Issue 3594 - remove circular references JsEngine-JsValue-JsEngine

include/AdblockPlus/JsEngine.h

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2016 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 75 matching lines @@
      * Event callback function.
      */
     typedef std::function<void(JsValueList& params)> EventCallback;
 
     /**
      * Maps events to callback functions.
      */
     typedef std::map<std::string, EventCallback> EventMap;
 
     /**
+     * Exception which is thrown when JsEngine is not available.
+     *
+     * For instance, if JsEngine is already released but someone calls a method
+     * on JsValue this exception will be thrown.
+     */
+    class JsEngineNotAvailableException : public std::runtime_error
+    {
+    public:
+      JsEngineNotAvailableException()
+        : std::runtime_error("JsEngine is not available")
+      {
+      }
+    };
+
+    /**
      * Creates a new JavaScript engine instance.
      * @param appInfo Information about the app.
      * @param isolate v8::Isolate wrapper. This parameter should be considered
      *        as a temporary hack for tests, it will go away. Issue #3593.
      * @return New `JsEngine` instance.
      */
     static JsEnginePtr New(const AppInfo& appInfo = AppInfo(), const ScopedV8IsolatePtr& isolate = ScopedV8IsolatePtr(new ScopedV8Isolate()));
 
     /**
      * Registers the callback function for an event.
@@ skipping 154 matching lines @@
     FileSystemPtr fileSystem;
     WebRequestPtr webRequest;
     LogSystemPtr logSystem;
     std::unique_ptr<v8::Persistent<v8::Context>> context;
     EventMap eventCallbacks;
     JsValuePtr globalJsObject;
   };
 }
 
 #endif