async_hooks: remove promise object from resource

While it doesn't make any difference now. In the future PromiseHooks
could be refactored to provide an asyncId instead of the promise object.
That would make escape analysis on promises possible.

Escape analysis on promises could lead to a more efficient destroy hook,
if provide by PromiseHooks as well. But at the very least would allow
the destroy hook to be emitted earlier. The destroy hook not being
emitted on promises frequent enough is a known and reported issue.
See nodejs#14446 and
Jeff-Lewis/cls-hooked#11.

While all this is speculation for now, it all depends on the promise
object not being a part of the PromiseWrap resource object.

Ref: nodejs#14446
Ref: nodejs/diagnostics#188

doc/api/async_hooks.md

@@ -301,8 +301,7 @@ currently not considered public, but using the Embedder API, users can provide
 and document their own resource objects. For example, such a resource object
 could contain the SQL query being executed.
 
-In the case of Promises, the `resource` object will have `promise` property
-that refers to the `Promise` that is being initialized, and an
+In the case of Promises, the `resource` object will have an
 `isChainedPromise` property, set to `true` if the promise has a parent promise,
 and `false` otherwise. For example, in the case of `b = a.then(handler)`, `a` is
 considered a parent `Promise` of `b`. Here, `b` is considered a chained promise.

lib/domain.js

@@ -55,13 +55,6 @@ const asyncHook = createHook({
       // if this operation is created while in a domain, let's mark it
       pairing.set(asyncId, process.domain);
       resource.domain = process.domain;
-      if (resource.promise !== undefined &&
-          resource.promise instanceof Promise) {
-        // resource.promise instanceof Promise make sure that the
-        // promise comes from the same context
-        // see https://github.com/nodejs/node/issues/15673
-        resource.promise.domain = process.domain;
-      }
     }
   },
   before(asyncId) {

src/async_wrap.cc

@@ -185,16 +185,13 @@ class PromiseWrap : public AsyncWrap {
   SET_MEMORY_INFO_NAME(PromiseWrap)
   SET_SELF_SIZE(PromiseWrap)
 
-  static constexpr int kPromiseField = 1;
-  static constexpr int kIsChainedPromiseField = 2;
-  static constexpr int kInternalFieldCount = 3;
+  static constexpr int kIsChainedPromiseField = 1;
+  static constexpr int kInternalFieldCount = 2;
 
   static PromiseWrap* New(Environment* env,
                           Local<Promise> promise,
                           PromiseWrap* parent_wrap,
                           bool silent);
-  static void GetPromise(Local<String> property,
-                         const PropertyCallbackInfo<Value>& info);
   static void getIsChainedPromise(Local<String> property,
                                   const PropertyCallbackInfo<Value>& info);
 };
@@ -205,7 +202,6 @@ PromiseWrap* PromiseWrap::New(Environment* env,
                               bool silent) {
   Local<Object> object = env->promise_wrap_template()
                             ->NewInstance(env->context()).ToLocalChecked();
-  object->SetInternalField(PromiseWrap::kPromiseField, promise);
   object->SetInternalField(PromiseWrap::kIsChainedPromiseField,
                            parent_wrap != nullptr ?
                               v8::True(env->isolate()) :
@@ -215,11 +211,6 @@ PromiseWrap* PromiseWrap::New(Environment* env,
   return new PromiseWrap(env, object, silent);
 }
 
-void PromiseWrap::GetPromise(Local<String> property,
-                             const PropertyCallbackInfo<Value>& info) {
-  info.GetReturnValue().Set(info.Holder()->GetInternalField(kPromiseField));
-}
-
 void PromiseWrap::getIsChainedPromise(Local<String> property,
                                       const PropertyCallbackInfo<Value>& info) {
   info.GetReturnValue().Set(
@@ -315,9 +306,6 @@ static void SetupHooks(const FunctionCallbackInfo<Value>& args) {
     Local<ObjectTemplate> promise_wrap_template = ctor->InstanceTemplate();
     promise_wrap_template->SetInternalFieldCount(
         PromiseWrap::kInternalFieldCount);
-    promise_wrap_template->SetAccessor(
-        FIXED_ONE_BYTE_STRING(env->isolate(), "promise"),
-        PromiseWrap::GetPromise);
     promise_wrap_template->SetAccessor(
         FIXED_ONE_BYTE_STRING(env->isolate(), "isChainedPromise"),
         PromiseWrap::getIsChainedPromise);

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

@@ -4,7 +4,6 @@ const common = require('../common');
 const assert = require('assert');
 const async_hooks = require('async_hooks');
 const EXPECTED_INITS = 2;
-let p_resource = null;
 let p_er = null;
 let p_inits = 0;
 
@@ -23,7 +22,6 @@ const mustCallInit = common.mustCall(function init(id, type, tid, resource) {
   if (type !== 'PROMISE')
     return;
   p_inits++;
-  p_resource = resource.promise;
 }, EXPECTED_INITS);
 
 const hook = async_hooks.createHook({
@@ -36,7 +34,6 @@ new Promise(common.mustCall((res) => {
 })).then(common.mustCall((val) => {
   hook.enable().enable();
   const p = new Promise((res) => res(val));
-  assert.strictEqual(p, p_resource);
   hook.disable();
   return p;
 })).then(common.mustCall((val2) => {

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

@@ -21,11 +21,9 @@ async_hooks.createHook({
 }).enable();
 
 const a = Promise.resolve(42);
-const b = a.then(common.mustCall());
+a.then(common.mustCall());
 
 assert.strictEqual(initCalls[0].triggerId, 1);
 assert.strictEqual(initCalls[0].resource.isChainedPromise, false);
-assert.strictEqual(initCalls[0].resource.promise, a);
 assert.strictEqual(initCalls[1].triggerId, initCalls[0].id);
 assert.strictEqual(initCalls[1].resource.isChainedPromise, true);
-assert.strictEqual(initCalls[1].resource.promise, b);

test/parallel/test-domain-promise.js

@@ -50,7 +50,6 @@ const vm = require('vm');
   d2.run(common.mustCall(() => {
     p.then(common.mustCall((v) => {
       assert.strictEqual(process.domain, d2);
-      assert.strictEqual(p.domain, d1);
     }));
   }));
 }
@@ -64,9 +63,8 @@ const vm = require('vm');
   }));
 
   d2.run(common.mustCall(() => {
-    p.then(p.domain.bind(common.mustCall((v) => {
+    p.then(d1.bind(common.mustCall((v) => {
       assert.strictEqual(process.domain, d1);
-      assert.strictEqual(p.domain, d1);
     })));
   }));
 }
@@ -83,7 +81,6 @@ const vm = require('vm');
     d2.run(common.mustCall(() => {
       p.then(common.mustCall((v) => {
         assert.strictEqual(process.domain, d2);
-        assert.strictEqual(p.domain, d1);
       }));
     }));
   }));
@@ -100,7 +97,6 @@ const vm = require('vm');
   d2.run(common.mustCall(() => {
     p.catch(common.mustCall((v) => {
       assert.strictEqual(process.domain, d2);
-      assert.strictEqual(p.domain, d1);
     }));
   }));
 }