Shady Parts: improved support for mutations, plus small bugfixes

packages/shadycss/externs/shadycss-externs.js

@@ -10,6 +10,8 @@
  * flushCustomStyles: function(),
  * getComputedStyleValue: function(!Element, string): string,
  * onInsertBefore: function(!HTMLElement, !HTMLElement, ?HTMLElement): void,
+ * onSetAttribute: function(!HTMLElement, !string, !string, ?string): void,
+ * onRemoveAttribute: function(!HTMLElement, !string): void,
  * ScopingShim: (Object|undefined),
  * ApplyShim: (Object|undefined),
  * CustomStyleInterface: (Object|undefined),

packages/shadycss/src/common-utils.js

@@ -12,6 +12,13 @@ subject to an additional IP rights grant found at http://polymer.github.io/PATEN
 
 import { MIXIN_MATCH, VAR_ASSIGN } from './common-regex.js';
 
+/**
+ * The prefix used by ShadyDOM for the native version of patched methods
+ * (e.g. `__shady_native_setAttribute`).
+ * @type {!string}
+ */
+export const NATIVE_PREFIX = '__shady_native_';
+
 /**
  * @param {Element} element
  * @param {Object=} properties

packages/shadycss/src/scoping-shim.js

@@ -295,6 +295,51 @@ export default class ScopingShim {
     }
   }
 
+  /* eslint-disable no-unused-vars */
+
+  /**
+   * Hook for performing ShadyCSS updates after a relevant attribute is set.
+   * Note ShadyDOM will only call this function for "part" and "exportparts"
+   * attributes.
+   *
+   * @param {!HTMLElement} element Element
+   * @param {!string} name Attribute name.
+   * @param {!string} newValue New attribute value.
+   * @param {?string} oldValue Old attribute value or null if was unset.
+   * @return {void}
+   */
+  onSetAttribute(element, name, newValue, oldValue) {
+    if (!disableShadowParts) {
+      if (name === 'part') {
+        shadowParts.onSetPartAttribute(element);
+      } else if (name === 'exportparts') {
+        shadowParts.onSetExportPartsAttribute(element, newValue, oldValue);
+      }
+    }
+  }
+
+  /* eslint-enable no-unused-vars */
+
+  /**
+   * Hook for performing ShadyCSS updates after a relevant attribute is removed.
+   * Note ShadyDOM will only call this function for "part" and "exportparts"
+   * attributes.
+   *
+   * @param {!HTMLElement} element Element
+   * @param {!string} name Attribute name.
+   * @param {!string} oldValue Old attribute value.
+   * @return {void}
+   */
+  onRemoveAttribute(element, name, oldValue) {
+    if (!disableShadowParts) {
+      if (name === 'part') {
+        shadowParts.onRemovePartAttribute(element);
+      } else if (name === 'exportparts') {
+        shadowParts.onRemoveExportPartsAttribute(element, oldValue);
+      }
+    }
+  }
+
   /**
    * Apply styles for the given element
    *