DI doesn't inject a scoped request provider using @Inject and Symbol

[BrendonMFO]

Is there an existing issue for this?

• I have searched the existing issues

Current behavior

The DI isn't injecting/resolving a provider through @Inject when the property is a Symbol

This doesn't work:

@Injectable()
class TestTargetService {
  @Inject() // Scoped Request
  private readonly testService: TestService;

  @Inject(SYMBOL_INJECTOR) // Scoped Request
  private readonly [SYMBOL_SERVICE]: SymbolService;

  getTestService() {
    return this.testService;
  }

  getSymbolService() {
    return this[SYMBOL_SERVICE]; // undefined
  }
}

But injecting those same providers through the constructor, the DI resolves all providers perfectly

This does work:

@Injectable()
class TestTargetService {
  @Inject(SYMBOL_INJECTOR)
  private readonly [SYMBOL_SERVICE]: SymbolService;

  constructor(private readonly testService: TestService) {}

  getTestService() {
    return this.testService;
  }

  getSymbolService() {
    return this[SYMBOL_SERVICE]; // Symbol Service Instance
  }
}

I've spent a time debugging and found something about the cache of the metadatas. The property's instance wrapper was a new property but it was supposed to be an element inside the array, increasing its length. Was it supposed to be added as a new property?

Minimum reproduction code

https://github.com/BrendonMFO/nestjs-injection-bug

Steps to reproduce

1. npm i
2. npm test

There're two test files each one using a different way to inject the providers

Expected behavior

The DI should be able to resolve the dependencies through constructor and the decorator

Package

• I don't know. Or some 3rd-party package
• @nestjs/common
• @nestjs/core
• @nestjs/microservices
• @nestjs/platform-express
• @nestjs/platform-fastify
• @nestjs/platform-socket.io
• @nestjs/platform-ws
• @nestjs/testing
• @nestjs/websockets
• Other (see below)

Other package

No response

NestJS version

8.4.1

Packages versions

"dependencies": {
  "@nestjs/common": "^8.0.0",
  "@nestjs/core": "^8.0.0",
  "@nestjs/platform-express": "^8.0.0",
  "reflect-metadata": "^0.1.13",
  "rimraf": "^3.0.2",
  "rxjs": "^7.2.0"
}

Node.js version

16.13.1

In which operating systems have you tested?

• macOS
• Windows
• Linux

Other

No response

[micalevisk]

indeed. Here's a minimum reproduction of this: https://gitlab.com/micalevisk/nestjs-issue-9352

[micalevisk]

I was looking at the value on constructor. But this works (using the default scope):

const TokenSymbol = Symbol()
const A = Symbol('A')
const B = Symbol('B')

@Module({
  providers: [
    { provide: TokenSymbol, useValue: 'hello' },
    { provide: 'my-str-token', useValue: 'world' },
  ],
})
export class AppModule {
  @Inject(TokenSymbol) private readonly [A]: string
  @Inject('my-str-token') private readonly [B]: string

  onApplicationBootstrap() {
    console.table({ hello: this[A], world: this[B] })
  }
}
/*
┌─────────┬─────────┐
│ (index) │ Values  │
├─────────┼─────────┤
│  hello  │ 'hello' │
│  world  │ 'world' │
└─────────┴─────────┘
*/

Thus this should be a bug with the @Injectable({ scope: Scope.REQUEST }) + using symbol as a field name

[MyAeroCode]

I have fixed what was causing this issue.
I'll submit a PR as soon as I'm done writing the test code 😃

[kamilmysliwiec]

Let's track this here #9456