Issue 6437 - Skip styles-only patterns on DOM mutations

lib/content/elemHideEmulation.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 "use strict";
 
 const {textToRegExp, filterToRegExp, splitSelector} = require("../common");
 
 let MIN_INVOCATION_INTERVAL = 3000;
 const MAX_SYNCHRONOUS_PROCESSING_TIME = 50;
 const abpSelectorRegexp = /:-abp-([\w-]+)\(/i;
 
+function getCachedPropertyValue(object, name, defaultValueFunc = () => {})
+{
+  let value = object[name];
+  if (typeof value == "undefined")
+    Object.defineProperty(object, name, {value: value = defaultValueFunc()});
+  return value;
+}
+
 /** Return position of node from parent.
  * @param {Node} node the node to find the position of.
  * @return {number} One-based index like for :nth-child(), or 0 on error.
  */
 function positionInParent(node)
 {
   let {children} = node.parentNode;
   for (let i = 0; i < children.length; i++)
     if (children[i] == node)
       return i + 1;
@@ skipping 336 matching lines @@
         }
   },
 
   *getSelectors(prefix, subtree, styles)
   {
     for (let selector of this.findPropsSelectors(styles, prefix, this._regexp))
       yield [selector, subtree];
   }
 };
 
-function isSelectorHidingOnlyPattern(pattern)
-{
-  return pattern.selectors.some(s => s.preferHideWithSelector) &&
-    !pattern.selectors.some(s => s.requiresHiding);
-}
-
-function patternDependsOnStyles(pattern)
-{
-  return pattern.selectors.some(s => s.dependsOnStyles);
-}
-
-function patternDependsOnDOM(pattern)
-{
-  return pattern.selectors.some(s => s.dependsOnDOM);
-}
-
-function patternDependsOnStylesAndDOM(pattern)
-{
-  return pattern.selectors.some(s => s.dependsOnStyles && s.dependsOnDOM);
-}
+function Pattern(selectors, text)
+{
+  this.selectors = selectors;
+  this.text = text;
+}
+
+Pattern.prototype = {
+  isSelectorHidingOnlyPattern()
+  {
+    return getCachedPropertyValue(
+      this, "_selectorHidingOnlyPattern",
+      () => this.selectors.some(selector => selector.preferHideWithSelector) &&
+            !this.selectors.some(selector => selector.requiresHiding)
+    );
+  },
+
+  get dependsOnStyles()
+  {
+    return getCachedPropertyValue(
+      this, "_dependsOnStyles",
+      () => this.selectors.some(selector => selector.dependsOnStyles)
+    );
+  },
+
+  get dependsOnDOM()
+  {
+    return getCachedPropertyValue(
+      this, "_dependsOnDOM",
+      () => this.selectors.some(selector => selector.dependsOnDOM)
+    );
+  },
+
+  get dependsOnStylesAndDOM()
+  {
+    return getCachedPropertyValue(
+      this, "_dependsOnStylesAndDOM",
+      () => this.selectors.some(selector => selector.dependsOnStyles &&
+                                            selector.dependsOnDOM)
+    );
+  },
+
+  get maybeDependsOnAttributes()
+  {
+    // Observe changes to attributes if either there's a plain selector that
+    // looks like an ID selector, class selector, or attribute selector in one
+    // of the patterns (e.g. "a[href='https://example.com/']")
+    // or there's a properties selector nested inside a has selector
+    // (e.g. "div:-abp-has(:-abp-properties(color: blue))")
+    return getCachedPropertyValue(
+      this, "_maybeDependsOnAttributes",
+      () => this.selectors.some(
+              selector => selector.maybeDependsOnAttributes ||
+                          (selector instanceof HasSelector &&
+                           selector.dependsOnStyles)
+            )
+    );
+  },
+
+  get dependsOnCharacterData()
+  {
+    // Observe changes to character data only if there's a contains selector in
+    // one of the patterns.
+    return getCachedPropertyValue(
+      this, "_dependsOnCharacterData",
+      () => this.selectors.some(selector => selector.dependsOnCharacterData)
+    );
+  }
+};
 
 function filterPatterns(patterns, {stylesheets, mutations})
 {
-  if (stylesheets && !mutations)
-    return patterns.filter(patternDependsOnStyles);
-
-  if (!stylesheets && mutations)
-    return patterns.filter(patternDependsOnDOM);
-
-  return patterns.slice();
+  if (!stylesheets && !mutations)
+    return patterns.slice();
+
+  return patterns.filter(
+    pattern => (stylesheets && pattern.dependsOnStyles) ||
+               (mutations && pattern.dependsOnDOM)
+  );
 }
 
 function shouldObserveAttributes(patterns)
 {
-  // Observe changes to attributes if either there's a plain selector that
-  // looks like an ID selector, class selector, or attribute selector in one of
-  // the patterns (e.g. "a[href='https://example.com/']")
-  // or there's a properties selector nested inside a has selector
-  // (e.g. "div:-abp-has(:-abp-properties(color: blue))")
-  return patterns.some(
-    pattern => pattern.selectors.some(
-      selector => selector.maybeDependsOnAttributes ||
-                  (selector instanceof HasSelector &&
-                   selector.dependsOnStyles)
-    )
-  );
+  return patterns.some(pattern => pattern.maybeDependsOnAttributes);
 }
 
 function shouldObserveCharacterData(patterns)
 {
-  // Observe changes to character data only if there's a contains selector in
-  // one of the patterns.
-  return patterns.some(
-    pattern => pattern.selectors.some(
-      selector => selector.dependsOnCharacterData
-    )
-  );
+  return patterns.some(pattern => pattern.dependsOnCharacterData);
 }
 
 function ElemHideEmulation(addSelectorsFunc, hideElemsFunc)
 {
   this.document = document;
   this.addSelectorsFunc = addSelectorsFunc;
   this.hideElemsFunc = hideElemsFunc;
   this.observer = new MutationObserver(this.observe.bind(this));
 }
 
@@ skipping 105 matching lines @@
     // do full processing.
     if (!stylesheets && !mutations)
       stylesheets = this.document.styleSheets;
 
     // If there are any DOM mutations and any of the patterns depends on both
     // style sheets and the DOM (e.g. -abp-has(-abp-properties)), find all the
     // rules in every style sheet in the document, because we need to run
     // querySelectorAll afterwards. On the other hand, if we only have patterns
     // that depend on either styles or DOM both not both
     // (e.g. -abp-properties or -abp-contains), we can skip this part.
-    if (mutations && patterns.some(patternDependsOnStylesAndDOM))
+    if (mutations && patterns.some(pattern => pattern.dependsOnStylesAndDOM))
       stylesheets = this.document.styleSheets;
 
     for (let stylesheet of stylesheets || [])
     {
       // Explicitly ignore third-party stylesheets to ensure consistent behavior
       // between Firefox and Chrome.
       if (!this.isSameOrigin(stylesheet))
         continue;
 
       let rules = stylesheet.cssRules;
@@ skipping 13 matching lines @@
     let generator = null;
 
     let processPatterns = () =>
     {
       let cycleStart = performance.now();
 
       if (!pattern)
       {
         if (!patterns.length)
         {
-          this.addSelectorsFunc(selectors, selectorFilters);
-          this.hideElemsFunc(elements, elementFilters);
+          if (selectors.length > 0)
+            this.addSelectorsFunc(selectors, selectorFilters);
+          if (elements.length > 0)
+            this.hideElemsFunc(elements, elementFilters);
           if (typeof done == "function")
             done();
           return;
         }
 
         pattern = patterns.shift();
 
         generator = evaluate(pattern.selectors, 0, "",
                              this.document, cssStyles);
       }
       for (let selector of generator)
       {
         if (selector != null)
         {
-          if (isSelectorHidingOnlyPattern(pattern))
+          if (pattern.isSelectorHidingOnlyPattern())
           {
             selectors.push(selector);
             selectorFilters.push(pattern.text);
           }
           else
           {
             for (let element of this.document.querySelectorAll(selector))
             {
               elements.push(element);
               elementFilters.push(pattern.text);
@@ skipping 39 matching lines @@
    *    for full reprocessing.
    */
   queueFiltering(stylesheets, mutations)
   {
     let completion = () =>
     {
       this._lastInvocation = performance.now();
       this._filteringInProgress = false;
       if (this._scheduledProcessing)
       {
-        let {stylesheets, mutations} = this._scheduledProcessing;
+        let params = Object.assign({}, this._scheduledProcessing);
         this._scheduledProcessing = null;
-        this.queueFiltering(stylesheets, mutations);
+        this.queueFiltering(params.stylesheets, params.mutations);
       }
     };
 
     if (this._scheduledProcessing)
     {
       if (!stylesheets && !mutations)
       {
         this._scheduledProcessing = {};
       }
       else
@@ skipping 14 matching lines @@
     }
     else if (this._filteringInProgress)
     {
       this._scheduledProcessing = {stylesheets, mutations};
     }
     else if (performance.now() - this._lastInvocation < MIN_INVOCATION_INTERVAL)
     {
       this._scheduledProcessing = {stylesheets, mutations};
       setTimeout(() =>
       {
-        let {stylesheets, mutations} = this._scheduledProcessing;
+        let params = Object.assign({}, this._scheduledProcessing);
         this._filteringInProgress = true;
         this._scheduledProcessing = null;
-        this._addSelectors(stylesheets, mutations, completion);
+        this._addSelectors(params.stylesheets, params.mutations, completion);
       },
       MIN_INVOCATION_INTERVAL - (performance.now() - this._lastInvocation));
     }
     else if (this.document.readyState == "loading")
     {
       this._scheduledProcessing = {stylesheets, mutations};
       let handler = () =>
       {
         document.removeEventListener("DOMContentLoaded", handler);
-        let {stylesheets, mutations} = this._scheduledProcessing;
+        let params = Object.assign({}, this._scheduledProcessing);
         this._filteringInProgress = true;
         this._scheduledProcessing = null;
-        this._addSelectors(stylesheets, mutations, completion);
+        this._addSelectors(params.stylesheets, params.mutations, completion);
       };
       document.addEventListener("DOMContentLoaded", handler);
     }
     else
     {
       this._filteringInProgress = true;
       this._addSelectors(stylesheets, mutations, completion);
     }
   },
 
   onLoad(event)
   {
     let stylesheet = event.target.sheet;
     if (stylesheet)
       this.queueFiltering([stylesheet]);
   },
 
   observe(mutations)
   {
     this.queueFiltering(null, mutations);
   },
 
   apply(patterns)
   {
     this.patterns = [];
     for (let pattern of patterns)
     {
       let selectors = this.parseSelector(pattern.selector);
       if (selectors != null && selectors.length > 0)
-        this.patterns.push({selectors, text: pattern.text});
+        this.patterns.push(new Pattern(selectors, pattern.text));
     }
 
     if (this.patterns.length > 0)
     {
       this.queueFiltering();
       this.observer.observe(
         this.document,
         {
           childList: true,
           attributes: shouldObserveAttributes(this.patterns),
           characterData: shouldObserveCharacterData(this.patterns),
           subtree: true
         }
       );
       this.document.addEventListener("load", this.onLoad.bind(this), true);
     }
   }
 };
 
 exports.ElemHideEmulation = ElemHideEmulation;