Error and Context Merging

Handler context is calculated from active pre-handlers.

NOTE

In this example, AuthMiddleware and TenantMiddleware are assumed to be registered globally via a global module (globalModules in DIContext.create(...)).

• With AuthMiddleware + TenantMiddleware, handler context includes both userId and tenantId.
• If middlewares return Result, their error types are merged into handler returnType.

import { type Handler, type QueryContract, Result } from "awilixify";
import type { UsersModuleDef } from "./users.module";

class HandlerError extends Error {}
type Response = Result<{ id: string }, HandlerError>;

export class GetUserHandler implements Handler<GetUserHandler["contract"]> {
  static readonly key = "users/get";
  declare readonly contract: QueryContract<
    typeof GetUserHandler.key,
    { userId: string },
    Response
  >;

  async executor(
    payload: this["contract"]["payload"],
    // { userId: string; tenantId: string }
    context: this["contract"]["context"],
  ) {
    return Result.ok({ id: payload.userId });
  }
}

From the execute side, merged errors are also inferred!

// result: Result<{ id: string }, HandlerError | UnauthorizedError | TenantNotFoundError>
const result = await this.queryMediator.execute("users/get", {
  userId: req.params.id,
});

NOTE

If at least one active pre-handler returns Result, contract returnType is merged into Result<Success, HandlerError | MiddlewareErrors>. If no pre-handler returns Result, the plain handler response type is preserved.