klod68/gen-middleware

name: gen-middleware description: "Use when adding custom middleware to an ASP.NET Core pipeline. Generates a middleware class for a single cross-cutting concern (e.g., request logging, correlation ID, tenant resolution) and an IApplicationBuilder extension method. Also invoke when the user mentions: custom middleware, pipeline middleware, request middleware, ASP.NET middleware class. Domain: Code Generation, Infrastructure. Level: Intermediate."

Generate an ASP.NET Core middleware for the ${1:ConcernName} concern.

Context

• Namespace root: ${2:MyApp}
• Concern description: ${3:Brief description of what the middleware should do}
• Pipeline position: ${4:Before or after which existing middleware}

Required output — generate ALL of the following:

1. Middleware class

${2}.Middleware.${1}Middleware.cs

/// <summary>
/// Middleware that handles ${1:concern} for all HTTP requests.
/// </summary>
public sealed class ${1}Middleware
{
    private readonly RequestDelegate _next;
    private readonly ILogger<${1}Middleware> _logger;

    public ${1}Middleware(RequestDelegate next, ILogger<${1}Middleware> logger)
    {
        ArgumentNullException.ThrowIfNull(next);
        ArgumentNullException.ThrowIfNull(logger);
        _next = next;
        _logger = logger;
    }

    public async Task InvokeAsync(HttpContext context)
    {
        // PRE-processing (before next middleware)
        // ...

        await _next(context);

        // POST-processing (after next middleware)
        // ...
    }
}

2. Extension method

${2}.Middleware.${1}MiddlewareExtensions.cs

/// <summary>
/// Registers the <see cref="${1}Middleware"/> in the application pipeline.
/// </summary>
public static class ${1}MiddlewareExtensions
{
    public static IApplicationBuilder Use${1}(this IApplicationBuilder builder)
    {
        ArgumentNullException.ThrowIfNull(builder);
        return builder.UseMiddleware<${1}Middleware>();
    }
}

3. Options class (if configurable)

${2}.Configuration.${1}Options.cs

• Only generate if the middleware has configurable behavior
• Follow the Options Pattern with EnsureValid() method
• Register in DI with Configure<${1}Options>

Rules

• Middleware class is public sealed — one concern per middleware
• Constructor takes RequestDelegate next as first parameter, then DI services
• Method is InvokeAsync (not Invoke) — always async
• Guard clauses on constructor parameters
• Extension method is Use${1} on IApplicationBuilder
• Never catch exceptions unless this IS the exception handling middleware
• Use ILogger<T> for logging — never Console.WriteLine
• Request-scoped services are resolved via HttpContext.RequestServices (not constructor)
• XML doc on the class and extension method

Constraints

• Follow all rules in the workspace root instruction file
• Single responsibility — one cross-cutting concern per middleware
• Middleware should be stateless (any state goes in HttpContext.Items or options)
• Do not duplicate functionality already in ASP.NET Core built-in middleware