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Add Module

.agents/skills/add-module/SKILL.md

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Add Module

High-ceremony. The part people get wrong is registration — a module must be wired in FOUR places (see Step 6). Architecture rules: .agents/rules/architecture.md.

Projects

src/Modules/{Name}/
├── Modules.{Name}/            ← runtime (internal): Domain/, Data/, Features/v1/, {Name}Module.cs
└── Modules.{Name}.Contracts/  ← public API: v1/ (commands/queries), Dtos/, Authorization/, Events/

Copy an existing module's two .csproj files (e.g. Modules.Catalog) and rename — don't hand-write project references. The runtime project references its Contracts project + the BuildingBlocks it needs; the Contracts project references Mediator + shared contracts.

Step 1 — [FshModule] is an ASSEMBLY attribute (not class-level)

In {Name}Module.cs, above the namespace:

csharp
[assembly: FshModule(typeof(FSH.Modules.{Name}.{Name}Module), 900)]   // (Type, order)

namespace FSH.Modules.{Name};

public sealed class {Name}Module : IModule
{
    public void ConfigureServices(IHostApplicationBuilder builder)
    {
        ArgumentNullException.ThrowIfNull(builder);
        PermissionConstants.Register({Name}Permissions.All);
        builder.Services.AddHeroDbContext<{Name}DbContext>();
        builder.Services.AddScoped<IDbInitializer, {Name}DbInitializer>();

        // Only if the module publishes/handles integration events:
        // builder.Services.AddEventingCore(builder.Configuration);
        // builder.Services.AddEventingForDbContext<{Name}DbContext>();
        // builder.Services.AddIntegrationEventHandlers(typeof({Name}Module).Assembly);

        builder.Services.AddHealthChecks()
            .AddDbContextCheck<{Name}DbContext>(name: "db:{name}");
    }

    public void ConfigureMiddleware(IApplicationBuilder app) { }   // optional, runs after auth

    public void MapEndpoints(IEndpointRouteBuilder endpoints)
    {
        ArgumentNullException.ThrowIfNull(endpoints);
        var versionSet = endpoints.NewApiVersionSet().HasApiVersion(new ApiVersion(1)).ReportApiVersions().Build();
        var group = endpoints.MapGroup("api/v{version:apiVersion}/{name}")
            .WithTags("{Name}").WithApiVersionSet(versionSet).RequireAuthorization();
        // group.MapCreate{Entity}Endpoint();  …
    }
}

Order controls load sequence (Auditing 300, Files 350, Webhooks 400, Billing 500, Catalog 600, Tickets 700, Notifications 750, Chat 800). If your module consumes another's events, load after it.

Step 2 — Permissions (Contracts/Authorization)

{Name}Permissions with nested resource classes and an All collection registered via PermissionConstants.Register({Name}Permissions.All). Mirror the shape of CatalogPermissions.

Step 3 — DbContext (extends BaseDbContext)

csharp
public sealed class {Name}DbContext : BaseDbContext
{
    public const string Schema = "{name}";

    public {Name}DbContext(
        IMultiTenantContextAccessor<AppTenantInfo> multiTenantContextAccessor,
        DbContextOptions<{Name}DbContext> options,
        IOptions<DatabaseOptions> settings,
        IHostEnvironment environment)
        : base(multiTenantContextAccessor, options, settings, environment) { }

    public DbSet<{Entity}> {Entities} => Set<{Entity}>();

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        ArgumentNullException.ThrowIfNull(modelBuilder);
        modelBuilder.HasDefaultSchema(Schema);
        modelBuilder.ApplyConfigurationsFromAssembly(typeof({Name}DbContext).Assembly);
        base.OnModelCreating(modelBuilder);   // MUST be last — applies tenant + soft-delete filters
    }
}

Step 4 — Solution + project references

bash
dotnet sln src/FSH.Starter.slnx add src/Modules/{Name}/Modules.{Name}/Modules.{Name}.csproj
dotnet sln src/FSH.Starter.slnx add src/Modules/{Name}/Modules.{Name}.Contracts/Modules.{Name}.Contracts.csproj

Add a <ProjectReference> to the runtime module from both FSH.Starter.Api and FSH.Starter.DbMigrator, and reference the runtime project from FSH.Starter.Migrations.PostgreSQL.

Step 5 — Migrations folder

Add a {Name}/ folder in src/Host/FSH.Starter.Migrations.PostgreSQL, then create the initial migration (see create-migration) with --context {Name}DbContext.

Step 6 — ⚠️ Register in ALL FOUR places (the footgun)

Identical edits in both FSH.Starter.Api/Program.cs and FSH.Starter.DbMigrator/Program.cs:

  1. Mediator o.Assemblies — add two markers: a Contracts type (e.g. typeof(FSH.Modules.{Name}.Contracts.{Name}ContractsMarker)) and the module type (typeof({Name}Module)).
  2. moduleAssemblies array — add typeof({Name}Module).Assembly.

Miss the Mediator marker → handlers silently undiscovered. Miss the assembly entry → module never loads. Miss the DbMigrator pair → migrate/seed skips the module.

Step 7 — Verify

bash
dotnet build src/FSH.Starter.slnx                  # 0 warnings
dotnet test src/Tests/Architecture.Tests           # boundary + tenant-isolation rules must pass
dotnet test src/FSH.Starter.slnx

Checklist

  • Two projects (copied csproj), added to .slnx, referenced from Api + DbMigrator (+ Migrations)
  • [assembly: FshModule(typeof({Name}Module), order)] (assembly-level, positional)
  • IModule: AddHeroDbContext<T>(), PermissionConstants.Register, version-set group, eventing trio if needed
  • {Name}DbContext : BaseDbContext, 4-arg ctor, base.OnModelCreating last
  • {Name}Permissions in Contracts/Authorization
  • Migrations folder + initial migration (--context {Name}DbContext)
  • Registered in all four places (Api + DbMigrator × Mediator + moduleAssemblies)
  • Build + Architecture.Tests green