Implement scopeSubtree for ShadyDOM noPatch mode

Add scopeSubtree as a util function, and use in LegacyElement

lib/legacy/legacy-element-mixin.js

@@ -20,6 +20,7 @@ import { Debouncer } from '../utils/debounce.js';
 import { timeOut, microTask } from '../utils/async.js';
 import { get } from '../utils/path.js';
 import { wrap } from '../utils/wrap.js';
+import { scopeSubtree } from '../utils/scope-subtree.js';
 
 let styleInterface = window.ShadyCSS;
 
@@ -701,12 +702,13 @@ export const LegacyElementMixin = dedupingMixin((base) => {
     /**
      * No-op for backwards compatibility. This should now be handled by
      * ShadyCss library.
-     * @param  {*} container Unused
-     * @param  {*} shouldObserve Unused
-     * @return {void}
+     * @param  {!Element} container Container element to scope
+     * @param  {boolean=} shouldObserve if true, start a mutation observer for added nodes to the container
+     * @return {?MutationObserver} Returns a new MutationObserver on `container` if `shouldObserve` is true.
      * @override
      */
-    scopeSubtree(container, shouldObserve) { // eslint-disable-line no-unused-vars
+    scopeSubtree(container, shouldObserve = false) {
+      return scopeSubtree(container, shouldObserve);
     }
 
     /**

lib/utils/scope-subtree.js

@@ -0,0 +1,76 @@
+/**
+@license
+Copyright (c) 2019 The Polymer Project Authors. All rights reserved.
+This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
+The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
+The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
+Code distributed by Google as part of the polymer project is also
+subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
+*/
+
+import './boot.js';
+import { wrap } from './wrap.js';
+
+const ShadyDOM = window.ShadyDOM;
+const ShadyCSS = window.ShadyCSS;
+
+/**
+ * Ensure that elements in a ShadowDOM container are scoped correctly.
+ *
+ * @param  {!Element} container Container element to scope
+ * @param  {boolean=} shouldObserve if true, start a mutation observer for added nodes to the container
+ * @return {?MutationObserver} Returns a new MutationObserver on `container` if `shouldObserve` is true.
+ */
+export function scopeSubtree(container, shouldObserve = false) {
+  // If using native ShadowDOM, abort
+  if (!ShadyDOM || !ShadyCSS) {
+    return null;
+  }
+  // ShadyCSS handles DOM mutations in patched mode
+  if (!ShadyDOM['noPatch']) {
+    return null;
+  }
+  const ScopingShim = ShadyCSS['ScopingShim'];
+  // if ScopingShim is not available, abort
+  if (!ScopingShim) {
+    return null;
+  }
+  // capture correct scope for container
+  const containerScope = ScopingShim['scopeForNode'](container);
+
+  const scopify = (node) => {
+    const wrappedNode = wrap(node);
+    const elements = [node, ...(wrappedNode.querySelectorAll('*'))];
+    for (let i = 0; i < elements.length; i++) {
+      const el = elements[i];
+      const currentScope = ScopingShim['currentScopeForNode'](el);
+      if (currentScope !== containerScope) {
+        if (currentScope !== '') {
+          ScopingShim['unscopeNode'](el, currentScope);
+        }
+        ScopingShim['scopeNode'](el, containerScope);
+      }
+    }
+  };
+
+  // scope everything in container
+  scopify(container);
+
+  if (shouldObserve) {
+    const mo = new MutationObserver((mxns) => {
+      for (let i = 0; i < mxns.length; i++) {
+        const mxn = mxns[i];
+        for (let j = 0; j < mxn.addedNodes.length; j++) {
+          const addedNode = mxn.addedNodes[j];
+          if (addedNode.nodeType === Node.ELEMENT_NODE) {
+            scopify(addedNode);
+          }
+        }
+      }
+    });
+    mo.observe(container, {childList: true, subtree: true});
+    return mo;
+  } else {
+    return null;
+  }
+}

test/runner.html

@@ -88,7 +88,8 @@
       'unit/html-tag.html',
       'unit/legacy-data.html',
       // 'unit/multi-style.html'
-      'unit/class-properties.html'
+      'unit/class-properties.html',
+      'unit/styling-scoped-nopatch.html'
     ];
 
     function combinations(suites, flags) {

test/unit/styling-scoped-nopatch.html

@@ -0,0 +1,133 @@
+<!doctype html>
+<!--
+@license
+Copyright (c) 2019 The Polymer Project Authors. All rights reserved.
+This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
+The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
+The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
+Code distributed by Google as part of the polymer project is also
+subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
+-->
+<html>
+<head>
+  <meta charset="utf-8">
+  <script>
+    window.ShadyDOM = {force: true, noPatch: true};
+  </script>
+  <script src="../../node_modules/@webcomponents/webcomponentsjs/webcomponents-bundle.js"></script>
+  <script src="wct-browser-config.js"></script>
+  <script src="../../node_modules/wct-browser-legacy/browser.js"></script>
+</head>
+<body>
+
+<script type="module">
+  import {Polymer, html} from '../../polymer-legacy.js';
+  Polymer({
+    is: 'scope-subtree-legacy',
+    _template: html`
+    <style>
+      #container * {
+        border: 10px solid black;
+      }
+    </style>
+    <div id="container"></div>`
+  });
+</script>
+
+<script type="module">
+  import {PolymerElement, html} from '../../polymer-element.js';
+  class ScopeSubtreeElement extends PolymerElement {
+    static get template() {
+      return html`
+        <style>
+          #container * {
+            border: 10px solid black;
+          }
+        </style>
+        <div id="container"></div>`;
+    }
+  }
+  customElements.define('scope-subtree-element', ScopeSubtreeElement);
+</script>
+
+<test-fixture id="legacy">
+  <template>
+    <scope-subtree-legacy></scope-subtree-legacy>
+  </template>
+</test-fixture>
+
+<test-fixture id="element">
+  <template>
+    <scope-subtree-element></scope-subtree-element>
+  </template>
+</test-fixture>
+
+<script type="module">
+  import { scopeSubtree } from '../../lib/utils/scope-subtree.js';
+
+  function assertComputed(element, value, property, pseudo) {
+    var computed = getComputedStyle(element, pseudo);
+    property = property || 'border-top-width';
+    if (Array.isArray(value)) {
+      assert.oneOf(computed[property], value, 'computed style incorrect for ' + property);
+    } else {
+      assert.equal(computed[property], value, 'computed style incorrect for ' + property);
+    }
+  }
+
+  suite('LegacyElement.scopeSubtree', function() {
+    let el;
+    setup(function() {
+      el = fixture('legacy');
+    });
+    test('elements are scoped', function() {
+      const div = document.createElement('div');
+      const innerDiv = document.createElement('div');
+      div.appendChild(innerDiv);
+      el.$.container.appendChild(div);
+      el.scopeSubtree(el.$.container);
+      assertComputed(div, '10px');
+      assertComputed(innerDiv, '10px');
+    });
+    test('second argument creates a mutation observer', async function() {
+      const mo = el.scopeSubtree(el.$.container, true);
+      assert.instanceOf(mo, MutationObserver);
+      const div = document.createElement('div');
+      const innerDiv = document.createElement('div');
+      div.appendChild(innerDiv);
+      el.$.container.appendChild(div);
+      await new Promise((resolve) => setTimeout(resolve, 0));
+      assertComputed(div, '10px');
+      assertComputed(innerDiv, '10px');
+    });
+  });
+
+  suite('PolymerElement and scopeSubtree util', function() {
+    let el;
+    setup(function() {
+      el = fixture('element');
+    });
+    test('elements are scoped', function() {
+      const div = document.createElement('div');
+      const innerDiv = document.createElement('div');
+      div.appendChild(innerDiv);
+      el.$.container.appendChild(div);
+      scopeSubtree(el.$.container);
+      assertComputed(div, '10px');
+      assertComputed(innerDiv, '10px');
+    });
+    test('second argument creates a mutation observer', async function() {
+      const mo = scopeSubtree(el.$.container, true);
+      assert.instanceOf(mo, MutationObserver);
+      const div = document.createElement('div');
+      const innerDiv = document.createElement('div');
+      div.appendChild(innerDiv);
+      el.$.container.appendChild(div);
+      await new Promise((resolve) => setTimeout(resolve, 0));
+      assertComputed(div, '10px');
+      assertComputed(innerDiv, '10px');
+    });
+  });
+</script>
+</body>
+</html>