Implement PureComponent

Author: aaronlademann-wf

lib/react.dart

@@ -7,6 +7,7 @@
 /// A Dart library for building UI using ReactJS.
 library react;
 
+import 'package:collection/equality.dart';
 import 'package:meta/meta.dart';
 import 'package:react/react_client/bridge.dart';
 import 'package:react/src/prop_validator.dart';
@@ -1230,6 +1231,28 @@ abstract class Component2 implements Component {
   _initProps(props) {}
 }
 
+/// Top-level ReactJS [PureComponent class](https://reactjs.org/docs/react-api.html#reactpurecomponent)
+abstract class PureComponent extends Component2 {
+  @mustCallSuper
+  @override
+  bool shouldComponentUpdate(Map nextProps, Map nextState) {
+    return !PureComponent._shallowPropsEqual(props, nextProps) || !PureComponent._shallowStateEqual(state, nextState);
+  }
+
+  static bool _shallowPropsEqual(Map map1, Map map2) {
+    // Does this work, or does props.children always make this return false?
+    return MapEquality().equals(
+          Map.of(map1)..remove('key')..remove('ref')..remove('children'),
+          Map.of(map2)..remove('key')..remove('ref')..remove('children'),
+        ) &&
+        ListEquality().equals(map1['children'], map2['children']);
+  }
+
+  static bool _shallowStateEqual(Map map1, Map map2) {
+    return MapEquality().equals(map1, map2);
+  }
+}
+
 /// Mixin that enforces consistent typing of the `snapshot` parameter
 /// returned by [Component2.getSnapshotBeforeUpdate]
 /// and passed into [Component2.componentDidUpdate].

pubspec.yaml

@@ -13,6 +13,7 @@ homepage: https://github.com/cleandart/react-dart
 environment:
   sdk: '>=2.4.0 <3.0.0'
 dependencies:
+  collection: ^1.14.12
   js: ^0.6.0
   meta: ^1.1.6
 dev_dependencies: