Issue #3593, #1197- fix isolate management

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 31 matching lines @@
 namespace AdblockPlus
 {
   class JsEngine;
 
   /**
    * Shared smart pointer to a `JsEngine` instance.
    */
   typedef std::shared_ptr<JsEngine> JsEnginePtr;
 
   /**
+   * Scope based isolate manager. Creates a new isolate instance on
+   * constructing and disposes it on destructing.
+   */
+  class ScopedV8Isolate
+  {
+  public:
+    ScopedV8Isolate();
+    ~ScopedV8Isolate();
+    v8::Isolate* Get()
+    {
+      return isolate;
+    }
+  private:
+    ScopedV8Isolate(const ScopedV8Isolate&);
+    ScopedV8Isolate& operator=(const ScopedV8Isolate&);
+
+    v8::Isolate* isolate;
+  };
+
+  /**
+   * Shared smart pointer to ScopedV8Isolate instance;
+   */
+  typedef std::shared_ptr<ScopedV8Isolate> ScopedV8IsolatePtr;
+
+  /**
    * JavaScript engine used by `FilterEngine`, wraps v8.
    */
   class JsEngine : public std::enable_shared_from_this<JsEngine>
   {
     friend class JsValue;
     friend class JsContext;
 
   public:
     /**
      * Event callback function.
      */
     typedef std::function<void(JsValueList& params)> EventCallback;
 
     /**
      * Maps events to callback functions.
      */
     typedef std::map<std::string, EventCallback> EventMap;
 
     /**
      * Creates a new JavaScript engine instance.
      * @param appInfo Information about the app.
      * @return New `JsEngine` instance.
      */
-    static JsEnginePtr New(const AppInfo& appInfo = AppInfo());
+    static JsEnginePtr New(const AppInfo& appInfo = AppInfo(), const ScopedV8IsolatePtr& isolate = ScopedV8IsolatePtr());
 
     /**
      * Registers the callback function for an event.
      * @param eventName Event name. Note that this can be any string - it's a
      *        general purpose event handling mechanism.
      * @param callback Event callback function.
      */
     void SetEventCallback(const std::string& eventName, EventCallback callback);
 
     /**
@@ skipping 122 matching lines @@
      */
     void SetLogSystem(LogSystemPtr val);
 
     /**
      * Sets a global property that can be accessed by all the scripts.
      * @param name Name of the property to set.
      * @param value Value of the property to set.
      */
     void SetGlobalProperty(const std::string& name, AdblockPlus::JsValuePtr value);
 
+    /**
+     * Returns a pointer to associated v8::Isolate.
+     */
+    v8::Isolate* GetIsolate()
+    {
+      return isolate->Get();
+    }
+
   private:
-    JsEngine();
+    explicit JsEngine(const ScopedV8IsolatePtr& isolate);
+
+    /// Isolate must be disposed only after disposing of all objects which are
+    /// using it.
+    ScopedV8IsolatePtr isolate;

[Eric, 2016/01/27 17:21:02]

You should be able to declare this member 'const'. Doing that may cause some
slight trouble with initialization, but getting to this declaration is a sign of
a clean design.

[sergei, 2016/01/28 14:02:50]

I don't think that it would be better here. I would like to have a transparent
const-correctness. `const` before smart pointer type is rather error-prone
because it can be accidentally wrongly interpreted as a const pointer, which is
wrong, we still can call non-const methods of this pointer. In addition I think
that a const method returning non-const pointer or reference is rather
dangerous, of course there are exception, but here it's not that case.

[Eric, 2016/01/28 16:42:41]

I've said before that this member should _not_ be a smart pointer. The smart
pointer should be inside another class.

[sergei, 2016/01/29 11:31:14]

I have just explained my point of view regarding using `const` before smart
pointers. What concerns the smart pointer, I don't think we need any of them
here.
It's discussed here
https://codereview.adblockplus.org/6233220328718336/diff/29334316/include/Adb...

On 2016/01/27 15:06:08, sergei wrote:

[Eric, 2016/02/09 14:59:14]

I am seriously beginning to think you don't actually read what I say with any
degree of care, because you're arguing against a straw man here. That's _not_
what I was suggesting.

 
     FileSystemPtr fileSystem;
     WebRequestPtr webRequest;
     LogSystemPtr logSystem;
-    v8::Isolate* isolate;
     std::unique_ptr<v8::Persistent<v8::Context>> context;
     EventMap eventCallbacks;
     JsValuePtr globalJsObject;
   };
 }
 
 #endif