Documention Update: Pipes with config AND dependency

Bug Report

Current behavior

Your docs give great examples of how to configure a Pipe for DI or an options object but not both. The use case below would allow me to create one pipe that I could configure for any request object by supplying the property name containing the file path value. As it stands, I would basically need to create the same pipe over and over again for requests with different request signatures. This example is contrived but hopefully you could see how it could be beneficial.

Input Code

pipe.ts

@Injectable()
export class FileExistsPipe implements PipeTransform {

  constructor(private filePath: string, db: DatabaseService) { }

  async transform(value: any, metadata: ArgumentMetadata) {
    const path = value[this.filePath];
    const doesExist =  await this.db.file(path).exists()
    if(!doesExist)  throw new BadRequestException();
    return value;
  }
}

controller.ts

interface JobRequest {
   input: 'path/to/file/on/server'
}

@Controller('transcode')
export class TranscodeController {

  @Post()
  async transcode ( 
    @Body( new FileExistsPipe('input')) transcodeRequest: JobRequest) {
    return await this.videoProducer.addJob(transcodeRequest);
  }

Expected behavior

The above solution doesn’t work because the call to new FileExistsPipe('input') needs two arguments, the second being the DatabaseService dependency. The other option would be to do @Body(FileExistsPipe) but then I wouldn’t be able to pass my property name to my pipe to look up in the request object.

Possible Solution

I have posted this question on stackoverflow, here, in case you would prefer to leave the documentation as is.

[nartc]

@tommyc38 I just checked your repo (sorry for missing it before). Your DatabaseService is undefined in the FIleExistPipe because you use the pipe in AppController. AppController will be resolved before the DatabaseModule gets resolved. You can use forwardRef() to inject the DatabaseService in your pipe if you are going to use the pipe in AppController. The good practice here is to have feature controllers provided in feature modules.

export const FileExistPipe: (filePath: string) => PipeTransform = memoize(
  createFileExistPipe
);

function createFileExistPipe(filePath: string): Type<PipeTransform> {
  class MixinFileExistPipe implements PipeTransform {
    constructor(
      // use forwardRef here
      @Inject(forwardRef(() => DatabaseService)) private db: DatabaseService 
    ) {
      console.log(db);
    }

    async transform(value: ITranscodeRequest, metadata: ArgumentMetadata) {
      console.log(filePath, this.db);
      const doesExist = await this.db.checkFileExists(filePath);
      if (!doesExist) throw new BadRequestException();
      return value;
    }
  }

  return mixin(MixinFileExistPipe);
}

this is the fix btw

[tommyc38]

https://github.com/tommyc38/nest-pipe-repro

@nartc , I included instructions in the README. Should be pretty straightforward. Note, I am also creating another Nest repro and am using this for that as well.