async_hooks: add AsyncResource.bind utility

Creates an internal AsyncResource and binds a function to it, ensuring that the function is invoked within execution context in which bind was called. PR-URL: #34574 Reviewed-By: Stephen Belanger <[email protected]> Reviewed-By: Gus Caplan <[email protected]> Reviewed-By: Matteo Collina <[email protected]> Reviewed-By: Andrey Pechkurov <[email protected]> Reviewed-By: Gerhard Stöbich <[email protected]>

Author: jasnell

doc/api/async_hooks.md

@@ -733,6 +733,32 @@ class DBQuery extends AsyncResource{
 }
 ```
 
+#### `static AsyncResource.bind(fn[, type])`
+<!-- YAML
+added: REPLACEME
+-->
+
+*`fn`{Function} The function to bind to the current execution context.
+*`type`{string} An optional name to associate with the underlying
+`AsyncResource`.
+
+Binds the given function to the current execution context.
+
+The returned function will have an `asyncResource` property referencing
+the `AsyncResource` to which the function is bound.
+
+#### `asyncResource.bind(fn)`
+<!-- YAML
+added: REPLACEME
+-->
+
+*`fn`{Function} The function to bind to the current `AsyncResource`.
+
+Binds the given function to execute to this `AsyncResource`'s scope.
+
+The returned function will have an `asyncResource` property referencing
+the `AsyncResource` to which the function is bound.
+
 #### `asyncResource.runInAsyncScope(fn[, thisArg, ...args])`
 <!-- YAML
 added: v9.6.0
@@ -904,12 +930,12 @@ const{createServer } = require('http');
 const{AsyncResource, executionAsyncId } =require('async_hooks');
 
 constserver=createServer((req, res) =>{
-constasyncResource=newAsyncResource('request');
-// The listener will always run in the execution context of `asyncResource`.
-req.on('close', asyncResource.runInAsyncScope.bind(asyncResource, () =>{
-// Prints: true
-console.log(asyncResource.asyncId() ===executionAsyncId());
+req.on('close', AsyncResource.bind(() =>{
+// Execution context is bound to the current outer scope.
  }));
+req.on('close', () =>{
+// Execution context is bound to the scope that caused 'close' to emit.
+ });
 res.end();
 }).listen(3000);
 ```

lib/async_hooks.js

@@ -2,13 +2,15 @@
 
 const{
  NumberIsSafeInteger,
+ ObjectDefineProperties,
  ReflectApply,
  Symbol,
 }=primordials;
 
 const{
 ERR_ASYNC_CALLBACK,
 ERR_ASYNC_TYPE,
+ERR_INVALID_ARG_TYPE,
 ERR_INVALID_ASYNC_ID
 }=require('internal/errors').codes;
 const{ validateString }=require('internal/validators');
@@ -208,6 +210,28 @@ class AsyncResource{
 triggerAsyncId(){
 returnthis[trigger_async_id_symbol];
 }
+
+bind(fn){
+if(typeoffn!=='function')
+thrownewERR_INVALID_ARG_TYPE('fn','Function',fn);
+constret=this.runInAsyncScope.bind(this,fn);
+ObjectDefineProperties(ret,{
+'length': {
+enumerable: true,
+value: fn.length,
+},
+'asyncResource': {
+enumerable: true,
+value: this,
+}
+});
+returnret;
+}
+
+staticbind(fn,type){
+type=type||fn.name;
+return(newAsyncResource(type||'bound-anonymous-fn')).bind(fn);
+}
 }
 
 conststorageList=[];

test/parallel/test-asyncresource-bind.js

@@ -0,0 +1,35 @@
+'use strict';
+
+constcommon=require('../common');
+constassert=require('assert');
+const{ AsyncResource, executionAsyncId }=require('async_hooks');
+
+constfn=common.mustCall(AsyncResource.bind(()=>{
+returnexecutionAsyncId();
+}));
+
+setImmediate(()=>{
+constasyncId=executionAsyncId();
+assert.notStrictEqual(asyncId,fn());
+});
+
+constasyncResource=newAsyncResource('test');
+
+[1,false,'',{},[]].forEach((i)=>{
+assert.throws(()=>asyncResource.bind(i),{
+code: 'ERR_INVALID_ARG_TYPE'
+});
+});
+
+constfn2=asyncResource.bind((a,b)=>{
+returnexecutionAsyncId();
+});
+
+assert.strictEqual(fn2.asyncResource,asyncResource);
+assert.strictEqual(fn2.length,2);
+
+setImmediate(()=>{
+constasyncId=executionAsyncId();
+assert.strictEqual(asyncResource.asyncId(),fn2());
+assert.notStrictEqual(asyncId,fn2());
+});