Issue #3593, #1197- fix isolate management

include/AdblockPlus/JsEngine.h

Index: include/AdblockPlus/JsEngine.h
diff --git a/include/AdblockPlus/JsEngine.h b/include/AdblockPlus/JsEngine.h
index bf68c378d56e4e0dcc295e488c4502950dfce7a0..8d0b5dbe438b03335b45219aa42688df5b8ac2d1 100644
--- a/include/AdblockPlus/JsEngine.h
+++ b/include/AdblockPlus/JsEngine.h
@@ -49,6 +49,31 @@ namespace AdblockPlus
   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>
@@ -72,7 +97,7 @@ namespace AdblockPlus
      * @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.
@@ -215,13 +240,24 @@ namespace AdblockPlus
      */
     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;