fix(database): generate 0-based childKeys for List values in MethodChannelDataSnapshot.

packages/firebase_database/firebase_database/example/integration_test/data_snapshot_e2e.dart

@@ -177,5 +177,20 @@ void setupDataSnapshotTests() {
       expect(children[1].value, 2);
       expect(children[2].value, 3);
     });
+
+    test('children returns the children for a nested list snapshot', () async {
+      final ref = getRef('nested-list-children');
+      await ref.set({
+        'items': ['first', 'second', 'third'],
+      });
+      final s = await ref.get();
+
+      final children = s.child('items').children.toList();
+      expect(children.map((c) => c.key).toList(), ['0', '1', '2']);
+      expect(
+        children.map((c) => c.value).toList(),
+        ['first', 'second', 'third'],
+      );
+    });
   });
 }

packages/firebase_database/firebase_database_platform_interface/lib/src/method_channel/method_channel_data_snapshot.dart

@@ -104,7 +104,7 @@ List<String> _childKeysFromValue(Object? value) {
   } else if (value is List) {
     childChildKeys = List<String>.generate(
       value.length,
-      (int index) => '${index - 1}',
+      (int index) => '$index',
     );
   }
   return childChildKeys;

packages/firebase_database/firebase_database_platform_interface/test/method_channel_test.dart

@@ -6,6 +6,7 @@ import 'dart:async';
 
 import 'package:firebase_core/firebase_core.dart';
 import 'package:firebase_database_platform_interface/firebase_database_platform_interface.dart';
+import 'package:firebase_database_platform_interface/src/method_channel/method_channel_data_snapshot.dart';
 import 'package:firebase_database_platform_interface/src/method_channel/method_channel_database.dart';
 import 'package:firebase_database_platform_interface/src/method_channel/method_channel_database_reference.dart';
 import 'package:firebase_database_platform_interface/src/pigeon/messages.pigeon.dart'
@@ -563,6 +564,33 @@ void main() {
         );
       });
     });
+
+    group('MethodChannelDataSnapshot', () {
+      test(
+          'child() on a List-valued child generates 0-based childKeys and iterates children without RangeError',
+          () {
+        final snapshot = MethodChannelDataSnapshot(
+          database.ref('root'),
+          <String, dynamic>{
+            'key': 'root',
+            'value': <String, dynamic>{
+              'items': <Object?>['first', 'second', 'third'],
+            },
+            'priority': null,
+            'childKeys': <String>['items'],
+          },
+        );
+
+        final itemsSnapshot = snapshot.child('items');
+        final children = itemsSnapshot.children.toList();
+
+        expect(children.map((c) => c.key).toList(), <String>['0', '1', '2']);
+        expect(
+          children.map((c) => c.value).toList(),
+          <Object?>['first', 'second', 'third'],
+        );
+      });
+    });
   });
 }