ref: move PureWidget back to core, use updateEnv

src/component.ts

@@ -407,3 +407,21 @@ export class Component<
     }
   }
 }
+
+export class PureComponent<E extends Env, P, S> extends Component<E, P, S> {
+  shouldUpdate(nextProps: P): boolean {
+    for (let k in nextProps) {
+      if (nextProps[k] !== this.props[k]) {
+        return true;
+      }
+    }
+    return false;
+  }
+  async updateState(nextState: Partial<S>) {
+    for (let k in nextState) {
+      if (nextState[k] !== this.state[k]) {
+        return super.updateState(nextState);
+      }
+    }
+  }
+}