NestJS - Add additional metadata to Pipes

Question

Is there a way to add additional metadata to a NestJS pipe?

The metadata property has these values:

export interface ArgumentMetadata {
  type: 'body' | 'query' | 'param' | 'custom';
  metatype?: Type<any>;
  data?: string;
}

See: https://docs.nestjs.com/pipes

Answer 1

I was able to add additional metadata via a custom parameter decorator, and a custom pipe.

import { createParamDecorator} from '@nestjs/common'

export const ExtractIdFromBody = createParamDecorator(
  (
    {
      property,
      entityLookupProperty = 'id'
    }: {
      property: string
      entityLookupProperty?: string
    },
    req
  ) => {
    const value = get(req.body, property)
    return {
      value,
      entityLookupProperty // the extra property
    }
  }
)

Then I used a the decorator like this:

@Post()
@UsePipes(new ValidationPipe({ transform: true }))
async doThing(
    @ExtractIdFromBody({ property: 'userId', entityLookupProperty: 'someProperty'  }, GetEntityOr404Pipe) entity: Entity,
  ): Promise<Entity[]> {
    return await this.Service.doThing(entity)
  }