From 621f423d23e684108fb3d3224f7974c2a1291e2a Mon Sep 17 00:00:00 2001
From: Roch Devost <roch.devost@gmail.com>
Date: Mon, 28 Mar 2022 17:32:14 -0400
Subject: [PATCH] fix `AsyncResource.bind()` binding `this` to itself by
 default (#1942)

---
 .../src/helpers/instrument.js                 | 21 ++++++++++++++-----
 .../datadog-plugin-net/test/index.spec.js     |  3 ++-
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/packages/datadog-instrumentations/src/helpers/instrument.js b/packages/datadog-instrumentations/src/helpers/instrument.js
index 9108087acea..6689e9d8dd9 100644
--- a/packages/datadog-instrumentations/src/helpers/instrument.js
+++ b/packages/datadog-instrumentations/src/helpers/instrument.js
@@ -88,7 +88,9 @@ function getBasedir (id) {
   return parse(id).basedir.replace(pathSepExpr, '/')
 }
 
-if (semver.satisfies(process.versions.node, '>=16.0.0')) {
+// AsyncResource.bind exists and binds `this` properly only from 17.8.0 and up.
+// https://nodejs.org/api/async_context.html#asyncresourcebindfn-thisarg
+if (semver.satisfies(process.versions.node, '>=17.8.0')) {
   exports.AsyncResource = AsyncResource
 } else {
   exports.AsyncResource = class extends AsyncResource {
@@ -97,9 +99,18 @@ if (semver.satisfies(process.versions.node, '>=16.0.0')) {
       return (new exports.AsyncResource(type || 'bound-anonymous-fn')).bind(fn, thisArg)
     }
 
-    bind (fn, thisArg = this) {
-      const ret = this.runInAsyncScope.bind(this, fn, thisArg)
-      Object.defineProperties(ret, {
+    bind (fn, thisArg) {
+      let bound
+      if (thisArg === undefined) {
+        const resource = this
+        bound = function (...args) {
+          args.unshift(fn, this)
+          return Reflect.apply(resource.runInAsyncScope, resource, args)
+        }
+      } else {
+        bound = this.runInAsyncScope.bind(this, fn, thisArg)
+      }
+      Object.defineProperties(bound, {
         'length': {
           configurable: true,
           enumerable: false,
@@ -113,7 +124,7 @@ if (semver.satisfies(process.versions.node, '>=16.0.0')) {
           writable: true
         }
       })
-      return ret
+      return bound
     }
   }
 }
diff --git a/packages/datadog-plugin-net/test/index.spec.js b/packages/datadog-plugin-net/test/index.spec.js
index e23570d2c25..886101ad461 100644
--- a/packages/datadog-plugin-net/test/index.spec.js
+++ b/packages/datadog-plugin-net/test/index.spec.js
@@ -220,7 +220,8 @@ describe('Plugin', () => {
       const socket = new net.Socket()
 
       tracer.scope().activate(parent, () => {
-        socket.connect({ port }, () => {
+        socket.connect({ port }, function () {
+          expect(this).to.equal(socket)
           expect(tracer.scope().active()).to.equal(parent)
           socket.destroy()
           done()