async_hooks: proper id stacking for Promises

Until now, the async_hooks PromiseHook did not register the Promise’s
async id and trigger id on the id stack, so inside the `.then()` handler
those ids would be invalid.

To fix this, add push and pop calls to its `before` and `after` parts,
respectively. Some care needs to be taken for the cases that the
Promise hook is being disabled or enabled during the execution
of a Promise handler; in the former case, actually removing the hook
is delayed by adding another task to the microtask queue, in the latter
case popping the id off the async id stack is skipped if the ids don’t
match.

Fixes: https://github.com/nodejs/node/issues/13583
PR-URL: https://github.com/nodejs/node/pull/13585
Reviewed-By: Trevor Norris <trevnorris@gmail.com>

src/async-wrap.cc

@@ -333,12 +333,7 @@ void PromiseWrap::GetParentId(Local<String> property,
 
 static void PromiseHook(PromiseHookType type, Local<Promise> promise,
                         Local<Value> parent, void* arg) {
-  Local<Context> context = promise->CreationContext();
-  Environment* env = Environment::GetCurrent(context);
-
-  // PromiseHook() should never be called if no hooks have been enabled.
-  CHECK_GT(env->async_hooks()->fields()[AsyncHooks::kTotals], 0);
-
+  Environment* env = static_cast<Environment*>(arg);
   Local<Value> resource_object_value = promise->GetInternalField(0);
   PromiseWrap* wrap = nullptr;
   if (resource_object_value->IsObject()) {
@@ -376,9 +371,18 @@ static void PromiseHook(PromiseHookType type, Local<Promise> promise,
 
   CHECK_NE(wrap, nullptr);
   if (type == PromiseHookType::kBefore) {
+    env->async_hooks()->push_ids(wrap->get_id(), wrap->get_trigger_id());
     PreCallbackExecution(wrap, false);
   } else if (type == PromiseHookType::kAfter) {
     PostCallbackExecution(wrap, false);
+    if (env->current_async_id() == wrap->get_id()) {
+      // This condition might not be true if async_hooks was enabled during
+      // the promise callback execution.
+      // Popping it off the stack can be skipped in that case, because is is
+      // known that it would correspond to exactly one call with
+      // PromiseHookType::kBefore that was not witnessed by the PromiseHook.
+      env->async_hooks()->pop_ids(wrap->get_id());
+    }
   }
 }
 
@@ -429,13 +433,19 @@ static void SetupHooks(const FunctionCallbackInfo<Value>& args) {
 
 static void EnablePromiseHook(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
-  env->AddPromiseHook(PromiseHook, nullptr);
+  env->AddPromiseHook(PromiseHook, static_cast<void*>(env));
 }
 
 
 static void DisablePromiseHook(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
-  env->RemovePromiseHook(PromiseHook, nullptr);
+
+  // Delay the call to `RemovePromiseHook` because we might currently be
+  // between the `before` and `after` calls of a Promise.
+  env->isolate()->EnqueueMicrotask([](void* data) {
+    Environment* env = static_cast<Environment*>(data);
+    env->RemovePromiseHook(PromiseHook, data);
+  }, static_cast<void*>(env));
 }
 
 

src/env.cc

@@ -184,8 +184,11 @@ void Environment::AddPromiseHook(promise_hook_func fn, void* arg) {
       [&](const PromiseHookCallback& hook) {
         return hook.cb_ == fn && hook.arg_ == arg;
       });
-  CHECK_EQ(it, promise_hooks_.end());
-  promise_hooks_.push_back(PromiseHookCallback{fn, arg});
+  if (it != promise_hooks_.end()) {
+    it->enable_count_++;
+    return;
+  }
+  promise_hooks_.push_back(PromiseHookCallback{fn, arg, 1});
 
   if (promise_hooks_.size() == 1) {
     isolate_->SetPromiseHook(EnvPromiseHook);
@@ -201,6 +204,8 @@ bool Environment::RemovePromiseHook(promise_hook_func fn, void* arg) {
 
   if (it == promise_hooks_.end()) return false;
 
+  if (--it->enable_count_ > 0) return true;
+
   promise_hooks_.erase(it);
   if (promise_hooks_.empty()) {
     isolate_->SetPromiseHook(nullptr);

src/env.h

@@ -722,6 +722,7 @@ class Environment {
   struct PromiseHookCallback {
     promise_hook_func cb_;
     void* arg_;
+    size_t enable_count_;
   };
   std::vector<PromiseHookCallback> promise_hooks_;
 

test/addons/async-hooks-promise/test.js

@@ -36,8 +36,12 @@ assert.strictEqual(
 
 hook1.disable();
 
-// Check that internal fields are no longer being set.
-assert.strictEqual(
-  binding.getPromiseField(Promise.resolve(1)),
-  0,
-  'Promise internal field used despite missing enabled AsyncHook');
+// Check that internal fields are no longer being set. This needs to be delayed
+// a bit because the `disable()` call only schedules disabling the hook in a
+// future microtask.
+setImmediate(() => {
+  assert.strictEqual(
+    binding.getPromiseField(Promise.resolve(1)),
+    0,
+    'Promise internal field used despite missing enabled AsyncHook');
+});

test/parallel/test-async-hooks-disable-during-promise.js

@@ -0,0 +1,17 @@
+'use strict';
+const common = require('../common');
+const async_hooks = require('async_hooks');
+
+const hook = async_hooks.createHook({
+  init: common.mustCall(2),
+  before: common.mustCall(1),
+  after: common.mustNotCall()
+}).enable();
+
+Promise.resolve(1).then(common.mustCall(() => {
+  hook.disable();
+
+  Promise.resolve(42).then(common.mustCall());
+
+  process.nextTick(common.mustCall());
+}));

test/parallel/test-async-hooks-enable-during-promise.js

@@ -0,0 +1,13 @@
+'use strict';
+const common = require('../common');
+const async_hooks = require('async_hooks');
+
+Promise.resolve(1).then(common.mustCall(() => {
+  async_hooks.createHook({
+    init: common.mustCall(),
+    before: common.mustCall(),
+    after: common.mustCall(2)
+  }).enable();
+
+  process.nextTick(common.mustCall());
+}));

test/parallel/test-async-hooks-promise-triggerid.js

@@ -0,0 +1,32 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const async_hooks = require('async_hooks');
+
+common.crashOnUnhandledRejection();
+
+const promiseAsyncIds = [];
+
+async_hooks.createHook({
+  init: common.mustCallAtLeast((id, type, triggerId) => {
+    if (type === 'PROMISE') {
+      // Check that the last known Promise is triggering the creation of
+      // this one.
+      assert.strictEqual(promiseAsyncIds[promiseAsyncIds.length - 1] || 1,
+                         triggerId);
+      promiseAsyncIds.push(id);
+    }
+  }, 3),
+  before: common.mustCall((id) => {
+    assert.strictEqual(id, promiseAsyncIds[1]);
+  }),
+  after: common.mustCall((id) => {
+    assert.strictEqual(id, promiseAsyncIds[1]);
+  })
+}).enable();
+
+Promise.resolve(42).then(common.mustCall(() => {
+  assert.strictEqual(async_hooks.executionAsyncId(), promiseAsyncIds[1]);
+  assert.strictEqual(async_hooks.triggerAsyncId(), promiseAsyncIds[0]);
+  Promise.resolve(10);
+}));