Issue 5079 - Turn elemHideEmulation into a CommonJS module

lib/content/elemHideEmulation.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2017 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/>.
  */
 
-/* eslint-env browser */

[kzar, 2017/06/12 12:50:13]

Why is this necessary?

[hub, 2017/06/12 13:26:33]

The mistake here is that I should have the proper .eslintrc instead. Will fix
that.

We definitely need the browser env.

[kzar, 2017/06/12 13:35:12]

Sorry, but I still don't understand why it's necessary?

[hub, 2017/06/12 14:03:14]

This change is gone in the current version of the patch I use the .eslintrc.json
that was in chrome/content

It is necessary as we run in the browser environment where the `document` and
`console` globals are defined. This is just carrying over from the existing
code.

[kzar, 2017/06/12 14:12:44]

Right now I understand, previously this file was ignored by ESLint but it has
been renamed. I guess the old name should be removed from .eslintignore now.

Also I seem to remember Wladimir disagreeing that the browser env should be
added globally, but I can't remember why. I'll ask in IRC.

[hub, 2017/06/12 15:21:50]

This is now totally gone in the current patch since the ancestor patches
actually address the problem (an actual bug)

-/* globals filterToRegExp */
-
 "use strict";
 
+const {filterToRegExp} = require("common");
+
+const MIN_INVOCATION_INTERVAL = 3000;
 const abpSelectorRegexp = /:-abp-([\w-]+)\(/i;
 
 function splitSelector(selector)
 {
   if (selector.indexOf(",") == -1)
     return [selector];
 
   let selectors = [];
   let start = 0;
   let level = 0;
@@ skipping 87 matching lines @@
     {
       parens--;
       if (parens == 0)
         break;
     }
   }
 
   if (parens > 0)
     return null;
   return {text: content.substring(startIndex, i), end: i};
-}
-
-/** Parse the selector
- * @param {string} selector the selector to parse
- * @return {Object} selectors is an array of objects,
- * or null in case of errors. hide is true if we'll hide
- * elements instead of styles..
- */
-function parseSelector(selector)
-{
-  if (selector.length == 0)
-    return [];
-
-  let match = abpSelectorRegexp.exec(selector);
-  if (!match)
-    return [new PlainSelector(selector)];
-
-  let selectors = [];
-  if (match.index > 0)
-    selectors.push(new PlainSelector(selector.substr(0, match.index)));
-
-  let startIndex = match.index + match[0].length;
-  let content = parseSelectorContent(selector, startIndex);
-  if (!content)
-  {
-    console.error(new SyntaxError("Failed parsing content filter " +
-                                  `selector ${selector}, didn't ` +
-                                  "find closing parenthesis."));
-    return null;
-  }
-  if (match[1] == "properties")
-    selectors.push(new PropsSelector(content.text));
-  else if (match[1] == "has")
-  {
-    let hasSelector = new HasSelector(content.text);
-    if (!hasSelector.valid())
-      return null;
-    selectors.push(hasSelector);
-  }
-  else if (match[1] == "contains")
-    selectors.push(new ContainsSelector(content.text));
-  else
-  {
-    // this is an error, can't parse selector.
-    console.error(new SyntaxError("Failed parsing content filter " +
-                                  `selector ${selector}, invalid ` +
-                                  `pseudo-class -abp-${match[1]}().`));
-    return null;
-  }
-
-  let suffix = parseSelector(selector.substr(content.end + 1));
-  if (suffix == null)
-    return null;
-
-  selectors.push(...suffix);
-
-  return selectors;
 }
 
 /** Stringified style objects
  * @typedef {Object} StringifiedStyle
  * @property {string} style CSS style represented by a string.
  * @property {string[]} subSelectors selectors the CSS properties apply to.
  */
 
 /**
  * Produce a string representation of the stylesheet entry.
@@ skipping 43 matching lines @@
    * @param {StringifiedStyle[]} styles the stringified style objects.
    */
   *getSelectors(prefix, subtree, styles)
   {
     yield [prefix + this._selector, subtree];
   }
 };
 
 const incompletePrefixRegexp = /[\s>+~]$/;
 
-function HasSelector(selector)
-{
-  this._innerSelectors = parseSelector(selector);
+function HasSelector(selectors)
+{
+  this._innerSelectors = selectors;
 }
 
 HasSelector.prototype = {
   requiresHiding: true,
 
-  valid()
-  {
-    return this._innerSelectors != null;
+  get dependsOnStyles()
+  {
+    return this._innerSelectors.some(selector => selector.dependsOnStyles);
   },
 
   *getSelectors(prefix, subtree, styles)
   {
     for (let element of this.getElements(prefix, subtree, styles))
       yield [makeSelector(element, ""), element];
   },
 
   /**
    * Generator function returning selected elements.
    * @param {string} prefix the prefix for the selector.
    * @param {Node} subtree the subtree we work on.
    * @param {StringifiedStyle[]} styles the stringified style objects.
    */
   *getElements(prefix, subtree, styles)
   {
     let actualPrefix = (!prefix || incompletePrefixRegexp.test(prefix)) ?
         prefix + "*" : prefix;
     let elements = subtree.querySelectorAll(actualPrefix);
     for (let element of elements)
     {
-      let newPrefix = makeSelector(element, "");
-      let iter = evaluate(this._innerSelectors, 0, newPrefix + " ",
-                          element, styles);
+      let iter = evaluate(this._innerSelectors, 0, "", element, styles);
       for (let selector of iter)
-        // we insert a space between the two. It becomes a no-op if selector
-        // doesn't have a combinator
-        if (subtree.querySelector(selector))
+        if (element.querySelector(selector))
           yield element;
     }
   }
 };
 
 function ContainsSelector(textContent)
 {
   this._text = textContent;
 }
 
 ContainsSelector.prototype = {
   requiresHiding: true,
 
   *getSelectors(prefix, subtree, stylesheet)
   {
     for (let element of this.getElements(prefix, subtree, stylesheet))
       yield [makeSelector(element, ""), subtree];
   },
 
   *getElements(prefix, subtree, stylesheet)
   {
     let actualPrefix = (!prefix || incompletePrefixRegexp.test(prefix)) ?
         prefix + "*" : prefix;
     let elements = subtree.querySelectorAll(actualPrefix);
     for (let element of elements)
-      if (element.textContent == this._text)
+      if (element.textContent.includes(this._text))
         yield element;
   }
 };
 
 function PropsSelector(propertyExpression)
 {
   let regexpString;
   if (propertyExpression.length >= 2 && propertyExpression[0] == "/" &&
       propertyExpression[propertyExpression.length - 1] == "/")
   {
     regexpString = propertyExpression.slice(1, -1)
       .replace("\\x7B ", "{").replace("\\x7D ", "}");
   }
   else
     regexpString = filterToRegExp(propertyExpression);
 
   this._regexp = new RegExp(regexpString, "i");
 }
 
 PropsSelector.prototype = {
+  preferHideWithSelector: true,
+  dependsOnStyles: true,
+
   *findPropsSelectors(styles, prefix, regexp)
   {
     for (let style of styles)
       if (regexp.test(style.style))
         for (let subSelector of style.subSelectors)
+        {
+          let idx = subSelector.lastIndexOf("::");
+          if (idx != -1)
+            subSelector = subSelector.substr(0, idx);
           yield prefix + subSelector;
+        }
   },
 
   *getSelectors(prefix, subtree, styles)
   {
     for (let selector of this.findPropsSelectors(styles, prefix, this._regexp))
       yield [selector, subtree];
   }
 };
 
 function ElemHideEmulation(window, getFiltersFunc, addSelectorsFunc,
@@ skipping 12 matching lines @@
     {
       return new URL(stylesheet.href).origin == this.window.location.origin;
     }
     catch (e)
     {
       // Invalid URL, assume that it is first-party.
       return true;
     }
   },
 
+  /** Parse the selector
+   * @param {string} selector the selector to parse
+   * @return {Array} selectors is an array of objects,
+   * or null in case of errors.
+   */
+  parseSelector(selector)
+  {
+    if (selector.length == 0)
+      return [];
+
+    let match = abpSelectorRegexp.exec(selector);
+    if (!match)
+      return [new PlainSelector(selector)];
+
+    let selectors = [];
+    if (match.index > 0)
+      selectors.push(new PlainSelector(selector.substr(0, match.index)));
+
+    let startIndex = match.index + match[0].length;
+    let content = parseSelectorContent(selector, startIndex);
+    if (!content)
+    {
+      this.window.console.error(
+        new SyntaxError("Failed to parse Adblock Plus " +
+                        `selector ${selector} ` +
+                        "due to unmatched parentheses."));
+      return null;
+    }
+    if (match[1] == "properties")
+      selectors.push(new PropsSelector(content.text));
+    else if (match[1] == "has")
+    {
+      let hasSelectors = this.parseSelector(content.text);
+      if (hasSelectors == null)
+        return null;
+      selectors.push(new HasSelector(hasSelectors));
+    }
+    else if (match[1] == "contains")
+      selectors.push(new ContainsSelector(content.text));
+    else
+    {
+      // this is an error, can't parse selector.
+      this.window.console.error(
+        new SyntaxError("Failed to parse Adblock Plus " +
+                        `selector ${selector}, invalid ` +
+                        `pseudo-class :-abp-${match[1]}().`));
+      return null;
+    }
+
+    let suffix = this.parseSelector(selector.substr(content.end + 1));
+    if (suffix == null)
+      return null;
+
+    selectors.push(...suffix);
+
+    if (selectors.length == 1 && selectors[0] instanceof ContainsSelector)
+    {
+      this.window.console.error(
+        new SyntaxError("Failed to parse Adblock Plus " +
+                        `selector ${selector}, can't ` +
+                        "have a lonely :-abp-contains()."));
+      return null;
+    }
+    return selectors;
+  },
+
+  _lastInvocation: 0,
+
+  /**
+   * Processes the current document and applies all rules to it.
+   * @param {CSSStyleSheet[]} [stylesheets]
+   *    The list of new stylesheets that have been added to the document and
+   *    made reprocessing necessary. This parameter shouldn't be passed in for
+   *    the initial processing, all of document's stylesheets will be considered
+   *    then and all rules, including the ones not dependent on styles.
+   */
   addSelectors(stylesheets)
   {
+    this._lastInvocation = Date.now();
+
     let selectors = [];
     let selectorFilters = [];
 
     let elements = [];
     let elementFilters = [];
 
     let cssStyles = [];
 
-    for (let stylesheet of stylesheets)
-    {
+    let stylesheetOnlyChange = !!stylesheets;
+    if (!stylesheets)
+      stylesheets = this.window.document.styleSheets;
+
+    // Chrome < 51 doesn't have an iterable StyleSheetList
+    // https://issues.adblockplus.org/ticket/5381
+    for (let i = 0; i < stylesheets.length; i++)
+    {
+      let stylesheet = stylesheets[i];
       // Explicitly ignore third-party stylesheets to ensure consistent behavior
       // between Firefox and Chrome.
       if (!this.isSameOrigin(stylesheet))
         continue;
 
       let rules = stylesheet.cssRules;
       if (!rules)
         continue;
 
       for (let rule of rules)
       {
         if (rule.type != rule.STYLE_RULE)
           continue;
 
         cssStyles.push(stringifyStyle(rule));
       }
     }
 
+    let {document} = this.window;
     for (let pattern of this.patterns)
     {
+      if (stylesheetOnlyChange &&
+          !pattern.selectors.some(selector => selector.dependsOnStyles))
+      {
+        continue;
+      }
+
       for (let selector of evaluate(pattern.selectors,
                                     0, "", document, cssStyles))
       {
-        if (!pattern.selectors.some(s => s.requiresHiding))
+        if (pattern.selectors.some(s => s.preferHideWithSelector) &&
+            !pattern.selectors.some(s => s.requiresHiding))
         {
           selectors.push(selector);
           selectorFilters.push(pattern.text);
         }
         else
         {
           for (let element of document.querySelectorAll(selector))
           {
             elements.push(element);
             elementFilters.push(pattern.text);
           }
         }
       }
     }
 
     this.addSelectorsFunc(selectors, selectorFilters);
     this.hideElemsFunc(elements, elementFilters);
   },
 
+  _stylesheetQueue: null,
+
   onLoad(event)
   {
     let stylesheet = event.target.sheet;
     if (stylesheet)
-      this.addSelectors([stylesheet]);
+    {
+      if (!this._stylesheetQueue &&
+          Date.now() - this._lastInvocation < MIN_INVOCATION_INTERVAL)
+      {
+        this._stylesheetQueue = [];
+        this.window.setTimeout(() =>
+        {
+          let stylesheets = this._stylesheetQueue;
+          this._stylesheetQueue = null;
+          this.addSelectors(stylesheets);
+        }, MIN_INVOCATION_INTERVAL - (Date.now() - this._lastInvocation));
+      }
+
+      if (this._stylesheetQueue)
+        this._stylesheetQueue.push(stylesheet);
+      else
+        this.addSelectors([stylesheet]);
+    }
   },
 
   apply()
   {
     this.getFiltersFunc(patterns =>
     {
       this.patterns = [];
       for (let pattern of patterns)
       {
-        let selectors = parseSelector(pattern.selector);
+        let selectors = this.parseSelector(pattern.selector);
         if (selectors != null && selectors.length > 0)
           this.patterns.push({selectors, text: pattern.text});
       }
 
       if (this.patterns.length > 0)
       {
         let {document} = this.window;
-        this.addSelectors(document.styleSheets);
+        this.addSelectors();
         document.addEventListener("load", this.onLoad.bind(this), true);
       }
     });
   }
 };
 
-if (typeof exports != "undefined")

[kzar, 2017/06/12 12:50:13]

Don't we expect exports to always exist like for the other modules?

[hub, 2017/06/12 13:26:34]

Sadly no, we can't expect that yet.

-in the tests, this is not loaded using require() at least until we fix this.
-common.js does it for the same reason.

[kzar, 2017/06/12 13:35:12]

Ah right, well I think we need to fix that at the same time as we make this
change. See my other reply.

[hub, 2017/06/12 14:03:13]

agreed.

[kzar, 2017/07/07 13:42:20]

After reading through this review again I think removing this check and the
similar one from common.js is what still needs doing. Could you remove those,
fixing the related stuff you mentioned above?

[hub, 2017/08/10 14:46:21]

Acknowledged.

-{
-  exports.ElemHideEmulation = ElemHideEmulation;
-  exports.splitSelector = splitSelector;
-}
+exports.ElemHideEmulation = ElemHideEmulation;
+exports.splitSelector = splitSelector;

[Wladimir Palant, 2017/08/16 09:55:53]

This shouldn't export splitSelector. If we need this functionality elsewhere, it
should go into common.js or something like that.

[kzar, 2017/08/16 09:59:05]

Acknowledged, OK I'll move that over while I'm at it.