Classes exported under the same name and aliased are confused as the same token by the dependency injection mechanism

Bug Report

Input Code

Consider the following minimal project:

// provider1.ts
export class Token {};

// provider2.ts
export class Token {};

// main.module.ts
import {Module} from "@nestjs/common";
import {Token as Token1} from "./provider1";
import {Token as Token2} from "./provider2";

@Module({
    providers: [
        Token1,
        Token2,
        {
            provide: 'foo',
            useFactory: (injectedToken1, injectedToken2) => {
                console.warn(Token1 === Token2); // false, expected
                console.warn(injectedToken1 === injectedToken2); // true, unexpected
                console.warn(injectedToken1 instanceof Token2); // true, unexpected
                console.warn(injectedToken2 instanceof Token2); // true, expected
            },
            inject: [
                Token1,
                Token2
            ]
        }
    ]

})
export class MainModule {}

Here, provider1.ts and provider2.ts both export a class under the same name - Token. When imported by the module, they are aliased respectively to Token1 and Token2. These aliases are then used as provider keys.

When both tokens are injected into the foo provider factory, both arguments of the factory are strictly equals: they are both the same instance of Token2. It means that the dependency injection mechanism instanciate a singleton from Token2 and then assign this singleton to both the tokens Token1 and Token2.

Expected behavior

Token1 and Token2 are different classes. They are different tokens and are not equal, nor loosely, neither strictly.

It is expected that they are not confused by the dependency injection mechanism of Nest.

Possible Solution

None.

And this is a big issue because there is no way for a developer to control how a class is exported by a module the application depends on. When two different modules export the same class, it becomes impossible to alias them and use these aliases as provider keys.

Note that this also impacts functions used as factory.

Environment

Nest version: 7.6.17

[kamilmysliwiec]

This has been fixed in v8 https://github.com/nestjs/nest/pull/6349 (which I’m hoping to release within ~1 month).

[ericmorand]

@kamilmysliwiec

core: use class references as providers/controllers/injectables keys instead of their names

👍

Amazing, thanks a lot!