Middleware

Cross-cutting logic - auth checks, logging, timing - lives in middleware and stays out of handler methods.

Implement ICommandMiddleware:

public class TimingMiddleware : ICommandMiddleware
{
    public async Task InvokeAsync(CommandContext ctx, Func<Task> next)
    {
        var sw = Stopwatch.StartNew();
        await next();
        Console.Error.WriteLine($"{ctx.CommandPath}: {sw.ElapsedMilliseconds}ms");
    }
}
		

Runs for every command:

app.UseMiddleware<TimingMiddleware>();
		

Apply via attribute on the method:

[MiddlewareAttribute<TimingMiddleware>]
public static Task<int> Deploy(string environment) { … }
		

ICommandMiddleware receives CommandContext with:

• CommandPath - the matched command path
• Args - the raw arguments
• ExitCode - settable exit code
• CancellationToken - the cancellation token for the invocation

The pipeline is wired in generated code, not a runtime delegate chain. Each middleware call is emitted as a direct invocation in the generated dispatch method. There is no runtime list to build or iterate.

When using Nullean.Argh.Hosting, middleware types are resolved from the DI container. Control lifetimes with the overload:

builder.Services.AddArgh(args, b =>
{
    b.UseMiddleware<AuditMiddleware>(ServiceLifetime.Singleton);
});