[cloud_firestore] ios ceck for nil snapshot in cloud_firestore error …

…handling instead of checking for non-nil error (flutter#1339)

* Check for nil snapshot in cloud_firestore error handling instead of checking for non-nil error

packages/cloud_firestore/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 0.9.6
+
+* On iOS, update null checking to match the recommended pattern usage in the Firebase documentation.
+* Fixes a case where snapshot errors might result in plugin crash.
+
 ## 0.9.5+2
 
 * Fixing PlatformException(Error 0, null, null) which happened when a successful operation was performed.

packages/cloud_firestore/ios/Classes/CloudFirestorePlugin.m

@@ -390,7 +390,7 @@ - (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result
     FIRDocumentReference *document = getDocumentReference(call.arguments);
     [document getDocumentWithCompletion:^(FIRDocumentSnapshot *_Nullable snapshot,
                                           NSError *_Nullable error) {
-      if (error) {
+      if (snapshot == nil) {
         result(getFlutterError(error));
       } else {
         result(@{
@@ -411,7 +411,7 @@ - (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result
     }
     id<FIRListenerRegistration> listener = [query
         addSnapshotListener:^(FIRQuerySnapshot *_Nullable snapshot, NSError *_Nullable error) {
-          if (error) {
+          if (snapshot == nil) {
             result(getFlutterError(error));
             return;
           }
@@ -426,7 +426,7 @@ - (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result
     FIRDocumentReference *document = getDocumentReference(call.arguments);
     id<FIRListenerRegistration> listener =
         [document addSnapshotListener:^(FIRDocumentSnapshot *snapshot, NSError *_Nullable error) {
-          if (error) {
+          if (snapshot == nil) {
             result(getFlutterError(error));
             return;
           }
@@ -450,7 +450,10 @@ - (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result
     }
     [query getDocumentsWithCompletion:^(FIRQuerySnapshot *_Nullable snapshot,
                                         NSError *_Nullable error) {
-      if (error) result(getFlutterError(error));
+      if (snapshot != nil) {
+        result(getFlutterError(error));
+        return;
+      }
       result(parseQuerySnapshot(snapshot));
     }];
   } else if ([@"Query#removeListener" isEqualToString:call.method]) {

packages/cloud_firestore/pubspec.yaml

@@ -3,7 +3,7 @@ description: Flutter plugin for Cloud Firestore, a cloud-hosted, noSQL database
   live synchronization and offline support on Android and iOS.
 author: Flutter Team <[email protected]>
 homepage: https://github.com/flutter/plugins/tree/master/packages/cloud_firestore
-version: 0.9.5+2
+version: 0.9.6
 
 flutter:
   plugin: