fix(firestore, web): fix an issue where nested object could be incorr…

…ectly decoded from JSObjects (#12289)

packages/cloud_firestore/cloud_firestore/example/integration_test/field_value_e2e.dart

@@ -207,6 +207,24 @@ void runFieldValueTests() {
         expect(snapshot.data()!['timestamp'], isA<Timestamp>());
         expect(snapshot.data()!['nested']['timestamp'], isA<Timestamp>());
       });
+
+      testWidgets('query should restore nested Timestamp in List', (_) async {
+        DocumentReference<Map<String, dynamic>> doc =
+            await initializeTest('nested-timestamp');
+        await doc.set({
+          'timestamp': Timestamp.fromDate(DateTime.now()),
+          'logs': [
+            {
+              'createdAt': Timestamp.fromDate(DateTime.now()),
+            },
+          ],
+        });
+
+        final snapshot = await doc.get();
+
+        expect(snapshot.data()!['timestamp'], isA<Timestamp>());
+        expect(snapshot.data()!['logs'][0]['createdAt'], isA<Timestamp>());
+      });
     });
   });
 }

packages/cloud_firestore/cloud_firestore_web/lib/src/interop/utils/utils.dart

@@ -11,6 +11,7 @@ import '../firestore.dart';
 
 /// Returns Dart representation from JS Object.
 dynamic dartify(dynamic object) {
+  // Convert JSObject to Dart equivalents directly
   if (object is! JSObject) {
     return object;
   }
@@ -32,28 +33,24 @@ dynamic dartify(dynamic object) {
     return jsObject as BytesJsImpl;
   }
 
+  // Convert nested structures
   final dartObject = jsObject.dartify();
-  if (dartObject is List) {
-    return dartObject.map(dartify).toList();
-  }
+  return convertNested(dartObject);
+}
 
-  if (dartObject is Map) {
-    final Map<String, dynamic> map = {};
-    for (final key in dartObject.keys) {
-      final value = dartObject[key];
-      if (value is Map) {
-        map[key as String] =
-            value.map((key, value) => MapEntry(key, dartify(value)));
-      } else if (value is List) {
-        map[key as String] = value.map(dartify).toList();
-      } else {
-        map[key as String] = dartify(value);
-      }
-    }
+dynamic convertNested(dynamic object) {
+  if (object is List) {
+    return object.map(convertNested).toList();
+  } else if (object is Map) {
+    var map = <String, dynamic>{};
+    object.forEach((key, value) {
+      map[key] = convertNested(value);
+    });
     return map;
+  } else {
+    // For non-nested types, attempt to convert directly
+    return dartify(object);
   }
-
-  return dartObject;
 }
 
 /// Returns the JS implementation from Dart Object.