fix: propagate async context

This is an alternative to some of the fixes in [1].

Starting with Nan 2.9.0, we have the ability to propagate async context
across async hops. Certain variants of Nan::Callback::Call are now
deprecated to encourage use of the context presevering alternatives.
Certain variants of Node's MakeCallback that were used internally are
going to be deprecated in Node 10.

Summary is that one should use Nan::Call for sync calls, and
Nan::Callback::Call for async. The latter expects an async resource
corresponding to the async operation to be provided at the call time.

This patch fixes things up so that 1) node-sass isn't using any
deprecated APIs, and 2) properly propagates async context for async
callbacks by creating async resources in the appropriate places.

[1]: https://github.com/sass/node-sass/pull/2295

src/binding.cpp

@@ -227,9 +227,16 @@ int GetResult(sass_context_wrapper* ctx_w, Sass_Context* ctx, bool is_sync = fal
   return status;
 }
 
+void PerformCall(sass_context_wrapper* ctx_w, Nan::Callback* callback, int argc, v8::Local<v8::Value> argv[]) {
+  if (ctx_w->is_sync) {
+    Nan::Call(*callback, argc, argv);
+  } else {
+    callback->Call(argc, argv, ctx_w->async_resource);
+  }
+}
+
 void MakeCallback(uv_work_t* req) {
   Nan::HandleScope scope;
-  Nan::AsyncResource async("sass:MakeCallback");
 
   Nan::TryCatch try_catch;
   sass_context_wrapper* ctx_w = static_cast<sass_context_wrapper*>(req->data);
@@ -246,7 +253,7 @@ void MakeCallback(uv_work_t* req) {
 
   if (status == 0 && ctx_w->success_callback) {
     // if no error, do callback(null, result)
-    ctx_w->success_callback->Call(0, 0, &async);
+    PerformCall(ctx_w, ctx_w->success_callback, 0, 0);
   }
   else if (ctx_w->error_callback) {
     // if error, do callback(error)
@@ -254,7 +261,7 @@ void MakeCallback(uv_work_t* req) {
     v8::Local<v8::Value> argv[] = {
       Nan::New<v8::String>(err).ToLocalChecked()
     };
-    ctx_w->error_callback->Call(1, argv, &async);
+    PerformCall(ctx_w, ctx_w->error_callback, 1, argv);
   }
   if (try_catch.HasCaught()) {
     Nan::FatalException(try_catch);
@@ -270,6 +277,8 @@ NAN_METHOD(render) {
   struct Sass_Data_Context* dctx = sass_make_data_context(source_string);
   sass_context_wrapper* ctx_w = sass_make_context_wrapper();
 
+  ctx_w->async_resource = new Nan::AsyncResource("node-sass:sass_context_wrapper:render");
+
   if (ExtractOptions(options, dctx, ctx_w, false, false) >= 0) {
 
     int status = uv_queue_work(uv_default_loop(), &ctx_w->request, compile_it, (uv_after_work_cb)MakeCallback);
@@ -304,6 +313,8 @@ NAN_METHOD(render_file) {
   struct Sass_File_Context* fctx = sass_make_file_context(input_path);
   sass_context_wrapper* ctx_w = sass_make_context_wrapper();
 
+  ctx_w->async_resource = new Nan::AsyncResource("node-sass:sass_context_wrapper:render_file");
+
   if (ExtractOptions(options, fctx, ctx_w, true, false) >= 0) {
 
     int status = uv_queue_work(uv_default_loop(), &ctx_w->request, compile_it, (uv_after_work_cb)MakeCallback);

src/callback_bridge.h

@@ -40,6 +40,7 @@ class CallbackBridge {
     virtual std::vector<v8::Local<v8::Value>> pre_process_args(std::vector<L>) const =0;
 
     Nan::Callback* callback;
+    Nan::AsyncResource* async_resource;
     bool is_sync;
 
     uv_mutex_t cv_mutex;
@@ -66,6 +67,7 @@ CallbackBridge<T, L>::CallbackBridge(v8::Local<v8::Function> callback, bool is_s
     this->async = new uv_async_t;
     this->async->data = (void*) this;
     uv_async_init(uv_default_loop(), this->async, (uv_async_cb) dispatched_async_uv_callback);
+    this->async_resource = new Nan::AsyncResource("node-sass:CallbackBridge");
   }
 
   v8::Local<v8::Function> func = CallbackBridge<T, L>::get_wrapper_constructor().ToLocalChecked();
@@ -82,6 +84,7 @@ CallbackBridge<T, L>::~CallbackBridge() {
 
   if (!is_sync) {
     uv_close((uv_handle_t*)this->async, &async_gone);
+    delete this->async_resource;
   }
 }
 
@@ -107,7 +110,7 @@ T CallbackBridge<T, L>::operator()(std::vector<void*> argv) {
     argv_v8.push_back(Nan::New(wrapper));
 
     return this->post_process_return_value(
-      Nan::Call(*callback, argv_v8.size(), &argv_v8[0]).ToLocalChecked()
+      Nan::Call(*this->callback, argv_v8.size(), &argv_v8[0]).ToLocalChecked()
     );
   } else {
     /*
@@ -151,7 +154,6 @@ void CallbackBridge<T, L>::dispatched_async_uv_callback(uv_async_t *req) {
    * post_process_args().
    */
   Nan::HandleScope scope;
-  Nan::AsyncResource async("sass:CallbackBridge");
   Nan::TryCatch try_catch;
 
   std::vector<v8::Local<v8::Value>> argv_v8 = bridge->pre_process_args(bridge->argv);
@@ -160,7 +162,7 @@ void CallbackBridge<T, L>::dispatched_async_uv_callback(uv_async_t *req) {
   }
   argv_v8.push_back(Nan::New(bridge->wrapper));
 
-  bridge->callback->Call(argv_v8.size(), &argv_v8[0], &async);
+  bridge->callback->Call(argv_v8.size(), &argv_v8[0], bridge->async_resource);
 
   if (try_catch.HasCaught()) {
     Nan::FatalException(try_catch);

src/sass_context_wrapper.cpp

@@ -33,6 +33,9 @@ extern "C" {
     else if (ctx_w->fctx) {
       sass_delete_file_context(ctx_w->fctx);
     }
+    if (ctx_w->async_resource) {
+      delete ctx_w->async_resource;
+    }
 
     delete ctx_w->error_callback;
     delete ctx_w->success_callback;

src/sass_context_wrapper.h

@@ -39,6 +39,7 @@ extern "C" {
 
     // v8 and nan related
     Nan::Persistent<v8::Object> result;
+    Nan::AsyncResource* async_resource;
     Nan::Callback* error_callback;
     Nan::Callback* success_callback;