async_wrap: notify post if intercepted exception

The second argument of the post callback is a boolean indicating whether
the callback threw and was intercepted by uncaughtException or a domain.

Currently node::MakeCallback has no way of retrieving a uid for the
object. This is coming in a future patch.

PR-URL: https://github.com/nodejs/node/pull/5756
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Andreas Madsen <amwebdk@gmail.com>

src/async-wrap.cc

@@ -9,6 +9,7 @@
 #include "v8-profiler.h"
 
 using v8::Array;
+using v8::Boolean;
 using v8::Context;
 using v8::Function;
 using v8::FunctionCallbackInfo;
@@ -231,7 +232,9 @@ Local<Value> AsyncWrap::MakeCallback(const Local<Function> cb,
   Local<Value> ret = cb->Call(context, argc, argv);
 
   if (ran_init_callback() && !post_fn.IsEmpty()) {
-    if (post_fn->Call(context, 1, &uid).IsEmpty())
+    Local<Value> did_throw = Boolean::New(env()->isolate(), ret.IsEmpty());
+    Local<Value> vals[] = { uid, did_throw };
+    if (post_fn->Call(context, ARRAY_SIZE(vals), vals).IsEmpty())
       FatalError("node::AsyncWrap::MakeCallback", "post hook threw");
   }
 

src/node.cc

@@ -1200,7 +1200,12 @@ Local<Value> MakeCallback(Environment* env,
   Local<Value> ret = callback->Call(recv, argc, argv);
 
   if (ran_init_callback && !post_fn.IsEmpty()) {
-    if (post_fn->Call(object, 0, nullptr).IsEmpty())
+    Local<Value> did_throw = Boolean::New(env->isolate(), ret.IsEmpty());
+    // Currently there's no way to retrieve an uid from node::MakeCallback().
+    // This needs to be fixed.
+    Local<Value> vals[] =
+        { Undefined(env->isolate()).As<Value>(), did_throw };
+    if (post_fn->Call(object, ARRAY_SIZE(vals), vals).IsEmpty())
       FatalError("node::MakeCallback", "post hook threw");
   }
 

test/parallel/test-async-wrap-post-did-throw.js

@@ -0,0 +1,34 @@
+'use strict';
+
+require('../common');
+const assert = require('assert');
+const async_wrap = process.binding('async_wrap');
+var asyncThrows = 0;
+var uncaughtExceptionCount = 0;
+
+process.on('uncaughtException', (e) => {
+  assert.equal(e.message, 'oh noes!', 'error messages do not match');
+});
+
+process.on('exit', () => {
+  process.removeAllListeners('uncaughtException');
+  assert.equal(uncaughtExceptionCount, 1);
+  assert.equal(uncaughtExceptionCount, asyncThrows);
+});
+
+function init() { }
+function post(id, threw) {
+  if (threw)
+    uncaughtExceptionCount++;
+}
+
+async_wrap.setupHooks({ init, post });
+async_wrap.enable();
+
+// Timers still aren't supported, so use crypto API.
+// It's also important that the callback not happen in a nextTick, like many
+// error events in core.
+require('crypto').randomBytes(0, () => {
+  asyncThrows++;
+  throw new Error('oh noes!');
+});