Module Auto-Discovery

The Module Auto-Discovery generator scans all referenced assemblies for IModuleRegistration implementations and produces AddAllModules() and MapAllModuleEndpoints() extension methods. This eliminates the need for a manually maintained ModuleRegistration.cs file in the host project.

What It Replaces

Previously, adding a module required updating the host's composition root:

// Old approach -- manual ModuleRegistration.cs
public static class ModuleRegistration
{
    public static IServiceCollection AddModules(
        IServiceCollection services, IConfiguration configuration)
    {
        CatalogModule.ConfigureServices(services, configuration);
        OrderingModule.ConfigureServices(services, configuration);
        // Must manually add each new module here
        return services;
    }

    public static WebApplication MapModuleEndpoints(this WebApplication app)
    {
        CatalogModule.ConfigureEndpoints(app);
        OrderingModule.ConfigureEndpoints(app);
        // Must manually add each new module here
        return app;
    }
}

The source generator replaces this entirely:

// New approach -- source-generated
builder.Services.AddAllModules(builder.Configuration);
app.MapAllModuleEndpoints();

How It Works

1. The generator runs in the host project (e.g., EShop.WebApi)
2. It scans all referenced assembly symbols for types implementing IModuleRegistration
3. It verifies each type has both static methods: ConfigureServices() and ConfigureEndpoints()
4. It generates a GeneratedModuleRegistration class that calls each module in order

What Gets Generated

public static class GeneratedModuleRegistration
{
    public static IServiceCollection AddAllModules(
        this IServiceCollection services, IConfiguration configuration)
    {
        CatalogModule.ConfigureServices(services, configuration);
        OrderingModule.ConfigureServices(services, configuration);
        return services;
    }

    public static IEndpointRouteBuilder MapAllModuleEndpoints(
        this IEndpointRouteBuilder app)
    {
        CatalogModule.ConfigureEndpoints(app);
        OrderingModule.ConfigureEndpoints(app);
        return app;
    }
}

Module Ordering

By default, modules are registered in alphabetical order by fully qualified type name. Control the order with the [ModuleOrder] attribute:

using Modulus.Mediator.Abstractions;

[ModuleOrder(1)]
public class CatalogModule : IModuleRegistration
{
    public static IServiceCollection ConfigureServices(
        IServiceCollection services, IConfiguration configuration) { /* ... */ }

    public static IEndpointRouteBuilder ConfigureEndpoints(
        IEndpointRouteBuilder app) { /* ... */ }
}

[ModuleOrder(2)]
public class OrderingModule : IModuleRegistration
{
    public static IServiceCollection ConfigureServices(
        IServiceCollection services, IConfiguration configuration) { /* ... */ }

    public static IEndpointRouteBuilder ConfigureEndpoints(
        IEndpointRouteBuilder app) { /* ... */ }
}

Lower values execute first. Modules with equal order values are sorted alphabetically.

Usage in Program.cs

var builder = WebApplication.CreateBuilder(args);

// Register all module services (source-generated)
builder.Services.AddAllModules(builder.Configuration);

var app = builder.Build();

// Map all module endpoints (source-generated)
app.MapAllModuleEndpoints();

app.Run();

Impact on CLI

The modulus add-module command is simplified by this generator:

• Before: The CLI had to modify ModuleRegistration.cs to add the new module's registration calls
• After: The CLI only needs to create the module projects and add them to the solution. The generator picks up the new IModuleRegistration implementation automatically on the next build

Generator Diagnostic

ID	Severity	Message
MODGEN004	Warning	IModuleRegistration implementation is missing ConfigureServices() or ConfigureEndpoints()

If a type implements IModuleRegistration but is missing one of the required static methods, the generator emits a warning and skips that module from auto-registration.

See Also

• Handler Registration -- Auto-register handlers within each module
• Architecture Overview -- How modules compose into the host
• CLI: add-module -- Adding modules to your solution