From c182c32183c77330bda0d1a433fedebc149f1e6c Mon Sep 17 00:00:00 2001
From: tsctx <91457664+tsctx@users.noreply.github.com>
Date: Mon, 27 Nov 2023 23:39:24 +0900
Subject: [PATCH] perf: avoid Headers initialization (#2468)

---
 lib/cache/symbols.js  |  2 +-
 lib/core/symbols.js   |  3 ++-
 lib/fetch/headers.js  |  5 ++++-
 lib/fetch/request.js  | 11 +++++------
 lib/fetch/response.js |  4 ++--
 5 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/lib/cache/symbols.js b/lib/cache/symbols.js
index f9b19740af8..40448d6001e 100644
--- a/lib/cache/symbols.js
+++ b/lib/cache/symbols.js
@@ -1,5 +1,5 @@
 'use strict'
 
 module.exports = {
-  kConstruct: Symbol('constructable')
+  kConstruct: require('../core/symbols').kConstruct
 }
diff --git a/lib/core/symbols.js b/lib/core/symbols.js
index 1d5dc4e3db0..68d8566fac0 100644
--- a/lib/core/symbols.js
+++ b/lib/core/symbols.js
@@ -58,5 +58,6 @@ module.exports = {
   kHTTP1BuildRequest: Symbol('http1 build request'),
   kHTTP2CopyHeaders: Symbol('http2 copy headers'),
   kHTTPConnVersion: Symbol('http connection version'),
-  kRetryHandlerDefaultRetry: Symbol('retry agent default retry')
+  kRetryHandlerDefaultRetry: Symbol('retry agent default retry'),
+  kConstruct: Symbol('constructable')
 }
diff --git a/lib/fetch/headers.js b/lib/fetch/headers.js
index 69acaaad996..2f1c0be5a47 100644
--- a/lib/fetch/headers.js
+++ b/lib/fetch/headers.js
@@ -2,7 +2,7 @@
 
 'use strict'
 
-const { kHeadersList } = require('../core/symbols')
+const { kHeadersList, kConstruct } = require('../core/symbols')
 const { kGuard } = require('./symbols')
 const { kEnumerableProperty } = require('../core/util')
 const {
@@ -240,6 +240,9 @@ class HeadersList {
 // https://fetch.spec.whatwg.org/#headers-class
 class Headers {
   constructor (init = undefined) {
+    if (init === kConstruct) {
+      return
+    }
     this[kHeadersList] = new HeadersList()
 
     // The new Headers(init) constructor steps are:
diff --git a/lib/fetch/request.js b/lib/fetch/request.js
index 3b813aa77df..51896f58435 100644
--- a/lib/fetch/request.js
+++ b/lib/fetch/request.js
@@ -28,13 +28,12 @@ const { kHeaders, kSignal, kState, kGuard, kRealm } = require('./symbols')
 const { webidl } = require('./webidl')
 const { getGlobalOrigin } = require('./global')
 const { URLSerializer } = require('./dataURL')
-const { kHeadersList } = require('../core/symbols')
+const { kHeadersList, kConstruct } = require('../core/symbols')
 const assert = require('assert')
 const { getMaxListeners, setMaxListeners, getEventListeners, defaultMaxListeners } = require('events')
 
 let TransformStream = globalThis.TransformStream
 
-const kInit = Symbol('init')
 const kAbortController = Symbol('abortController')
 
 const requestFinalizer = new FinalizationRegistry(({ signal, abort }) => {
@@ -45,7 +44,7 @@ const requestFinalizer = new FinalizationRegistry(({ signal, abort }) => {
 class Request {
   // https://fetch.spec.whatwg.org/#dom-request
   constructor (input, init = {}) {
-    if (input === kInit) {
+    if (input === kConstruct) {
       return
     }
 
@@ -398,7 +397,7 @@ class Request {
     // 30. Set this’s headers to a new Headers object with this’s relevant
     // Realm, whose header list is request’s header list and guard is
     // "request".
-    this[kHeaders] = new Headers()
+    this[kHeaders] = new Headers(kConstruct)
     this[kHeaders][kHeadersList] = request.headersList
     this[kHeaders][kGuard] = 'request'
     this[kHeaders][kRealm] = this[kRealm]
@@ -725,10 +724,10 @@ class Request {
 
     // 3. Let clonedRequestObject be the result of creating a Request object,
     // given clonedRequest, this’s headers’s guard, and this’s relevant Realm.
-    const clonedRequestObject = new Request(kInit)
+    const clonedRequestObject = new Request(kConstruct)
     clonedRequestObject[kState] = clonedRequest
     clonedRequestObject[kRealm] = this[kRealm]
-    clonedRequestObject[kHeaders] = new Headers()
+    clonedRequestObject[kHeaders] = new Headers(kConstruct)
     clonedRequestObject[kHeaders][kHeadersList] = clonedRequest.headersList
     clonedRequestObject[kHeaders][kGuard] = this[kHeaders][kGuard]
     clonedRequestObject[kHeaders][kRealm] = this[kHeaders][kRealm]
diff --git a/lib/fetch/response.js b/lib/fetch/response.js
index 23cf55c51dc..5d23475f14e 100644
--- a/lib/fetch/response.js
+++ b/lib/fetch/response.js
@@ -23,7 +23,7 @@ const { webidl } = require('./webidl')
 const { FormData } = require('./formdata')
 const { getGlobalOrigin } = require('./global')
 const { URLSerializer } = require('./dataURL')
-const { kHeadersList } = require('../core/symbols')
+const { kHeadersList, kConstruct } = require('../core/symbols')
 const assert = require('assert')
 const { types } = require('util')
 
@@ -144,7 +144,7 @@ class Response {
     // 2. Set this’s headers to a new Headers object with this’s relevant
     // Realm, whose header list is this’s response’s header list and guard
     // is "response".
-    this[kHeaders] = new Headers()
+    this[kHeaders] = new Headers(kConstruct)
     this[kHeaders][kGuard] = 'response'
     this[kHeaders][kHeadersList] = this[kState].headersList
     this[kHeaders][kRealm] = this[kRealm]