Specify the return document type for AngularFirestoreDocument.get() #2361

The return type of the AngularFirestoreDocument.get() is not set, this will cause the editor cant perform autocomplete when calling DocumentSnapshot.data() because it will just treat its return type, as firestore.DocumentData instead the real type.

Version info

Angular: 9.0.7

Firebase: 7.11.0

AngularFire: 5.4.2

Other (e.g. Ionic/Cordova, Node, browser, operating system):
Node: v12.6
npm: 6.14.2
Browser: Latest chrome and firefox nightly.

How to reproduce these conditions

export class Sample {
  constructor(private afStore AngularFirestore) {}
  
  test(path: string)  {
    this.afStore.doc<SampleType>(path).get().pipe(take(1)).subscribe(doc => {
      console.log(doc.data()); // The real type of doc.data() is not infered by the editor.
    })
  }
}

Expected behavior

The return type should be

Observable<firebase.firestore.DocumentSnapshot<firebase.firestore.SamlpeType>>

This will allow to infer the type of the doc.data()

Actual behavior

The return type is

Observable<firebase.firestore.DocumentSnapshot<firebase.firestore.DocumentData>>

With this the autocomplete will not work

Possible Solution

Based on index.d.ts on firestore, it is implemented like this.

export class DocumentSnapshot<T = DocumentData> {
  data(options?: SnapshotOptions): T | undefined;
}

I think setting the return type of get on document.ts to

get(options?: firestore.GetOptions): Observable<firestore.DocumentSnapshot<T>>

will fix the issue.