Issue 5183 - Provide async interface for FileSystem

src/FileSystemJsObject.cpp

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2017 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
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 #include <AdblockPlus/FileSystem.h>
 #include <stdexcept>
 #include <sstream>
 #include <vector>
 
 #include <AdblockPlus/JsValue.h>
 #include "FileSystemJsObject.h"
 #include "JsContext.h"
 #include "Utils.h"
 
 using namespace AdblockPlus;
+using AdblockPlus::Utils::ThrowExceptionInJS;
 
 namespace
 {
-  v8::Handle<v8::Value> ReadCallback(const v8::Arguments& arguments)
+  void ReadCallback(const v8::FunctionCallbackInfo<v8::Value>& arguments)
   {
     AdblockPlus::JsEnginePtr jsEngine = AdblockPlus::JsEngine::FromArguments(arguments);
     AdblockPlus::JsValueList converted = jsEngine->ConvertArguments(arguments);
 
     v8::Isolate* isolate = arguments.GetIsolate();
     if (converted.size() != 2)
-      return v8::ThrowException(Utils::ToV8String(isolate,
-        "_fileSystem.read requires 2 parameters"));
+      return ThrowExceptionInJS(isolate, "_fileSystem.read requires 2 parameters");
     if (!converted[1].IsFunction())
-      return v8::ThrowException(Utils::ToV8String(isolate,
-        "Second argument to _fileSystem.read must be a function"));
-
-
-    JsValue callback(converted[1]);
-    jsEngine->GetFileSystem()->Read(converted[0].AsString(),
-      [jsEngine, callback]

[sergei, 2017/06/16 15:05:55]

Here and below that's what we also want to avoid. Currently FileSystem is held
by JsEngine and storing of either std::shared_ptr<JsEngine> or JsValue in the
closure here creates a circular reference. Instead std::weak_ptr<JsEngine> and
paramsID (auto paramsID = jsEngine->StoreJsValues(converted);) should be
captured.
Like here,
https://github.com/adblockplus/libadblockplus/blob/master/src/WebRequestJsObj...

[hub, 2017/06/16 21:52:54]

Done.

-      (std::string&& content, const std::string& error)
-      {
+      return ThrowExceptionInJS(isolate, "Second argument to _fileSystem.read must be a function");
+
+    JsValueList values;
+    values.push_back(converted[1]);
+    auto weakCallback = jsEngine->StoreJsValues(values);
+    std::weak_ptr<JsEngine> weakJsEngine = jsEngine;
+    jsEngine->GetAsyncFileSystem()->Read(converted[0].AsString(),
+      [weakJsEngine, weakCallback]
+      (IFileSystem::IOBuffer&& content, const std::string& error)
+      {
+        auto jsEngine = weakJsEngine.lock();
+        if (!jsEngine)
+          return;
+
         const JsContext context(*jsEngine);
         auto result = jsEngine->NewObject();
-        result.SetProperty("content", content);

[sergei, 2017/06/16 15:05:55]

`content` should be moved, but getting into account std::vector, I guess, it
will be copied for present anyway.

[hub, 2017/06/16 21:52:54]

Acknowledged.

-        result.SetProperty("error", error);
-        JsValueList params;
-        params.push_back(result);
-        callback.Call(params);

[sergei, 2017/06/16 15:05:55]

We can simply call `callback.Call(result);` without `params`.

[hub, 2017/06/16 21:52:54]

Done.

-      });
-
-    return v8::Undefined();
-  }
-
-  v8::Handle<v8::Value> WriteCallback(const v8::Arguments& arguments)
+        result.SetStringBufferProperty("content", std::move(content));
+        if (!error.empty())
+          result.SetProperty("error", error);
+        jsEngine->TakeJsValues(weakCallback)[0].Call(result);
+      });
+  }
+
+  void WriteCallback(const v8::FunctionCallbackInfo<v8::Value>& arguments)
   {
     AdblockPlus::JsEnginePtr jsEngine = AdblockPlus::JsEngine::FromArguments(arguments);
     AdblockPlus::JsValueList converted = jsEngine->ConvertArguments(arguments);
 
     v8::Isolate* isolate = arguments.GetIsolate();
     if (converted.size() != 3)
-      return v8::ThrowException(Utils::ToV8String(isolate,
-        "_fileSystem.write requires 3 parameters"));
+      return ThrowExceptionInJS(isolate, "_fileSystem.write requires 3 parameters");
     if (!converted[2].IsFunction())
-      return v8::ThrowException(Utils::ToV8String(isolate,
-        "Third argument to _fileSystem.write must be a function"));
-
-    JsValue callback(converted[2]);
-    auto stream = std::make_shared<std::stringstream>();
-    *stream << converted[1].AsString();
-    jsEngine->GetFileSystem()->Write(converted[0].AsString(), stream,
-      [jsEngine, callback](const std::string& error)
-      {
-        const JsContext context(*jsEngine);
-        auto errorValue = jsEngine->NewValue(error);
-        JsValueList params;
-        params.push_back(errorValue);

[sergei, 2017/06/16 15:05:55]

If the error is an empty string it will be still empty string in JS and `!""` is
`true`, so I think that JS will recognize it as an error with an empty
description. I think that in case of absence of an error we should not pass
error parameter to JS, so it will be `undefined`.

BTW, I find the conversion of an empty string to nothing in C++ a bit bad, but
maybe it's OK here, since it's pretty internal thing and is documented in the
C++ interface IFileSystem.

[hub, 2017/06/16 21:52:54]

We can rework this later I think. Currently the FileSystemJsObjectTest.Write
test assume error to be "" if none.

-        callback.Call(params);
-      });
-
-    return v8::Undefined();
-  }
-
-  v8::Handle<v8::Value> MoveCallback(const v8::Arguments& arguments)
+      return ThrowExceptionInJS(isolate, "Third argument to _fileSystem.write must be a function");
+
+    JsValueList values;
+    values.push_back(converted[2]);
+    auto weakCallback = jsEngine->StoreJsValues(values);
+    std::weak_ptr<JsEngine> weakJsEngine = jsEngine;
+    auto content = converted[1].AsStringBuffer();
+    jsEngine->GetAsyncFileSystem()->Write(converted[0].AsString(),
+      content,
+      [weakJsEngine, weakCallback](const std::string& error)
+      {
+        auto jsEngine = weakJsEngine.lock();
+        if (!jsEngine)
+          return;
+
+        const JsContext context(*jsEngine);
+        JsValueList params;
+        if (!error.empty())
+          params.push_back(jsEngine->NewValue(error));
+        jsEngine->TakeJsValues(weakCallback)[0].Call(params);
+      });
+  }
+
+  void MoveCallback(const v8::FunctionCallbackInfo<v8::Value>& arguments)
   {
     AdblockPlus::JsEnginePtr jsEngine = AdblockPlus::JsEngine::FromArguments(arguments);
     AdblockPlus::JsValueList converted = jsEngine->ConvertArguments(arguments);
 
     v8::Isolate* isolate = arguments.GetIsolate();
     if (converted.size() != 3)
-      return v8::ThrowException(Utils::ToV8String(isolate,
-        "_fileSystem.move requires 3 parameters"));
+      return ThrowExceptionInJS(isolate, "_fileSystem.move requires 3 parameters");
     if (!converted[2].IsFunction())
-      return v8::ThrowException(Utils::ToV8String(isolate,
-        "Third argument to _fileSystem.move must be a function"));
-
-    JsValue callback(converted[2]);
-    jsEngine->GetFileSystem()->Move(converted[0].AsString(),
+      return ThrowExceptionInJS(isolate, "Third argument to _fileSystem.move must be a function");
+
+    JsValueList values;
+    values.push_back(converted[2]);
+    auto weakCallback = jsEngine->StoreJsValues(values);
+    std::weak_ptr<JsEngine> weakJsEngine = jsEngine;
+    jsEngine->GetAsyncFileSystem()->Move(converted[0].AsString(),
       converted[1].AsString(),
-      [jsEngine, callback](const std::string& error)
-      {
-        const JsContext context(*jsEngine);
-        auto errorValue = jsEngine->NewValue(error);
-        JsValueList params;
-        params.push_back(errorValue);
-        callback.Call(params);
-      });
-
-    return v8::Undefined();
-  }
-
-  v8::Handle<v8::Value> RemoveCallback(const v8::Arguments& arguments)
+      [weakJsEngine, weakCallback](const std::string& error)
+      {
+        auto jsEngine = weakJsEngine.lock();
+        if (!jsEngine)
+          return;
+
+        const JsContext context(*jsEngine);
+        JsValueList params;
+        if (!error.empty())
+          params.push_back(jsEngine->NewValue(error));
+        jsEngine->TakeJsValues(weakCallback)[0].Call(params);
+      });
+  }
+
+  void RemoveCallback(const v8::FunctionCallbackInfo<v8::Value>& arguments)
   {
     AdblockPlus::JsEnginePtr jsEngine = AdblockPlus::JsEngine::FromArguments(arguments);
     AdblockPlus::JsValueList converted = jsEngine->ConvertArguments(arguments);
 
     v8::Isolate* isolate = arguments.GetIsolate();
     if (converted.size() != 2)
-      return v8::ThrowException(Utils::ToV8String(isolate,
-        "_fileSystem.remove requires 2 parameters"));
+      return ThrowExceptionInJS(isolate, "_fileSystem.remove requires 2 parameters");
     if (!converted[1].IsFunction())
-      return v8::ThrowException(Utils::ToV8String(isolate,
-        "Second argument to _fileSystem.remove must be a function"));
-
-    JsValue callback(converted[1]);
-    jsEngine->GetFileSystem()->Remove(converted[0].AsString(),
-      [jsEngine, callback](const std::string& error)
-      {
-        const JsContext context(*jsEngine);
-        auto errorValue = jsEngine->NewValue(error);
-        JsValueList params;
-        params.push_back(errorValue);
-        callback.Call(params);
-      });
-
-    return v8::Undefined();
-  }
-
-  v8::Handle<v8::Value> StatCallback(const v8::Arguments& arguments)
+      return ThrowExceptionInJS(isolate, "Second argument to _fileSystem.remove must be a function");
+
+    JsValueList values;
+    values.push_back(converted[1]);
+    auto weakCallback = jsEngine->StoreJsValues(values);
+    std::weak_ptr<JsEngine> weakJsEngine = jsEngine;
+    jsEngine->GetAsyncFileSystem()->Remove(converted[0].AsString(),
+      [weakJsEngine, weakCallback](const std::string& error)
+      {
+        auto jsEngine = weakJsEngine.lock();
+        if (!jsEngine)
+          return;
+
+        const JsContext context(*jsEngine);
+        JsValueList params;
+        if (!error.empty())
+          params.push_back(jsEngine->NewValue(error));
+        jsEngine->TakeJsValues(weakCallback)[0].Call(params);
+      });
+  }
+
+  void StatCallback(const v8::FunctionCallbackInfo<v8::Value>& arguments)
   {
     AdblockPlus::JsEnginePtr jsEngine = AdblockPlus::JsEngine::FromArguments(arguments);
     AdblockPlus::JsValueList converted = jsEngine->ConvertArguments(arguments);
 
     v8::Isolate* isolate = arguments.GetIsolate();
     if (converted.size() != 2)
-      return v8::ThrowException(Utils::ToV8String(isolate,
-        "_fileSystem.stat requires 2 parameters"));
+      return ThrowExceptionInJS(isolate, "_fileSystem.stat requires 2 parameters");
     if (!converted[1].IsFunction())
-      return v8::ThrowException(Utils::ToV8String(isolate,
-        "Second argument to _fileSystem.stat must be a function"));
-
-    JsValue callback(converted[1]);
-    jsEngine->GetFileSystem()->Stat(converted[0].AsString(),
-      [jsEngine, callback]
+      return ThrowExceptionInJS(isolate, "Second argument to _fileSystem.stat must be a function");
+
+    JsValueList values;
+    values.push_back(converted[1]);
+    auto weakCallback = jsEngine->StoreJsValues(values);
+    std::weak_ptr<JsEngine> weakJsEngine = jsEngine;
+    jsEngine->GetAsyncFileSystem()->Stat(converted[0].AsString(),
+      [weakJsEngine, weakCallback]
       (const IFileSystem::StatResult& statResult, const std::string& error)
       {
+        auto jsEngine = weakJsEngine.lock();
+        if (!jsEngine)
+          return;
+
         const JsContext context(*jsEngine);
         auto result = jsEngine->NewObject();
 
         result.SetProperty("exists", statResult.exists);
         result.SetProperty("isFile", statResult.isFile);
         result.SetProperty("isDirectory", statResult.isDirectory);
         result.SetProperty("lastModified", statResult.lastModified);
-        result.SetProperty("error", error);
+        if (!error.empty())
+          result.SetProperty("error", error);
 
         JsValueList params;
         params.push_back(result);
-        callback.Call(params);
-      });
-
-    return v8::Undefined();
-  }
-
-  v8::Handle<v8::Value> ResolveCallback(const v8::Arguments& arguments)
+        jsEngine->TakeJsValues(weakCallback)[0].Call(params);
+      });
+  }
+
+  void ResolveCallback(const v8::FunctionCallbackInfo<v8::Value>& arguments)
   {
     AdblockPlus::JsEnginePtr jsEngine = AdblockPlus::JsEngine::FromArguments(arguments);
     AdblockPlus::JsValueList converted = jsEngine->ConvertArguments(arguments);
 
     v8::Isolate* isolate = arguments.GetIsolate();
     if (converted.size() != 1)
-      return v8::ThrowException(Utils::ToV8String(isolate,
-        "_fileSystem.resolve requires 1 parameter"));
-
-    std::string resolved = jsEngine->GetFileSystem()->Resolve(converted[0].AsString());
-
-    return Utils::ToV8String(isolate, resolved);
-  }
-
+      return ThrowExceptionInJS(isolate, "_fileSystem.resolve requires 1 parameter");
+
+    std::string resolved = jsEngine->GetAsyncFileSystem()->Resolve(converted[0].AsString());
+    arguments.GetReturnValue().Set(Utils::ToV8String(isolate, resolved));
+  }
 }
 
 
 JsValue& FileSystemJsObject::Setup(JsEngine& jsEngine, JsValue& obj)
 {
   obj.SetProperty("read", jsEngine.NewCallback(::ReadCallback));
   obj.SetProperty("write", jsEngine.NewCallback(::WriteCallback));
   obj.SetProperty("move", jsEngine.NewCallback(::MoveCallback));
   obj.SetProperty("remove", jsEngine.NewCallback(::RemoveCallback));
   obj.SetProperty("stat", jsEngine.NewCallback(::StatCallback));
   obj.SetProperty("resolve", jsEngine.NewCallback(::ResolveCallback));
   return obj;
 }