Tighter parameter decorator checking with --experimentalDecorators

// @experimentalDecorators: true
export declare const Inject:
  (entity: Function, dataSource?: string) =>
    (target: object, key: string | symbol, index?: number) => void;

export class Foo {}

export class C {
  constructor(@Inject(Foo) x: any) {  }
}

Previously: no error
In main/5.0:

Unable to resolve signature of parameter decorator when called as an expression.
  Argument of type 'undefined' is not assignable to parameter of type 'string | symbol'

Was this...possibly always a bug with --experimentalDecorators?

Yes, it seems this was a bug in type-checking parameter decorators on constructors under --experimentalDecorators with TypeScript 4.9 and prior.

In #50820, we fixed up the way we type-checked decorators. This catches some issues, like decorators which expect a defined key; however, parameter decorators in constructors don't get passed a key. As a result, libraries with dependency injection decorator functions like inversify (pre-6.0), NestJS, and others (often named inject, Inject, and InjectRepository) might need to be corrected to accept an undefined key (or to have an overload which accepts an undefined key).

inversify's @inject works fine starting in [email protected]. @nestjs/common's @inject needs to be updated, however.

Is tsyringe affected?

Yes, I believe so.

I filed an issue at NestJS over at #52435. I'm not sure how active TSyringe is at the moment.

This issue has been marked 'Working as Intended' and has seen no recent activity. It has been automatically closed for house-keeping purposes.

I was able to solve this problem by adding these parameters to the tsconfig.json file:

I used inversify: 6.0.1 version

NOTE: when I inserted it at the end of the file it didn't work, only when I put it at the beginning

{
  "compilerOptions": {
      "emitDecoratorMetadata": true,
      "experimentalDecorators": true,
      "allowJs": true,
  }
}

I hope I can help 😄

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Tighter parameter decorator checking with `--experimentalDecorators` #52435

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Tighter parameter decorator checking with --experimentalDecorators #52435

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DanielRosenwasser commented on Jan 26, 2023

DanielRosenwasser commented on Jan 26, 2023

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Evaldoes commented on Jan 7, 2024

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Tighter parameter decorator checking with `--experimentalDecorators` #52435