Issue 6957 - Add rulesFromStyleSheet function to ElemHide module

test/elemHide.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 {createSandbox} = require("./_common");
 
 let ElemHide = null;
 let createStyleSheet = null;
+let rulesFromStyleSheet = null;
 let ElemHideExceptions = null;
 let Filter = null;
 let filtersByDomain = null;
 let selectorGroupSize = null;
 
 exports.setUp = function(callback)
 {
   let sandboxedRequire = createSandbox({
     extraExports: {
       elemHide: ["filtersByDomain", "selectorGroupSize"]
     }
   });
   (
-    {ElemHide, createStyleSheet, filtersByDomain, selectorGroupSize} =
-      sandboxedRequire("../lib/elemHide"),
+    {ElemHide, createStyleSheet, rulesFromStyleSheet,
+     filtersByDomain, selectorGroupSize} = sandboxedRequire("../lib/elemHide"),
     {ElemHideExceptions} = sandboxedRequire("../lib/elemHideExceptions"),
     {Filter} = sandboxedRequire("../lib/filterClasses")
   );
 
   callback();
 };
 
 function normalizeSelectors(selectors)
 {
   // generateStyleSheetForDomain is currently allowed to return duplicate
@@ skipping 249 matching lines @@
 
   let selectors = new Array(50000).map((element, index) => ".s" + index);
 
   test.equal((createStyleSheet(selectors).match(/\n/g) || []).length,
              Math.ceil(50000 / selectorGroupSize),
              "Style sheet should be split up into rules with at most " +
              selectorGroupSize + " selectors each");
 
   test.done();
 };
+
+exports.testRulesFromStyleSheet = function(test)
+{
+  // Note: The rulesFromStyleSheet function assumes that each rule will be
+  // terminated with a newline character, including the last rule. If this is
+  // not the case, the function goes into an infinite loop. It should only be
+  // used with the return value of the createStyleSheet function.
+
+  test.deepEqual([...rulesFromStyleSheet("")], []);
+  test.deepEqual([...rulesFromStyleSheet("#foo {}\n")], ["#foo {}"]);
+  test.deepEqual([...rulesFromStyleSheet("#foo {}\n#bar {}\n")],
+                 ["#foo {}", "#bar {}"]);
+
+  test.done();
+};