary>
/// An array of build log writers.
/// </summary>
public virtual IBuildLogWriter[] BuildLogWriters() => [];

Add a corresponding property to ExtensionLoader:

public static IEnumerable<IBuildLogWriter> BuildLogWriters => InstalledExtensions.Select(a => a.BuildLogWriters()).SelectMany(a => a);

Add a new section to the dc package info command output:

if (package.BuildLogWriters().Length != 0)
{
  sb.AppendLine();
  WriteHeading("Build log writers");

  foreach (IBuildLogWriter writer in package.BuildLogWriters())
    sb.AppendLine($"    {writer.Name}");
}

Modify relevant code parts of the compiler to support the new API feature.

Following these steps ensures the new API feature is correctly integrated and recognized by the compiler.

Table of Contents

Adding new features to the Compiler Extension API