[types] Get flow type working again; Fix majority of firestore type issues

lib/modules/firestore/DocumentReference.js

@@ -3,11 +3,13 @@
  * DocumentReference representation wrapper
  */
 import CollectionReference from './CollectionReference';
-import DocumentSnapshot from './DocumentSnapshot';
-import Path from './Path';
+import DocumentSnapshot, { type DocumentSnapshotNativeData } from './DocumentSnapshot';
 import { buildNativeMap } from './utils/serialize';
 import { firestoreAutoId, isFunction, isObject, isString } from '../../utils';
 
+import type Firestore from './';
+import type Path from './Path';
+
 export type WriteOptions = {
   merge?: boolean,
 }
@@ -16,24 +18,27 @@ type DocumentListenOptions = {
   includeMetadataChanges: boolean,
 }
 
+type ObserverOnError = (Object) => void;
+type ObserverOnNext = (DocumentSnapshot) => void;
+
 type Observer = {
-  next: (DocumentSnapshot) => void,
-  error?: (Object) => void,
+  error?: ObserverOnError,
+  next: ObserverOnNext,
 }
 
- /**
+/**
  * @class DocumentReference
  */
 export default class DocumentReference {
   _documentPath: Path;
-  _firestore: Object;
+  _firestore: Firestore;
 
-  constructor(firestore: Object, documentPath: Path) {
+  constructor(firestore: Firestore, documentPath: Path) {
     this._documentPath = documentPath;
     this._firestore = firestore;
   }
 
-  get firestore(): Object {
+  get firestore(): Firestore {
     return this._firestore;
   }
 
@@ -43,6 +48,9 @@ export default class DocumentReference {
 
   get parent(): CollectionReference {
     const parentPath = this._documentPath.parent();
+    if (!parentPath) {
+      throw new Error('Invalid document path');
+    }
     return new CollectionReference(this._firestore, parentPath);
   }
 
@@ -71,9 +79,9 @@ export default class DocumentReference {
   }
 
   onSnapshot(
-    optionsOrObserverOrOnNext: DocumentListenOptions | Observer | (DocumentSnapshot) => void,
-    observerOrOnNextOrOnError?: Observer | (DocumentSnapshot) => void | (Object) => void,
-    onError?: (Object) => void
+    optionsOrObserverOrOnNext: DocumentListenOptions | Observer | ObserverOnNext,
+    observerOrOnNextOrOnError?: Observer | ObserverOnNext | ObserverOnError,
+    onError?: ObserverOnError,
   ) {
     let observer = {};
     let docListenOptions = {};
@@ -125,8 +133,8 @@ export default class DocumentReference {
     }
     const listenerId = firestoreAutoId();
 
-    const listener = (nativeDocumentSnapshot) => {
-      const documentSnapshot = new DocumentSnapshot(this, nativeDocumentSnapshot);
+    const listener = (nativeDocumentSnapshot: DocumentSnapshotNativeData) => {
+      const documentSnapshot = new DocumentSnapshot(this.firestore, nativeDocumentSnapshot);
       observer.next(documentSnapshot);
     };
 
@@ -158,7 +166,7 @@ export default class DocumentReference {
       .documentSet(this.path, nativeData, writeOptions);
   }
 
-  update(...args: Object | string[]): Promise<void> {
+  update(...args: Array<any>): Promise<void> {
     let data = {};
     if (args.length === 1) {
       if (!isObject(args[0])) {
@@ -190,7 +198,7 @@ export default class DocumentReference {
    * Remove document snapshot listener
    * @param listener
    */
-  _offDocumentSnapshot(listenerId: number, listener: Function) {
+  _offDocumentSnapshot(listenerId: string, listener: Function) {
     this._firestore.log.info('Removing onDocumentSnapshot listener');
     this._firestore.removeListener(this._firestore._getAppEventName(`onDocumentSnapshot:${listenerId}`), listener);
     this._firestore.removeListener(this._firestore._getAppEventName(`onDocumentSnapshotError:${listenerId}`), listener);