Placeholders read JSON without empty allowedTypes/deniedTypes

CHANGELOG.md

@@ -108,6 +108,9 @@
 
 ### Fixes
 
+- Placeholders (variances, lists, grids, pages) read JSON that leaves out
+  empty `allowedTypes` or `deniedTypes`, as JSON written before this
+  release could.
 - `SpacerNode.fromJson` defaults `positioningMode` (align),
   `aspectRatioLock` (false) and `reactions` ([]) like every other node, and
   `GridViewNode.fromJson` defaults `isScrollable` (true) and

lib/src/api/nodes/single_placeholder_node.dart

@@ -34,12 +34,14 @@ class SinglePlaceholderNode extends SceneNode
   /// The node types that are allowed to be inside this [SinglePlaceholderNode].
   /// Example: 'APP_BAR' for AppBarNode.
   /// When empty, allow all types.
+  @JsonKey(readValue: readTypesOrEmpty)
   List<String> allowedTypes;
 
   /// The node types that are not allowed to be inside this
   /// [SinglePlaceholderNode].
   /// Example: "TEXT" for TextNode.
   /// When empty, allow all types.
+  @JsonKey(readValue: readTypesOrEmpty)
   List<String> deniedTypes;
 
   /// If not null, this [SinglePlaceholderNode] will only accept nodes that do
@@ -89,3 +91,7 @@ class SinglePlaceholderNode extends SceneNode
     _$SinglePlaceholderNodeToJson(this),
   );
 }
+
+/// Reads [allowedTypes] or [deniedTypes] from [json], an empty list when the
+/// key is missing: JSON that leaves empty lists out still reads.
+Object? readTypesOrEmpty(Map json, String key) => json[key] ?? const <String>[];

test/placeholder_types_missing_test.dart

@@ -0,0 +1,37 @@
+import 'package:codelessly_api/codelessly_api.dart';
+import 'package:test/test.dart';
+
+void main() {
+  test('placeholders read JSON that leaves out empty type lists', () {
+    for (final String type in ['variance', 'listView', 'gridView']) {
+      final Map<String, dynamic> json = {
+        'type': type,
+        'id': 'x',
+        'name': 'n',
+        'basicBoxLocal': [0, 0, 100, 100],
+        'children': <String>[],
+        'properties': <String, dynamic>{},
+        if (type == 'variance') ...{
+          'variants': [
+            {'id': 'default', 'name': 'Default', 'children': <String>[]},
+          ],
+          'currentVariantId': 'default',
+        },
+        if (type == 'gridView')
+          'properties': {
+            'gridDelegate': {
+              'type': 'fixedCrossAxisCount',
+              'crossAxisCount': 2,
+            },
+          },
+      };
+      json.remove('allowedTypes');
+      json.remove('deniedTypes');
+      final node = NodeJsonConverter().fromJson(json) as SinglePlaceholderNode;
+      expect(node.allowedTypes, isEmpty, reason: type);
+      // A list keeps its own default; a variance reads it as empty.
+      if (type == 'variance') expect(node.deniedTypes, isEmpty);
+      if (type == 'listView') expect(node.deniedTypes, ['listView']);
+    }
+  });
+}