async_wrap: add uid to all asyncWrap hooks

By doing this users can use a Map object for storing information instead
of modifying the handle object.

PR-URL: https://github.com/nodejs/node/pull/4600
Reviewed-By: Trevor Norris <trev.norris@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>

src/async-wrap.cc

@@ -179,6 +179,7 @@ Local<Value> AsyncWrap::MakeCallback(const Local<Function> cb,
 
   Local<Function> pre_fn = env()->async_hooks_pre_function();
   Local<Function> post_fn = env()->async_hooks_post_function();
+  Local<Value> uid = Integer::New(env()->isolate(), get_uid());
   Local<Object> context = object();
   Local<Object> process = env()->process_object();
   Local<Object> domain;
@@ -207,14 +208,14 @@ Local<Value> AsyncWrap::MakeCallback(const Local<Function> cb,
   }
 
   if (ran_init_callback() && !pre_fn.IsEmpty()) {
-    if (pre_fn->Call(context, 0, nullptr).IsEmpty())
+    if (pre_fn->Call(context, 1, &uid).IsEmpty())
       FatalError("node::AsyncWrap::MakeCallback", "pre hook threw");
   }
 
   Local<Value> ret = cb->Call(context, argc, argv);
 
   if (ran_init_callback() && !post_fn.IsEmpty()) {
-    if (post_fn->Call(context, 0, nullptr).IsEmpty())
+    if (post_fn->Call(context, 1, &uid).IsEmpty())
       FatalError("node::AsyncWrap::MakeCallback", "post hook threw");
   }
 

test/parallel/test-async-wrap-uid.js

@@ -0,0 +1,57 @@
+'use strict';
+
+require('../common');
+const fs = require('fs');
+const assert = require('assert');
+const async_wrap = process.binding('async_wrap');
+
+const storage = new Map();
+async_wrap.setupHooks(init, pre, post, destroy);
+async_wrap.enable();
+
+function init(provider, uid) {
+  storage.set(uid, {
+    init: true,
+    pre: false,
+    post: false,
+    destroy: false
+  });
+}
+
+function pre(uid) {
+  storage.get(uid).pre = true;
+}
+
+function post(uid) {
+  storage.get(uid).post = true;
+}
+
+function destroy(uid) {
+  storage.get(uid).destroy = true;
+}
+
+fs.access(__filename, function(err) {
+  assert.ifError(err);
+});
+
+fs.access(__filename, function(err) {
+  assert.ifError(err);
+});
+
+async_wrap.disable();
+
+process.once('exit', function() {
+  assert.strictEqual(storage.size, 2);
+
+  for (const item of storage) {
+    const uid = item[0];
+    const value = item[1];
+    assert.strictEqual(typeof uid, 'number');
+    assert.deepStrictEqual(value, {
+      init: true,
+      pre: true,
+      post: true,
+      destroy: true
+    });
+  }
+});