param-pipe-bug.ts

/*
 * When using Graphql in NestJS, custom decorator invocations that include pipe 
 * constructors do not apply ultimately apply said pipes. Passing a pipe _instance_ 
 * works fine, hoever. The following test will fail because we expect that the output
 * would be "replacement" per `TestPipe.transform()` while instead it is "original", 
 * as if from a literal `@CustomParam()`.
 */

import { 
  createParamDecorator, 
  INestApplication, 
  Injectable, 
  Module, 
  PipeTransform 
} from '@nestjs/common';
import { GraphQLModule, Query, Resolver } from '@nestjs/graphql';
import { Test } from '@nestjs/testing';
import * as request from 'supertest';
import { Field, ObjectType } from 'type-graphql';


@Injectable()
class TestPipe implements PipeTransform {
  transform(_token: string): string {
    return 'replacement';
  }
}

@ObjectType()
class Result {

  @Field()
  public readonly text: string;

  constructor(text: string) {
    this.text = text;
  }
}

const CustomParam = createParamDecorator(() => 'original');

@Resolver(of => Result)
class TestResolver {
  @Query(returns => Result)
  result(@CustomParam(TestPipe) value: string): Result {
    return new Result({ text: value })
  }
}

@Module({
  providers: [{ provide: 'resolver', useClass: TestResolver }]
})
class TestModule {}

describe('ContextPipe', () => {
  let testHttpServer: request.SuperTest<request.Test>;
  let app: INestApplication;

  beforeAll(async () => {
    const mod = await Test.createTestingModule({
      imports: [
        TestModule,
        GraphQLModule.forRoot({
          debug: false,
          playground: false,
          autoSchemaFile: true,
          include: [TestModule],
          context: ({ req }) => ({ req }),
        }),
      ],
    }).compile();
    await mod.init();
    app = mod.createNestApplication();
    await app.init();
    testHttpServer = await request(app.getHttpServer());
  });

  afterAll(async () => {
    await app.close();
  });

  test('works with resolver', async (done) => {
    testHttpServer
        .post('/graphql')
        .send({
          operationName: null,
          variables: {},
          query: `{ result { text } }`
        })
        .expect(200, { data: { result: { text: 'replacement' } } })
        .end(done);
  });
});