add async context versions of MakeCallback

This commit adds support for the async context accepting versions of
node::MakeCallback. An async_context concept has been added as a
wrapper around node::async_context, along with APIs for initializing
and destroying async context, similar to how [N-API][] exposes this
functionality.

Ref: nodejs/node#13254
[N-API]: https://nodejs.org/dist/latest-v9.x/docs/api/n-api.html#n_api_custom_asynchronous_operations

Makefile

@@ -52,6 +52,7 @@ LINT_SOURCES = \
 	test/cpp/json-parse.cpp \
 	test/cpp/json-stringify.cpp \
 	test/cpp/makecallback.cpp \
+	test/cpp/makecallbackcontext.cpp \
 	test/cpp/morenews.cpp \
 	test/cpp/multifile1.cpp \
 	test/cpp/multifile2.cpp \

doc/node_misc.md

@@ -1,10 +1,45 @@
 ## Miscellaneous Node Helpers
 
  - <a href="#api_nan_make_callback"><b><code>Nan::MakeCallback()</code></b></a>
+ - <a href="#api_nan_async_init"><b><code>Nan::AsyncInit()</code></b></a>
+ - <a href="#api_nan_async_destory"><b><code>Nan::AsyncDestory()</code></b></a>
  - <a href="#api_nan_module_init"><b><code>NAN_MODULE_INIT()</code></b></a>
  - <a href="#api_nan_export"><b><code>Nan::Export()</code></b></a>
 
 
+<a name="api_async_init"></a>
+### Nan::AsyncInit()
+
+When calling back into JavaScript asynchornously, special care must be taken to ensure that the runtime can properly track
+async hops. `Nan::AsyncInit` is an object that wraps `node::EmitAsyncInit` and returns a wrapper for the
+`node::async_context` structure. The `async_context` can be provided to `Nan::MakeCallback` to properly restore the correct
+async execution context.
+
+Signatures:
+
+```c++
+Nan::async_context AsyncInit(v8::MaybeLocal<v8::Object> maybe_resource,
+                             const char* name);
+Nan::async_context AsyncInit(v8::MaybeLocal<v8::Object> maybe_resource,
+                             v8::Local<v8::String> name);
+```
+
+* `maybe_resource`: An optional object associated with the async work that will be passed to the possible [async_hooks][]
+  `init` hook.
+* `name`: Identified for the kind of resource that is being provided for diagnostics information exposed by the [async_hooks][]
+  API. This will be passed to the possible `init` hook as the `type`. To avoid name collisions with other modules we recommend
+  that the name include the name of the owning module as a prefix. For example `mysql` module could use something like
+  `mysql:batch-db-query-resource`.
+* An opaque `async_context` structure is returned. This should be passed to any `Nan::MakeCallback` operations done later.
+
+For more details, see the Node [async_hooks][] documentation. You might also want to take a look at the documentation for the
+[N-API counterpart][napi]. For example usage, see the `makecallbackcontext.cpp` example in the `test/cpp` directory.
+
+<a name="api_async_destory"></a>
+### Nan::AsyncDestroy()
+
+Wrapper around `node::EmitAsyncDestroy`.
+
 <a name="api_nan_make_callback"></a>
 ### Nan::MakeCallback()
 
@@ -15,6 +50,23 @@ Use `MakeCallback()` rather than using `v8::Function#Call()` directly in order t
 Signatures:
 
 ```c++
+v8::Local<v8::Value> Nan::MakeCallback(v8::Local<v8::Object> target,
+                                       v8::Local<v8::Function> func,
+                                       int argc,
+                                       v8::Local<v8::Value>* argv,
+                                       Nan::async_context async_context);
+v8::Local<v8::Value> Nan::MakeCallback(v8::Local<v8::Object> target,
+                                       v8::Local<v8::String> symbol,
+                                       int argc,
+                                       v8::Local<v8::Value>* argv,
+                                       Nan::async_context async_context);
+v8::Local<v8::Value> Nan::MakeCallback(v8::Local<v8::Object> target,
+                                       const char* method,
+                                       int argc,
+                                       v8::Local<v8::Value>* argv,
+                                       Nan::async_context async_context);
+
+// Legacy versions. We recommend the async context preserving versions above.
 v8::Local<v8::Value> Nan::MakeCallback(v8::Local<v8::Object> target,
                                        v8::Local<v8::Function> func,
                                        int argc,
@@ -61,3 +113,6 @@ NAN_MODULE_INIT(Init) {
   NAN_EXPORT(target, Foo);
 }
 ```
+
+[async_hooks]: https://nodejs.org/dist/latest-v9.x/docs/api/async_hooks.html
+[napi]: https://nodejs.org/dist/latest-v9.x/docs/api/n-api.html#n_api_custom_asynchronous_operations

nan.h

@@ -871,6 +871,92 @@ class TryCatch {
 #endif
   }
 
+#if NODE_MODULE_VERSION >= NODE_8_0_MODULE_VERSION
+  typedef node::async_context async_context;
+#else
+  struct async_context {};
+#endif
+
+  inline async_context AsyncInit(
+      v8::MaybeLocal<v8::Object> maybe_resource
+    , v8::Local<v8::String> resource_name) {
+#if NODE_MODULE_VERSION < NODE_8_0_MODULE_VERSION
+    return async_context();
+#else
+    v8::Isolate* isolate = v8::Isolate::GetCurrent();
+
+    v8::Local<v8::Object> resource =
+        maybe_resource.IsEmpty() ? New<v8::Object>()
+                                 : maybe_resource.ToLocalChecked();
+
+    node::async_context context =
+        node::EmitAsyncInit(isolate, resource, resource_name);
+    return static_cast<async_context>(context);
+#endif
+  }
+
+  inline async_context AsyncInit(
+      v8::MaybeLocal<v8::Object> maybe_resource
+    , const char* name) {
+    return AsyncInit(maybe_resource, New<v8::String>(name).ToLocalChecked());
+  }
+
+  inline void AsyncDestroy(async_context context) {
+#if NODE_MODULE_VERSION >= NODE_8_0_MODULE_VERSION
+    v8::Isolate* isolate = v8::Isolate::GetCurrent();
+    node::async_context node_context = static_cast<node::async_context>(context);
+    node::EmitAsyncDestroy(isolate, node_context);
+#endif
+  }
+
+  inline v8::MaybeLocal<v8::Value> MakeCallback(
+      v8::Local<v8::Object> target
+    , v8::Local<v8::Function> func
+    , int argc
+    , v8::Local<v8::Value>* argv
+    , async_context asyncContext) {
+#if NODE_MODULE_VERSION < NODE_8_0_MODULE_VERSION
+    // Ignore the async_context value.
+    return MakeCallback(target, func, argc, argv);
+#else
+    return node::MakeCallback(
+        v8::Isolate::GetCurrent(), target, func, argc, argv,
+        static_cast<node::async_context>(asyncContext));
+#endif
+  }
+
+  inline v8::MaybeLocal<v8::Value> MakeCallback(
+      v8::Local<v8::Object> target
+    , v8::Local<v8::String> symbol
+    , int argc
+    , v8::Local<v8::Value>* argv
+    , async_context asyncContext) {
+#if NODE_MODULE_VERSION < NODE_8_0_MODULE_VERSION
+    // Ignore the async_context value.
+    return MakeCallback(target, symbol, argc, argv);
+#else
+    return node::MakeCallback(
+        v8::Isolate::GetCurrent(), target, symbol, argc, argv,
+        static_cast<node::async_context>(asyncContext));
+#endif
+  }
+
+  inline v8::MaybeLocal<v8::Value> MakeCallback(
+      v8::Local<v8::Object> target
+    , const char* method
+    , int argc
+    , v8::Local<v8::Value>* argv
+    , async_context asyncContext) {
+#if NODE_MODULE_VERSION < NODE_8_0_MODULE_VERSION
+    // Ignore the async_context value.
+    return MakeCallback(target, method, argc, argv);
+#else
+    return node::MakeCallback(
+        v8::Isolate::GetCurrent(), target, method, argc, argv,
+        static_cast<node::async_context>(asyncContext));
+#endif
+  }
+
   inline void FatalException(const TryCatch& try_catch) {
     node::FatalException(v8::Isolate::GetCurrent(), try_catch.try_catch_);
   }

test/binding.gyp

@@ -90,6 +90,10 @@
         "target_name" : "makecallback"
       , "sources"     : [ "cpp/makecallback.cpp" ]
     }
+    , {
+        "target_name" : "makecallbackcontext"
+      , "sources"     : [ "cpp/makecallbackcontext.cpp" ]
+    }
     , {
         "target_name" : "isolatedata"
       , "sources"     : [ "cpp/isolatedata.cpp" ]

test/cpp/makecallbackcontext.cpp

@@ -0,0 +1,65 @@
+/*********************************************************************
+ * NAN - Native Abstractions for Node.js
+ *
+ * Copyright (c) 2018 NAN contributors
+ *
+ * MIT License <https://github.com/nodejs/nan/blob/master/LICENSE.md>
+ ********************************************************************/
+
+#include <nan.h>
+#include <unistd.h>
+
+using namespace Nan;  // NOLINT(build/namespaces)
+
+class DelayRequest {
+ public:
+  DelayRequest(int milliseconds_, v8::Local<v8::Function> callback_)
+    : milliseconds(milliseconds_) {
+      callback.Reset(callback_);
+      request.data = this;
+      asyncContext = AsyncInit(v8::MaybeLocal<v8::Object>(), "test.DelayRequest");
+    }
+  ~DelayRequest() {
+    AsyncDestroy(asyncContext);
+    callback.Reset();
+  }
+
+  Persistent<v8::Function> callback;
+  uv_work_t request;
+  async_context asyncContext;
+  int milliseconds;
+};
+
+void Delay(uv_work_t* req) {
+  DelayRequest *delay_request = static_cast<DelayRequest*>(req->data);
+  sleep(delay_request->milliseconds / 1000);
+}
+
+void AfterDelay(uv_work_t* req, int status) {
+  HandleScope scope;
+
+  DelayRequest *delay_request = static_cast<DelayRequest*>(req->data);
+  v8::Local<v8::Function> callback = New(delay_request->callback);
+  v8::Local<v8::Value> argv[0] = {};
+
+  v8::Local<v8::Object> target = New<v8::Object>();
+  MakeCallback(target, callback, 0, argv, delay_request->asyncContext);
+
+  delete delay_request;
+}
+
+NAN_METHOD(Delay) {
+  int delay = To<int>(info[0]).FromJust();
+  v8::Local<v8::Function> cb = To<v8::Function>(info[1]).ToLocalChecked();
+
+  DelayRequest* delay_request = new DelayRequest(delay, cb);
+
+  uv_queue_work(uv_default_loop(), &delay_request->request, Delay, AfterDelay);
+}
+
+NAN_MODULE_INIT(Init) {
+  Set(target, New<v8::String>("delay").ToLocalChecked(),
+    GetFunction(New<v8::FunctionTemplate>(Delay)).ToLocalChecked());
+}
+
+NODE_MODULE(makecallbackcontext, Init)

test/js/makecallbackcontext-test.js

@@ -0,0 +1,70 @@
+/*********************************************************************
+ * NAN - Native Abstractions for Node.js
+ *
+ * Copyright (c) 2018 NAN contributors
+ *
+ * MIT License <https://github.com/nodejs/nan/blob/master/LICENSE.md>
+ ********************************************************************/
+
+try {
+  require('async_hooks');
+} catch (e) {
+  process.exit(0);
+}
+
+const test     = require('tap').test
+    , testRoot = require('path').resolve(__dirname, '..')
+    , delay = require('bindings')({ module_root: testRoot, bindings: 'makecallbackcontext' }).delay
+    , asyncHooks = require('async_hooks');
+
+test('makecallbackcontext', function (t) {
+  t.plan(7);
+
+  let resourceAsyncId;
+  let originalExecutionAsyncId;
+  let beforeCalled = false;
+  let afterCalled = false;
+  let destroyCalled = false;
+
+  let hooks = asyncHooks.createHook({
+    init(asyncId, type, triggerAsyncId, resource) {
+      if (type === 'test.DelayRequest') {
+        resourceAsyncId = asyncId;
+      }
+    },
+    before(asyncId) {
+      if (asyncId === resourceAsyncId) {
+        beforeCalled = true;
+      }
+    },
+    after(asyncId) {
+      if (asyncId === resourceAsyncId) {
+        afterCalled = true;
+      }
+    },
+    destroy(asyncId) {
+      if (asyncId === resourceAsyncId) {
+        destroyCalled = true;
+      }
+    }
+
+  });
+  hooks.enable();
+
+  originalExecutionAsyncId = asyncHooks.executionAsyncId();
+  delay(1000, () => {
+    t.equal(asyncHooks.executionAsyncId(), resourceAsyncId,
+            'callback should have the correct execution context');
+    t.equal(asyncHooks.triggerAsyncId(), originalExecutionAsyncId,
+            'callback should have the correct trigger context');
+    t.ok(beforeCalled, 'before should have been called');
+    t.notOk(afterCalled, 'after should not have been called yet');
+    setTimeout(() => {
+      t.ok(afterCalled, 'after should have been called');
+      t.ok(destroyCalled, 'destroy should have been called');
+      t.equal(asyncHooks.triggerAsyncId(), resourceAsyncId,
+              'setTimeout should have been triggered by the async resource');
+      hooks.disable();
+    }, 1);
+  });
+});