Angular: Metadata collected contains an error that will be reported at runtime: Lambda not supported

问题

In my Angular app, I'm trying to use a factory provider in my module:

export function getMyFactory(): () => Window {
  return () => window;
}

@NgModule({
  providers: [
    { provide: WindowRef, useFactory: getMyFactory() },
  ],
})
export class MyModule {}

but this is failing with:

Error encountered in metadata generated for exported symbol 'MyModule':

Metadata collected contains an error that will be reported at runtime: Lambda not supported

回答1:

I've found an easy solution reported on a thread from GitHub: Arrow lambda not supported in static function posted by haochi

The solution is basically:

assigning the result to a variable, then return the variable

---

So in my case, I've resolved by replacing:

export function getMyFactory(): () => Window {
  return () => window;
}

with:

export function getMyFactory(): () => Window {
  const res = () => window;
  return res;
}

回答2:

I had the same issue trying to return a promise as a function, and replaced this:

export function myFunc(): Function {
    const result = () => ...
    return result;
}

With:

export function myFunc(){
    const result = () => ...
    return result;
}

来源：https://stackoverflow.com/questions/57594723/angular-metadata-collected-contains-an-error-that-will-be-reported-at-runtime