Issue 6847 - Add regular expression support to snippets

lib/content/snippets.js

Index: lib/content/snippets.js
===================================================================
--- a/lib/content/snippets.js
+++ b/lib/content/snippets.js
@@ -16,16 +16,50 @@
  */
 
 /* eslint-env webextensions */
 /* eslint no-console: "off" */
 
 "use strict";
 
 /**
+ * Escapes regular expression special characters in a string. The returned
+ * string may be passed to the <code>RegExp</code> constructor to match the
+ * original string.
+ *
+ * @param {string} string The string in which to escape special characters.
+ *
+ * @returns {string} A new string with the special characters escaped.
+ */
+function regexEscape(string)
+{
+  return string.replace(/[-/\\^$*+?.()|[\]{}]/g, "\\$&");
+}
+
+/**
+ * Converts a given pattern to a regular expression.
+ *
+ * @param {string} pattern The pattern to convert. If the pattern begins and
+ * ends with a slash (<code>/</code>), the text in between is treated as a
+ * regular expression; otherwise the pattern is treated as raw text.
+ *
+ * @returns {RegExp} A <code>RegExp</code> object based on the given pattern.
+ */
+function toRegExp(pattern)
+{
+  if (pattern.length >= 2 && pattern[0] == "/" &&
+      pattern[pattern.length - 1] == "/")
+  {
+    return new RegExp(pattern.substring(1, pattern.length - 1));
+  }
+
+  return new RegExp(regexEscape(pattern));
+}
+
+/**
  * Injects JavaScript code into the document using a temporary
  * <code>script</code> element.
  *
  * @param {string} code The code to inject.
  * @param {Array.<function|string>} [dependencies] A list of dependencies
  *   to inject along with the code. A dependency may be either a function or a
  *   string containing some executable code.
  */
@@ -181,46 +215,49 @@
 
 exports["uabinject-defuser"] = makeInjector(uabinjectDefuser);
 
 /**
  * Hides any HTML element or one of its ancestors matching a CSS selector if
  * the text content of the element's shadow contains a given string.
  *
  * @param {string} search The string to look for in every HTML element's
- *   shadow.
+ *   shadow. If the string begins and ends with a slash (<code>/</code>), the
+ *   text in between is treated as a regular expression.
  * @param {string} selector The CSS selector that an HTML element must match
  *   for it to be hidden.
  */
 function hideIfShadowContains(search, selector = "*")
 {
   let originalAttachShadow = Element.prototype.attachShadow;
 
   // If there's no Element.attachShadow API present then we don't care, it must
   // be Firefox or an older version of Chrome.
   if (!originalAttachShadow)
     return;
 
+  let re = toRegExp(search);
+
   // Mutation observers mapped to their corresponding shadow roots and their
   // hosts.
   let shadows = new WeakMap();
 
   function observeShadow(mutations, observer)
   {
     let {host, root} = shadows.get(observer) || {};
 
     // Since it's a weak map, it's possible that either the element or its
     // shadow has been removed.
     if (!host || !root)
       return;
 
     // If the shadow contains the given text, check if the host or one of its
     // ancestors matches the selector; if a matching element is found, hide
     // it.
-    if (root.textContent.includes(search))
+    if (re.test(root.textContent))
     {
       let closest = host.closest(selector);
       if (closest)
         hideElement(closest);
     }
   }
 
   Object.defineProperty(Element.prototype, "attachShadow", {
@@ -245,39 +282,44 @@
       shadows.set(observer, {host: this, root});
 
       return root;
     }
   });
 }
 
 exports["hide-if-shadow-contains"] = makeInjector(hideIfShadowContains,
+                                                  toRegExp, regexEscape,
                                                   hideElement);
 
 /**
  * Hides any HTML element or one of its ancestors matching a CSS selector if
  * the text content of the element contains a given string.
  *
- * @param {string} search The string to look for in HTML elements.
+ * @param {string} search The string to look for in HTML elements. If the
+ *   string begins and ends with a slash (<code>/</code>), the text in between
+ *   is treated as a regular expression.
  * @param {string} selector The CSS selector that an HTML element must match
  *   for it to be hidden.
  * @param {string?} [searchSelector] The CSS selector that an HTML element
  *   containing the given string must match. Defaults to the value of the
  *   <code>selector</code> argument.
  */
 function hideIfContains(search, selector = "*", searchSelector = null)
 {
   if (searchSelector == null)
     searchSelector = selector;
 
+  let re = toRegExp(search);
+
   new MutationObserver(() =>
   {
     for (let element of document.querySelectorAll(searchSelector))
     {
-      if (element.textContent.includes(search))
+      if (re.test(element.textContent))
       {
         let closest = element.closest(selector);
         if (closest)
           hideElement(closest);
       }
     }
   })
   .observe(document, {childList: true, characterData: true, subtree: true});