Classes with the same names are not injected properly

[stevenhair]

Bug Report

Current behavior

If you inject two classes with the same name, the first class in the providers list will be injected for both classes. This is a pretty rare issue, but many third-party packages export classes with generic names such as "Client".

A couple workarounds:

• Restructure your dependency tree so that you don't have both classes present in the same module (this may not be practical depending on your code)
• Extend the third-party class using a less generic name and use that throughout your code (this could lead to some bugs if you're not careful to always use your wrapper):

  import { Client } from 'foo';
  
  export class FooClient extends Client {}

• If you control one of the classes, simply rename it

Input Code

Here is a reproduction of this bug: https://github.com/stevenhair/congenial-palm-tree

Imagine that you have the module:

import { Client as FooClient } from 'foo';
import { Client as BarClient } from 'bar';

@Module({
  providers: [
    FooClient,
    BarClient,
    MyService,
  ]
})
export class MyModule {}

and a service:

import { Client as FooClient } from 'foo';
import { Client as BarClient } from 'bar';

export class MyService {
  constructor(
    private foo: FooClient,  // this will be an instance of FooClient
    private bar: BarClient,  // this will also be an instance of FooClient
  ) {}
}

Expected behavior

The correct class should be injected

Possible Solution

I suspect that somewhere along the line, the class name is being converted to a string. I'm not sure if this is in Nest.js code or the Typescript metadata. If it's in Nest.js code, hopefully it could be fixed by using a symbol or a more unique string. If it's due to the Typescript metadata, I'm not sure if this is solvable in Nest.

Environment

Nest version: 7.0.0

[jmcdo29]

Seems like a duplicate of this: #789

[stevenhair]

@jmcdo29 I believe that you are correct, it does appear to be a duplicate. I tried searching before opening the bug, but I guess that I didn't search hard enough.