Issue 6862 - Make Snippets module emit events

lib/snippets.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
@@ skipping 22 matching lines @@
 /**
  * Container for snippet filters
  * @class
  */
 let Snippets = Object.assign(new EventEmitter(), {
   /**
    * Removes all known filters
    */
   clear()
   {
+    if (filters.size == 0)
+      return;
+
     filters.clear();
 
     this.emit("snippets.filtersCleared");
   },
 
   /**
    * Add a new snippet filter
    * @param {SnippetFilter} filter
    */
   add(filter)
   {
+    let {size} = filters;
+
     filters.add(filter.text);
 
-    this.emit("snippets.filterAdded", filter);
+    if (size != filters.size)
+      this.emit("snippets.filterAdded", filter);
   },
 
   /**
    * Removes a snippet filter
    * @param {SnippetFilter} filter
    */
   remove(filter)
   {
+    let {size} = filters;
+
     filters.delete(filter.text);
 
-    this.emit("snippets.filterRemoved", filter);
+    if (size != filters.size)
+      this.emit("snippets.filterRemoved", filter);
   },
 
   /**
    * Returns a list of all scripts active on a particular domain
    * @param {string} domain
    * @return {string[]}
    */
   getScriptsForDomain(domain)
   {
     let result = [];
@@ skipping 117 matching lines @@
           let value = imports[name];
           if (typeof value == "function")
             value(...args);
         }
       }
     }
   `;
 }
 
 exports.compileScript = compileScript;