Issue 6526 - Use the maybe version of Compile() and Run()

src/JsEngine.cpp

 /*
  * 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 @@
     if (filename.length())
     {
       const v8::Local<v8::String> v8Filename = ToV8String(isolate, filename);
       v8::ScriptOrigin scriptOrigin(v8Filename);
       return v8::Script::Compile(isolate->GetCurrentContext(), v8Source, &scriptOrigin);
     }
     else
       return v8::Script::Compile(isolate->GetCurrentContext(), v8Source);
   }
 
-  /*
-   * Check that a Maybe<> isn't empty, and throw a JsValueError if it is.
-   * Call using the macro %CHECK_MAYBE to get the location.
-   */
-  template<class T>
-  void CheckMaybe(v8::Isolate* isolate, const v8::MaybeLocal<T>& value,
-                  const char* filename, int line)
-  {
-    if (value.IsEmpty())
-      throw AdblockPlus::JsError("Empty value at ", filename, line);
-  }
-
-#define CHECK_MAYBE(isolate, value) \
-  CheckMaybe(isolate, value, __FILE__, __LINE__)
-
   class V8Initializer
   {
     V8Initializer()
       : platform{nullptr}
     {
       std::string cmd = "--use_strict";
       v8::V8::SetFlagsFromString(cmd.c_str(), cmd.length());
       platform = v8::platform::CreateDefaultPlatform();
       v8::V8::InitializePlatform(platform);
       v8::V8::Initialize();
@@ skipping 125 matching lines @@
 AdblockPlus::JsValue AdblockPlus::JsEngine::GetGlobalObject()
 {
   JsContext context(*this);
   return JsValue(shared_from_this(), context.GetV8Context()->Global());
 }
 
 AdblockPlus::JsValue AdblockPlus::JsEngine::Evaluate(const std::string& source,
     const std::string& filename)
 {
   const JsContext context(*this);
-  const v8::TryCatch tryCatch(GetIsolate());
-  v8::MaybeLocal<v8::Script> script = CompileScript(GetIsolate(), source,
-    filename);
-  CHECK_MAYBE(GetIsolate(), script);
-  v8::MaybeLocal<v8::Value> result = script.ToLocalChecked()->Run(
-    GetIsolate()->GetCurrentContext());
-  CHECK_MAYBE(GetIsolate(), result);
-  return JsValue(shared_from_this(), result.ToLocalChecked());

[sergei, 2018/06/20 15:09:55]

I think it's very important to keep the exception if there were some. It helped
me several times, so I would propose to not remove the call
`CheckTryCatch(GetIsolate(), tryCatch);`.

What do you think about something like

auto script = CheckedToLocal(tryCatch, CompileScript(GetIsolate(), source,
filename);
auto result = CheckedToLocal(tryCatch,
script->Run(GetIsolate()->GetCurrentContext()));
return JsValue(shared_from_this(), CheckedToLocal(tryCatch, result));

where CheckedToLocal is perhaps a template function, we can elaborate here
later, BTW
template<typename T>
v8::Local<T> CheckedToLocal(tryCatch, value, filename, line)
{
  CheckTryCatch(GetIsolate(), tryCatch);
  if (value.IsEmpty()) // here could even use V8_UNLIKELY
    throw AdblockPlus::JsError("Empty value at ", filename, line);
  return value.ToLocalChecked();
}
(the macro with __FILE__, __LINE__ is omitted).

[hub, 2018/06/20 16:09:21]

Done.

+  auto isolate = GetIsolate();
+  const v8::TryCatch tryCatch(isolate);
+  auto script = CHECKED_TO_LOCAL(
+    isolate, CompileScript(isolate, source, filename), tryCatch);
+  auto result = CHECKED_TO_LOCAL(
+    isolate, script->Run(isolate->GetCurrentContext()), tryCatch);
+  return JsValue(shared_from_this(), result);
 }
 
 void AdblockPlus::JsEngine::SetEventCallback(const std::string& eventName,
     const AdblockPlus::JsEngine::EventCallback& callback)
 {
   if (!callback)
   {
     RemoveEventCallback(eventName);
     return;
   }
@@ skipping 130 matching lines @@
     list.push_back(JsValue(shared_from_this(), arguments[i]));
   return list;
 }
 
 void AdblockPlus::JsEngine::SetGlobalProperty(const std::string& name,
                                               const AdblockPlus::JsValue& value)
 {
   auto global = GetGlobalObject();
   global.SetProperty(name, value);
 }