Vela - NestJS for the Edge

Vela lets you create custom parameter decorators to extract data from requests and metadata decorators to annotate handlers.

Parameter Decorators

Use createParamDecorator to define a custom parameter decorator. The factory function receives the decorator argument and the execution context:

import { createParamDecorator, ExecutionContext } from '@velajs/vela';

const CurrentUser = createParamDecorator(
  (data: string | undefined, ctx: ExecutionContext) => {
    const request = ctx.getRequest();
    const user = request.headers.get('x-user');
    return data ? user?.[data] : user;
  },
);

Use it in a controller:

@Controller('profile')
class ProfileController {
  @Get()
  getProfile(@CurrentUser() user: string) {
    return { user };
  }

  @Get('name')
  getName(@CurrentUser('name') name: string) {
    return { name };
  }
}

The returned decorator also accepts pipes as additional arguments, just like built-in parameter decorators:

@Get(':id')
findOne(@CurrentUser(undefined, RequiredPipe) user: string) {
  return { user };
}

Metadata Decorators

Use SetMetadata to attach custom metadata to handlers or controllers. This metadata can then be read by guards or interceptors using Reflector:

import { SetMetadata } from '@velajs/vela';

const Public = () => SetMetadata('isPublic', true);
const Roles = (...roles: string[]) => SetMetadata('roles', roles);

@Controller('spirits')
class SpiritsController {
  @Get()
  @Public()
  findAll() {
    return [];
  }

  @Post()
  @Roles('admin')
  create(@Body() body: { name: string }) {
    return body;
  }
}

Reading Metadata with Reflector

Inject Reflector to read metadata in guards or interceptors:

import { Injectable, CanActivate, ExecutionContext, Reflector } from '@velajs/vela';

@Injectable()
class AuthGuard implements CanActivate {
  constructor(private reflector: Reflector) {}

  canActivate(context: ExecutionContext) {
    const isPublic = this.reflector.get<boolean>('isPublic', context);
    if (isPublic) return true;

    const request = context.getRequest();
    return !!request.headers.get('authorization');
  }
}

Custom Decorators

Parameter Decorators

Metadata Decorators

Reading Metadata with Reflector

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