throw instead of warn.

Author: DellaBitta

packages/firestore/src/api/snapshot.ts

@@ -42,7 +42,6 @@ import {
   QuerySnapshotBundleData
 } from '../util/bundle_builder_impl';
 import { Code, FirestoreError } from '../util/error';
-import { logWarn } from '../util/log';
 import { AutoId } from '../util/misc';
 
 import { Firestore } from './database';
@@ -522,8 +521,10 @@ export class DocumentSnapshot<
       'previous'
     );
     if (documentData.hasPendingWrites) {
-      logWarn(
-        'DocumentSnapshot.toJSON serialized a document with pending writes. The pending writes will not be serialized.'
+      throw new FirestoreError(
+        Code.FAILED_PRECONDITION,
+        'DocumentSnapshot.toJSON attempted to serialize a document with pending writes. ' +
+          'Await `waitForPendingWrites()` before invoking `toJSON()`.'
       );
     }
     builder.addBundleDocument(
@@ -710,8 +711,10 @@ export class QuerySnapshot<
         'previous'
       );
       if (documentData.hasPendingWrites) {
-        logWarn(
-          'QuerySnapshot.toJSON serialized a document with pending writes. The pending writes will not be serialized.'
+        throw new FirestoreError(
+          Code.FAILED_PRECONDITION,
+          'QuerySnapshot.toJSON attempted to serialize a document with pending writes. ' +
+            'Await `waitForPendingWrites()` before invoking `toJSON()`.'
         );
       }
       docBundleDataArray.push(

packages/firestore/src/util/bundle_builder_impl.ts

@@ -46,8 +46,6 @@ import {
 } from '../protos/firestore_proto_api';
 import { AutoId } from '../util/misc';
 
-import { debugAssert } from './assert';
-
 const BUNDLE_VERSION = 1;
 
 /**
@@ -107,9 +105,7 @@ export class BundleBuilder {
       : null;
 
     const neitherHasReadTime: boolean = !docReadTime && origDocReadTime == null;
-    const docIsNewer: boolean =
-      docReadTime !== undefined &&
-      (origDocReadTime == null || origDocReadTime < docReadTime);
+    const docIsNewer: boolean = docReadTime !== undefined && (origDocReadTime == null || origDocReadTime < docReadTime);
     if (neitherHasReadTime || docIsNewer) {
       // Store document.
       this.documents.set(docBundleData.documentPath, {
@@ -122,7 +118,7 @@ export class BundleBuilder {
           exists: docBundleData.documentExists
         }
       });
-    }
+    } 
     if (docReadTime && docReadTime > this.latestReadTime) {
       this.latestReadTime = docReadTime;
     }