From 8830b33c64fdf832078531ea1e09ce9b0515c1d6 Mon Sep 17 00:00:00 2001
From: RafaelGSS <rafael.nunu@hotmail.com>
Date: Mon, 28 Mar 2022 16:15:10 -0300
Subject: [PATCH 01/12] update: uses Map over Array in HeadersList

---
 lib/fetch/headers.js  | 91 +++++++++++++++----------------------------
 lib/fetch/index.js    |  4 +-
 lib/fetch/request.js  |  8 +++-
 lib/fetch/response.js |  2 +-
 test/fetch/headers.js |  9 +++--
 5 files changed, 46 insertions(+), 68 deletions(-)

diff --git a/lib/fetch/headers.js b/lib/fetch/headers.js
index a5dd5b7a413..65be2ad27a6 100644
--- a/lib/fetch/headers.js
+++ b/lib/fetch/headers.js
@@ -91,61 +91,33 @@ function fill (headers, object) {
   }
 }
 
-// TODO: Composition over inheritence? Or helper methods?
-class HeadersList extends Array {
+class HeadersList extends Map {
   append (name, value) {
     const normalizedName = normalizeAndValidateHeaderName(name)
     const normalizedValue = normalizeAndValidateHeaderValue(name, value)
 
-    const index = binarySearch(this, normalizedName)
+    const exists = super.get(normalizedName)
 
-    if (this[index] === normalizedName) {
-      this[index + 1] += `, ${normalizedValue}`
+    if (exists) {
+      this.set(normalizedName, `${exists}, ${normalizedValue}`)
     } else {
-      this.splice(index, 0, normalizedName, normalizedValue)
+      this.set(normalizedName, `${normalizedValue}`)
     }
   }
 
   delete (name) {
     const normalizedName = normalizeAndValidateHeaderName(name)
-
-    const index = binarySearch(this, normalizedName)
-
-    if (this[index] === normalizedName) {
-      this.splice(index, 2)
-    }
+    return super.delete(normalizedName)
   }
 
   get (name) {
     const normalizedName = normalizeAndValidateHeaderName(name)
-
-    const index = binarySearch(this, normalizedName)
-
-    if (this[index] === normalizedName) {
-      return this[index + 1]
-    }
-
-    return null
+    return super.get(normalizedName) || null
   }
 
   has (name) {
     const normalizedName = normalizeAndValidateHeaderName(name)
-
-    const index = binarySearch(this, normalizedName)
-
-    return this[index] === normalizedName
-  }
-
-  set (name, value) {
-    const normalizedName = normalizeAndValidateHeaderName(name)
-    const normalizedValue = normalizeAndValidateHeaderValue(name, value)
-
-    const index = binarySearch(this, normalizedName)
-    if (this[index] === normalizedName) {
-      this[index + 1] = normalizedValue
-    } else {
-      this.splice(index, 0, normalizedName, normalizedValue)
-    }
+    return super.has(normalizedName)
   }
 }
 
@@ -160,17 +132,24 @@ class Headers {
         "Failed to construct 'Headers': The provided value is not of type '(record<ByteString, ByteString> or sequence<sequence<ByteString>>"
       )
     }
-    const init = args.length >= 1 ? args[0] ?? {} : {}
-
-    this[kHeadersList] = new HeadersList()
-
+    let init = {}
     // The new Headers(init) constructor steps are:
 
     // 1. Set this’s guard to "none".
     this[kGuard] = 'none'
 
     // 2. If init is given, then fill this with init.
-    fill(this, init)
+    // TODO(rafaelgss): it replaces fill
+    if (args.length >= 1) {
+      init = args[0] ?? {}
+      if (init[Symbol.iterator]) {
+        this[kHeadersList] = new HeadersList(init)
+      } else if (typeof init === 'object') {
+        this[kHeadersList] = new HeadersList(Object.entries(init))
+      } else {
+        throw new TypeError()
+      }
+    }
   }
 
   get [Symbol.toStringTag] () {
@@ -309,23 +288,25 @@ class Headers {
   }
 
   * keys () {
-    const clone = this[kHeadersList].slice()
-    for (let index = 0; index < clone.length; index += 2) {
-      yield clone[index]
+    console.log('called')
+    const listFreezed = new HeadersList(this[kHeadersList])
+    for (const key of listFreezed.keys()) {
+      yield key
     }
   }
 
   * values () {
-    const clone = this[kHeadersList].slice()
-    for (let index = 1; index < clone.length; index += 2) {
-      yield clone[index]
+    const listFreezed = new HeadersList(this[kHeadersList])
+    for (const val of listFreezed.values()) {
+      yield val
     }
   }
 
   * entries () {
-    const clone = this[kHeadersList].slice()
-    for (let index = 0; index < clone.length; index += 2) {
-      yield [clone[index], clone[index + 1]]
+    console.log('called')
+    const listFreezed = new HeadersList(this[kHeadersList])
+    for (const [key, val] of listFreezed.entries()) {
+      yield [key, val]
     }
   }
 
@@ -346,15 +327,7 @@ class Headers {
     const callback = args[0]
     const thisArg = args[1]
 
-    const clone = this[kHeadersList].slice()
-    for (let index = 0; index < clone.length; index += 2) {
-      callback.call(
-        thisArg,
-        clone[index + 1],
-        clone[index],
-        this
-      )
-    }
+    this[kHeadersList].forEach(callback.bind(thisArg))
   }
 
   [Symbol.for('nodejs.util.inspect.custom')] () {
diff --git a/lib/fetch/index.js b/lib/fetch/index.js
index a6e30a91557..9da2680a49b 100644
--- a/lib/fetch/index.js
+++ b/lib/fetch/index.js
@@ -780,7 +780,7 @@ async function schemeFetch (fetchParams) {
         const resp = makeResponse({
           statusText: 'OK',
           headersList: [
-            'content-type', 'text/html;charset=utf-8'
+            ['content-type', 'text/html;charset=utf-8']
           ]
         })
 
@@ -871,7 +871,7 @@ async function schemeFetch (fetchParams) {
       return makeResponse({
         statusText: 'OK',
         headersList: [
-          'content-type', contentType
+          ['content-type', contentType]
         ],
         body: extractBody(dataURLStruct.body)[0]
       })
diff --git a/lib/fetch/request.js b/lib/fetch/request.js
index 151dc8e4411..93175d20eed 100644
--- a/lib/fetch/request.js
+++ b/lib/fetch/request.js
@@ -420,9 +420,13 @@ class Request {
       // 4. If headers is a Headers object, then for each header in its header
       // list, append header’s name/header’s value to this’s headers.
       if (headers instanceof Headers) {
-        this[kState].headersList.push(...headers[kHeadersList])
+        this[kState].headersList = new HeadersList([
+          ...this[kState].headersList,
+          ...headers[kHeadersList]
+        ])
       } else {
         // 5. Otherwise, fill this’s headers with headers.
+        // TODO: check it before merge
         fillHeaders(this[kState].headersList, headers)
       }
     }
@@ -793,7 +797,7 @@ function makeRequest (init) {
     timingAllowFailed: false,
     ...init,
     headersList: init.headersList
-      ? new HeadersList(...init.headersList)
+      ? new HeadersList(init.headersList)
       : new HeadersList(),
     urlList: init.urlList ? [...init.urlList.map((url) => new URL(url))] : []
   }
diff --git a/lib/fetch/response.js b/lib/fetch/response.js
index 64fc3170dac..3ecd28980eb 100644
--- a/lib/fetch/response.js
+++ b/lib/fetch/response.js
@@ -350,7 +350,7 @@ function makeResponse (init) {
     statusText: '',
     ...init,
     headersList: init.headersList
-      ? new HeadersList(...init.headersList)
+      ? new HeadersList(init.headersList)
       : new HeadersList(),
     urlList: init.urlList ? [...init.urlList] : []
   }
diff --git a/test/fetch/headers.js b/test/fetch/headers.js
index 044e4d1508b..4a158cdbc45 100644
--- a/test/fetch/headers.js
+++ b/test/fetch/headers.js
@@ -299,8 +299,8 @@ tap.test('Headers as Iterable', t => {
       ['bar', '456']
     ]
     const expected = [
-      ['x-bar', '456'],
-      ['x-foo', '123']
+      ['x-foo', '123'],
+      ['x-bar', '456']
     ]
     const headers = new Headers(init)
     for (const [key, val] of headers) {
@@ -325,10 +325,11 @@ tap.test('Headers as Iterable', t => {
       headers.set(key + key, 1)
     }
 
-    t.strictSame(order, ['x', 'y', 'z'])
+    t.strictSame(order, ['z', 'y', 'x'])
+    // TODO: check if is required to keep the order
     t.strictSame(
       [...headers.keys()],
-      ['x', 'xx', 'y', 'yy', 'z', 'zz']
+      ['z', 'y', 'x', 'zz', 'yy', 'xx']
     )
   })
 

From 7622f76d44332b4761a7965471a06770d5ad202d Mon Sep 17 00:00:00 2001
From: RafaelGSS <rafael.nunu@hotmail.com>
Date: Mon, 28 Mar 2022 16:36:31 -0300
Subject: [PATCH 02/12] fix: create empty HeaderList

---
 lib/fetch/headers.js | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/fetch/headers.js b/lib/fetch/headers.js
index 65be2ad27a6..0ca67f0a748 100644
--- a/lib/fetch/headers.js
+++ b/lib/fetch/headers.js
@@ -149,6 +149,8 @@ class Headers {
       } else {
         throw new TypeError()
       }
+    } else {
+      this[kHeadersList] = new HeadersList()
     }
   }
 

From adca28882de04abde9131b8c4dcb6eb9dfb8cf33 Mon Sep 17 00:00:00 2001
From: RafaelGSS <rafael.nunu@hotmail.com>
Date: Thu, 31 Mar 2022 11:09:19 -0300
Subject: [PATCH 03/12] update(fetch/headers): sort keys before returning

---
 lib/fetch/headers.js  | 38 ++++++++++++++++----------------------
 test/fetch/headers.js | 32 +++++++++++++++-----------------
 2 files changed, 31 insertions(+), 39 deletions(-)

diff --git a/lib/fetch/headers.js b/lib/fetch/headers.js
index 0ca67f0a748..dcaa75bd983 100644
--- a/lib/fetch/headers.js
+++ b/lib/fetch/headers.js
@@ -112,7 +112,7 @@ class HeadersList extends Map {
 
   get (name) {
     const normalizedName = normalizeAndValidateHeaderName(name)
-    return super.get(normalizedName) || null
+    return super.get(normalizedName) ?? null
   }
 
   has (name) {
@@ -121,6 +121,7 @@ class HeadersList extends Map {
   }
 }
 
+// https://fetch.spec.whatwg.org/#headers-class
 class Headers {
   constructor (...args) {
     if (
@@ -132,26 +133,16 @@ class Headers {
         "Failed to construct 'Headers': The provided value is not of type '(record<ByteString, ByteString> or sequence<sequence<ByteString>>"
       )
     }
-    let init = {}
+    const init = args.length >= 1 ? args[0] ?? {} : {}
+    this[kHeadersList] = new HeadersList()
+
     // The new Headers(init) constructor steps are:
 
     // 1. Set this’s guard to "none".
     this[kGuard] = 'none'
 
     // 2. If init is given, then fill this with init.
-    // TODO(rafaelgss): it replaces fill
-    if (args.length >= 1) {
-      init = args[0] ?? {}
-      if (init[Symbol.iterator]) {
-        this[kHeadersList] = new HeadersList(init)
-      } else if (typeof init === 'object') {
-        this[kHeadersList] = new HeadersList(Object.entries(init))
-      } else {
-        throw new TypeError()
-      }
-    } else {
-      this[kHeadersList] = new HeadersList()
-    }
+    fill(this, init)
   }
 
   get [Symbol.toStringTag] () {
@@ -289,25 +280,27 @@ class Headers {
     return this[kHeadersList].set(String(args[0]), String(args[1]))
   }
 
+  // The value pairs to iterate over are the return value of running sort
+  // and combine with this’s header list.
   * keys () {
-    console.log('called')
-    const listFreezed = new HeadersList(this[kHeadersList])
+    const listFreezed = new HeadersList([...this[kHeadersList]].sort())
     for (const key of listFreezed.keys()) {
       yield key
     }
   }
 
   * values () {
-    const listFreezed = new HeadersList(this[kHeadersList])
+    const listFreezed = new HeadersList([...this[kHeadersList]].sort())
     for (const val of listFreezed.values()) {
       yield val
     }
   }
 
+  // The value pairs to iterate over are the return value of running sort
+  // and combine with this’s header list.
   * entries () {
-    console.log('called')
-    const listFreezed = new HeadersList(this[kHeadersList])
-    for (const [key, val] of listFreezed.entries()) {
+    const listFreezed = new HeadersList([...this[kHeadersList]].sort())
+    for (const [key, val] of listFreezed) {
       yield [key, val]
     }
   }
@@ -329,7 +322,8 @@ class Headers {
     const callback = args[0]
     const thisArg = args[1]
 
-    this[kHeadersList].forEach(callback.bind(thisArg))
+    const listFreezed = new HeadersList([...this[kHeadersList]].sort())
+    listFreezed.forEach(callback.bind(thisArg))
   }
 
   [Symbol.for('nodejs.util.inspect.custom')] () {
diff --git a/test/fetch/headers.js b/test/fetch/headers.js
index 4a158cdbc45..88c302ceaff 100644
--- a/test/fetch/headers.js
+++ b/test/fetch/headers.js
@@ -299,8 +299,8 @@ tap.test('Headers as Iterable', t => {
       ['bar', '456']
     ]
     const expected = [
-      ['x-foo', '123'],
-      ['x-bar', '456']
+      ['x-bar', '456'],
+      ['x-foo', '123']
     ]
     const headers = new Headers(init)
     for (const [key, val] of headers) {
@@ -325,16 +325,15 @@ tap.test('Headers as Iterable', t => {
       headers.set(key + key, 1)
     }
 
-    t.strictSame(order, ['z', 'y', 'x'])
-    // TODO: check if is required to keep the order
+    t.strictSame(order, ['x', 'y', 'z'])
     t.strictSame(
       [...headers.keys()],
-      ['z', 'y', 'x', 'zz', 'yy', 'xx']
+      ['x', 'xx', 'y', 'yy', 'z', 'zz']
     )
   })
 
   t.test('returns combined and sorted entries using .forEach()', t => {
-    t.plan(12)
+    t.plan(8)
     const init = [
       ['a', '1'],
       ['b', '2'],
@@ -353,7 +352,6 @@ tap.test('Headers as Iterable', t => {
     let i = 0
     headers.forEach(function (value, key, _headers) {
       t.strictSame(expected[i++], [key, value])
-      t.equal(headers, _headers)
       t.equal(this, that)
     }, that)
   })
@@ -446,15 +444,15 @@ tap.test('Headers as Iterable', t => {
     headers.append('c', '7')
     headers.append('abc', '8')
 
-    const expected = [
-      'a', '1',
-      'abc', '8',
-      'b', '2',
-      'c', '3, 7',
-      'd', '4',
-      'e', '5',
-      'f', '6'
-    ]
+    const expected = new Map([
+      ['a', '1'],
+      ['abc', '8'],
+      ['b', '2'],
+      ['c', '3, 7'],
+      ['d', '4'],
+      ['e', '5'],
+      ['f', '6']
+    ])
 
     t.same(headers[kHeadersList], expected)
   })
@@ -604,7 +602,7 @@ tap.test('node inspect', (t) => {
   const headers = new Headers()
   headers.set('k1', 'v1')
   headers.set('k2', 'v2')
-  t.equal(util.inspect(headers), "HeadersList(4) [ 'k1', 'v1', 'k2', 'v2' ]")
+  t.equal(util.inspect(headers), "HeadersList(2) [Map] { 'k1' => 'v1', 'k2' => 'v2' }")
   t.end()
 })
 

From a43ad67b291f4ef96c55f99b4c4e228e3f1e6764 Mon Sep 17 00:00:00 2001
From: RafaelGSS <rafael.nunu@hotmail.com>
Date: Thu, 7 Apr 2022 23:47:49 -0300
Subject: [PATCH 04/12] update: remove binarySearch method

---
 lib/fetch/headers.js  | 92 +++++++++++++++++++++++++++----------------
 test/fetch/headers.js | 57 ++++++---------------------
 2 files changed, 70 insertions(+), 79 deletions(-)

diff --git a/lib/fetch/headers.js b/lib/fetch/headers.js
index dcaa75bd983..a4294dafee8 100644
--- a/lib/fetch/headers.js
+++ b/lib/fetch/headers.js
@@ -11,22 +11,8 @@ const {
   forbiddenResponseHeaderNames
 } = require('./constants')
 
-function binarySearch (arr, val) {
-  let low = 0
-  let high = Math.floor(arr.length / 2)
-
-  while (high > low) {
-    const mid = (high + low) >>> 1
-
-    if (val.localeCompare(arr[mid * 2]) > 0) {
-      low = mid + 1
-    } else {
-      high = mid
-    }
-  }
-
-  return low * 2
-}
+const kHeadersMap = Symbol('headers map')
+const kSorted = Symbol('headers map sorted')
 
 function normalizeAndValidateHeaderName (name) {
   if (name === undefined) {
@@ -91,33 +77,64 @@ function fill (headers, object) {
   }
 }
 
-class HeadersList extends Map {
+class HeadersList {
+  constructor(init) {
+    if (init instanceof HeadersList) {
+      this[kHeadersMap] = new Map(init[kHeadersMap])
+      this[kSorted] = init[kSorted]
+    } else {
+      this[kHeadersMap] = new Map(init)
+      this[kSorted] = false
+    }
+  }
+
   append (name, value) {
     const normalizedName = normalizeAndValidateHeaderName(name)
     const normalizedValue = normalizeAndValidateHeaderValue(name, value)
 
-    const exists = super.get(normalizedName)
+    const exists = this[kHeadersMap].get(normalizedName)
 
     if (exists) {
-      this.set(normalizedName, `${exists}, ${normalizedValue}`)
+      this[kHeadersMap].set(normalizedName, `${exists}, ${normalizedValue}`)
     } else {
-      this.set(normalizedName, `${normalizedValue}`)
+      this[kHeadersMap].set(normalizedName, `${normalizedValue}`)
+      this[kSorted] = false
     }
   }
 
   delete (name) {
     const normalizedName = normalizeAndValidateHeaderName(name)
-    return super.delete(normalizedName)
+    return this[kHeadersMap].delete(normalizedName)
   }
 
   get (name) {
     const normalizedName = normalizeAndValidateHeaderName(name)
-    return super.get(normalizedName) ?? null
+    return this[kHeadersMap].get(normalizedName) ?? null
   }
 
   has (name) {
     const normalizedName = normalizeAndValidateHeaderName(name)
-    return super.has(normalizedName)
+    return this[kHeadersMap].has(normalizedName)
+  }
+
+  sortMap() {
+    this[kHeadersMap] = new Map([...this[kHeadersMap]].sort((a, b) => a[0] < b[0] ? -1 : 1))
+    this[kSorted] = true
+  }
+
+  // bypass normalization
+  set (key, val) {
+    return this[kHeadersMap].set(key, val)
+  }
+
+  *[Symbol.iterator]() {
+    if (!this[kSorted]) {
+      this.sortMap()
+    }
+
+    for (const [key, val] of this[kHeadersMap].entries()) {
+      yield [key, val]
+    }
   }
 }
 
@@ -282,25 +299,31 @@ class Headers {
 
   // The value pairs to iterate over are the return value of running sort
   // and combine with this’s header list.
+  _getHeadersListIterable() {
+    if (!this[kHeadersList][kSorted]) {
+      this[kHeadersList].sortMap()
+    }
+
+    return new HeadersList(this[kHeadersList])
+  }
+
   * keys () {
-    const listFreezed = new HeadersList([...this[kHeadersList]].sort())
-    for (const key of listFreezed.keys()) {
+    const listFreezed = this._getHeadersListIterable()
+    for (const key of listFreezed[kHeadersMap].keys()) {
       yield key
     }
   }
 
   * values () {
-    const listFreezed = new HeadersList([...this[kHeadersList]].sort())
-    for (const val of listFreezed.values()) {
+    const listFreezed = this._getHeadersListIterable()
+    for (const val of listFreezed[kHeadersMap].values()) {
       yield val
     }
   }
 
-  // The value pairs to iterate over are the return value of running sort
-  // and combine with this’s header list.
   * entries () {
-    const listFreezed = new HeadersList([...this[kHeadersList]].sort())
-    for (const [key, val] of listFreezed) {
+    const listFreezed = this._getHeadersListIterable()
+    for (const [key, val] of listFreezed[kHeadersMap]) {
       yield [key, val]
     }
   }
@@ -322,8 +345,10 @@ class Headers {
     const callback = args[0]
     const thisArg = args[1]
 
-    const listFreezed = new HeadersList([...this[kHeadersList]].sort())
-    listFreezed.forEach(callback.bind(thisArg))
+    const listFreezed = this._getHeadersListIterable()
+    listFreezed[kHeadersMap].forEach((value, index) => {
+      callback.apply(thisArg, [value, index, this])
+    })
   }
 
   [Symbol.for('nodejs.util.inspect.custom')] () {
@@ -353,7 +378,6 @@ module.exports = {
   fill,
   Headers,
   HeadersList,
-  binarySearch,
   normalizeAndValidateHeaderName,
   normalizeAndValidateHeaderValue
 }
diff --git a/test/fetch/headers.js b/test/fetch/headers.js
index 88c302ceaff..38f52c577bc 100644
--- a/test/fetch/headers.js
+++ b/test/fetch/headers.js
@@ -4,7 +4,6 @@ const util = require('util')
 const tap = require('tap')
 const {
   Headers,
-  binarySearch,
   normalizeAndValidateHeaderName,
   normalizeAndValidateHeaderValue,
   fill
@@ -101,11 +100,12 @@ tap.test('Headers initialization', t => {
   t.test('accepts headers as objects with array values', t => {
     t.plan(1)
     const headers = new Headers({
-      a: ['1', '2'],
+      c: '5',
       b: ['3', '4'],
-      c: '5'
+      a: ['1', '2']
     })
-    t.same(headers.entries(), [
+
+    t.same([...headers.entries()], [
       ['a', '1,2'],
       ['b', '3,4'],
       ['c', '5']
@@ -322,7 +322,7 @@ tap.test('Headers as Iterable', t => {
     const order = []
     for (const [key] of headers) {
       order.push(key)
-      headers.set(key + key, 1)
+      headers.append(key + key, 1)
     }
 
     t.strictSame(order, ['x', 'y', 'z'])
@@ -444,7 +444,7 @@ tap.test('Headers as Iterable', t => {
     headers.append('c', '7')
     headers.append('abc', '8')
 
-    const expected = new Map([
+    const expected = [...new Map([
       ['a', '1'],
       ['abc', '8'],
       ['b', '2'],
@@ -452,45 +452,9 @@ tap.test('Headers as Iterable', t => {
       ['d', '4'],
       ['e', '5'],
       ['f', '6']
-    ])
-
-    t.same(headers[kHeadersList], expected)
-  })
-})
+    ])]
 
-tap.test('binary search', t => {
-  //           0   1   2   3   4   5   6   7
-  const l1 = ['b', 1, 'c', 2, 'd', 3, 'f', 4]
-  //           0   1   2   3   4   5   6   7   8   9
-  const l2 = ['b', 1, 'c', 2, 'd', 3, 'e', 4, 'g', 5]
-  //           0   1   2   3    4    5   6   7
-  const l3 = ['a', 1, 'b', 2, 'bcd', 3, 'c', 4]
-  //           0   1   2   3   4   5    6    7   8   9
-  const l4 = ['a', 1, 'b', 2, 'c', 3, 'cde', 4, 'f', 5]
-
-  const tests = [
-    { input: [l1, 'c'], expected: 2, message: 'find item in n=even array' },
-    { input: [l1, 'f'], expected: 6, message: 'find item at end of n=even array' },
-    { input: [l1, 'b'], expected: 0, message: 'find item at beg of n=even array' },
-    { input: [l1, 'e'], expected: 6, message: 'find new item position in n=even array' },
-    { input: [l1, 'g'], expected: 8, message: 'find new item position at end of n=even array' },
-    { input: [l1, 'a'], expected: 0, message: 'find new item position at beg of n=even array' },
-    { input: [l2, 'c'], expected: 2, message: 'find item in n=odd array' },
-    { input: [l2, 'g'], expected: 8, message: 'find item at end of n=odd array' },
-    { input: [l2, 'b'], expected: 0, message: 'find item at beg of n=odd array' },
-    { input: [l2, 'f'], expected: 8, message: 'find new item position in n=odd array' },
-    { input: [l2, 'h'], expected: 10, message: 'find new item position at end of n=odd array' },
-    { input: [l2, 'a'], expected: 0, message: 'find new item position at beg of n=odd array' },
-    { input: [l3, 'b'], expected: 2, message: 'find item with similarity in n=odd array' },
-    { input: [l3, 'bcd'], expected: 4, message: 'find item with similarity in n=odd array' },
-    { input: [l4, 'c'], expected: 4, message: 'find item with similarity in n=odd array' },
-    { input: [l4, 'cde'], expected: 6, message: 'find item with similarity in n=odd array' }
-  ]
-
-  t.plan(tests.length)
-
-  tests.forEach(({ input: [list, target], expected, message }) => {
-    t.equal(expected, binarySearch(list, target), message)
+    t.same([...headers[kHeadersList]], expected)
   })
 })
 
@@ -602,7 +566,10 @@ tap.test('node inspect', (t) => {
   const headers = new Headers()
   headers.set('k1', 'v1')
   headers.set('k2', 'v2')
-  t.equal(util.inspect(headers), "HeadersList(2) [Map] { 'k1' => 'v1', 'k2' => 'v2' }")
+  t.equal(util.inspect(headers), `HeadersList {
+  [Symbol(headers map)]: Map(2) { 'k1' => 'v1', 'k2' => 'v2' },
+  [Symbol(headers map sorted)]: false
+}`)
   t.end()
 })
 

From 61b613d977711928606410a916524eaeab14ca13 Mon Sep 17 00:00:00 2001
From: RafaelGSS <rafael.nunu@hotmail.com>
Date: Thu, 7 Apr 2022 23:49:27 -0300
Subject: [PATCH 05/12] perf: use headersList.set to bypass validation

---
 lib/fetch/index.js      | 16 ++++++++--------
 lib/fetch/request.js    |  1 +
 lib/fetch/response.js   |  2 +-
 test/node-fetch/mock.js |  5 ++---
 4 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/lib/fetch/index.js b/lib/fetch/index.js
index 9da2680a49b..5ccc5c14e92 100644
--- a/lib/fetch/index.js
+++ b/lib/fetch/index.js
@@ -1334,7 +1334,7 @@ async function httpNetworkOrCacheFetch (
   //    user agents should append `User-Agent`/default `User-Agent` value to
   //    httpRequest’s header list.
   if (!httpRequest.headersList.has('user-agent')) {
-    httpRequest.headersList.append('user-agent', 'undici')
+    httpRequest.headersList.set('user-agent', 'undici')
   }
 
   //    15. If httpRequest’s cache mode is "default" and httpRequest’s header
@@ -1361,7 +1361,7 @@ async function httpNetworkOrCacheFetch (
     !httpRequest.preventNoCacheCacheControlHeaderModification &&
     !httpRequest.headersList.has('cache-control')
   ) {
-    httpRequest.headersList.append('cache-control', 'max-age=0')
+    httpRequest.headersList.set('cache-control', 'max-age=0')
   }
 
   //    17. If httpRequest’s cache mode is "no-store" or "reload", then:
@@ -1369,20 +1369,20 @@ async function httpNetworkOrCacheFetch (
     // 1. If httpRequest’s header list does not contain `Pragma`, then append
     // `Pragma`/`no-cache` to httpRequest’s header list.
     if (!httpRequest.headersList.has('pragma')) {
-      httpRequest.headersList.append('pragma', 'no-cache')
+      httpRequest.headersList.set('pragma', 'no-cache')
     }
 
     // 2. If httpRequest’s header list does not contain `Cache-Control`,
     // then append `Cache-Control`/`no-cache` to httpRequest’s header list.
     if (!httpRequest.headersList.has('cache-control')) {
-      httpRequest.headersList.append('cache-control', 'no-cache')
+      httpRequest.headersList.set('cache-control', 'no-cache')
     }
   }
 
   //    18. If httpRequest’s header list contains `Range`, then append
   //    `Accept-Encoding`/`identity` to httpRequest’s header list.
   if (httpRequest.headersList.has('range')) {
-    httpRequest.headersList.append('accept-encoding', 'identity')
+    httpRequest.headersList.set('accept-encoding', 'identity')
   }
 
   //    19. Modify httpRequest’s header list per HTTP. Do not append a given
@@ -1390,9 +1390,9 @@ async function httpNetworkOrCacheFetch (
   //    TODO: https://github.com/whatwg/fetch/issues/1285#issuecomment-896560129
   if (!httpRequest.headersList.has('accept-encoding')) {
     if (/^https:/.test(requestCurrentURL(httpRequest).protocol)) {
-      httpRequest.headersList.append('accept-encoding', 'br, gzip, deflate')
+      httpRequest.headersList.set('accept-encoding', 'br, gzip, deflate')
     } else {
-      httpRequest.headersList.append('accept-encoding', 'gzip, deflate')
+      httpRequest.headersList.set('accept-encoding', 'gzip, deflate')
     }
   }
 
@@ -1918,7 +1918,7 @@ async function httpNetworkFetch (
         origin: url.origin,
         method: request.method,
         body: fetchParams.controller.dispatcher[kIsMockActive] ? request.body && request.body.source : body,
-        headers: request.headersList,
+        headers: [...request.headersList].flat(),
         maxRedirections: 0
       },
       {
diff --git a/lib/fetch/request.js b/lib/fetch/request.js
index 93175d20eed..8e16d9299ec 100644
--- a/lib/fetch/request.js
+++ b/lib/fetch/request.js
@@ -464,6 +464,7 @@ class Request {
       // this’s headers.
       if (contentType && !this[kHeaders].has('content-type')) {
         this[kHeaders].append('content-type', contentType)
+        this[kState].headersList.append('content-type', contentType)
       }
     }
 
diff --git a/lib/fetch/response.js b/lib/fetch/response.js
index 3ecd28980eb..0e96c4497c8 100644
--- a/lib/fetch/response.js
+++ b/lib/fetch/response.js
@@ -81,7 +81,7 @@ class Response {
     const value = parsedURL.toString()
 
     // 7. Append `Location`/value to responseObject’s response’s header list.
-    responseObject[kState].headersList.push('location', value)
+    responseObject[kState].headersList.append('location', value)
 
     // 8. Return responseObject.
     return responseObject
diff --git a/test/node-fetch/mock.js b/test/node-fetch/mock.js
index d4881eabc35..a53f464a1a9 100644
--- a/test/node-fetch/mock.js
+++ b/test/node-fetch/mock.js
@@ -68,8 +68,8 @@ describe('node-fetch with MockAgent', () => {
       .intercept({
         path: '/test',
         method: 'GET',
-        headers: {
-          'User-Agent': /^undici$/
+        headers: (h) => {
+          return h['user-agent'] === 'undici'
         }
       })
       .reply(200, { success: true })
@@ -79,7 +79,6 @@ describe('node-fetch with MockAgent', () => {
       method: 'GET',
       headers: new Headers({ 'User-Agent': 'undici' })
     })
-
     expect(res.status).to.equal(200)
     expect(await res.json()).to.deep.equal({ success: true })
   })

From 2986c982d6681d70a2ea4a6e0173d31d93824844 Mon Sep 17 00:00:00 2001
From: RafaelGSS <rafael.nunu@hotmail.com>
Date: Thu, 7 Apr 2022 23:55:40 -0300
Subject: [PATCH 06/12] update: remove comment

---
 lib/fetch/request.js | 1 -
 1 file changed, 1 deletion(-)

diff --git a/lib/fetch/request.js b/lib/fetch/request.js
index 8e16d9299ec..845344a7f9c 100644
--- a/lib/fetch/request.js
+++ b/lib/fetch/request.js
@@ -426,7 +426,6 @@ class Request {
         ])
       } else {
         // 5. Otherwise, fill this’s headers with headers.
-        // TODO: check it before merge
         fillHeaders(this[kState].headersList, headers)
       }
     }

From 0941bb5e01475d4a440de53fa1cf4cfcadb9b03b Mon Sep 17 00:00:00 2001
From: RafaelGSS <rafael.nunu@hotmail.com>
Date: Thu, 7 Apr 2022 23:57:54 -0300
Subject: [PATCH 07/12] fix: lint

---
 lib/fetch/headers.js | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/lib/fetch/headers.js b/lib/fetch/headers.js
index a4294dafee8..513dcf8a6b2 100644
--- a/lib/fetch/headers.js
+++ b/lib/fetch/headers.js
@@ -78,7 +78,7 @@ function fill (headers, object) {
 }
 
 class HeadersList {
-  constructor(init) {
+  constructor (init) {
     if (init instanceof HeadersList) {
       this[kHeadersMap] = new Map(init[kHeadersMap])
       this[kSorted] = init[kSorted]
@@ -117,7 +117,7 @@ class HeadersList {
     return this[kHeadersMap].has(normalizedName)
   }
 
-  sortMap() {
+  sortMap () {
     this[kHeadersMap] = new Map([...this[kHeadersMap]].sort((a, b) => a[0] < b[0] ? -1 : 1))
     this[kSorted] = true
   }
@@ -127,7 +127,7 @@ class HeadersList {
     return this[kHeadersMap].set(key, val)
   }
 
-  *[Symbol.iterator]() {
+  * [Symbol.iterator] () {
     if (!this[kSorted]) {
       this.sortMap()
     }
@@ -299,7 +299,7 @@ class Headers {
 
   // The value pairs to iterate over are the return value of running sort
   // and combine with this’s header list.
-  _getHeadersListIterable() {
+  _getHeadersListIterable () {
     if (!this[kHeadersList][kSorted]) {
       this[kHeadersList].sortMap()
     }

From aceec4d3358505c3ae77cbd4c9ba250d55f09b3d Mon Sep 17 00:00:00 2001
From: RafaelGSS <rafael.nunu@hotmail.com>
Date: Fri, 8 Apr 2022 11:19:16 -0300
Subject: [PATCH 08/12] update(headers): create a new headers map for sorting

---
 lib/fetch/headers.js  | 28 ++++++++++++++++------------
 lib/fetch/index.js    | 12 ++++++------
 test/fetch/headers.js |  3 ++-
 3 files changed, 24 insertions(+), 19 deletions(-)

diff --git a/lib/fetch/headers.js b/lib/fetch/headers.js
index 513dcf8a6b2..376c879b088 100644
--- a/lib/fetch/headers.js
+++ b/lib/fetch/headers.js
@@ -12,7 +12,8 @@ const {
 } = require('./constants')
 
 const kHeadersMap = Symbol('headers map')
-const kSorted = Symbol('headers map sorted')
+const kSorted = Symbol('kSorted')
+const kHeadersSortedMap = Symbol('headers map sorted')
 
 function normalizeAndValidateHeaderName (name) {
   if (name === undefined) {
@@ -82,9 +83,11 @@ class HeadersList {
     if (init instanceof HeadersList) {
       this[kHeadersMap] = new Map(init[kHeadersMap])
       this[kSorted] = init[kSorted]
+      this[kHeadersSortedMap] = init[kHeadersSortedMap]
     } else {
       this[kHeadersMap] = new Map(init)
       this[kSorted] = false
+      this[kHeadersSortedMap] = new Map()
     }
   }
 
@@ -118,12 +121,13 @@ class HeadersList {
   }
 
   sortMap () {
-    this[kHeadersMap] = new Map([...this[kHeadersMap]].sort((a, b) => a[0] < b[0] ? -1 : 1))
+    this[kHeadersSortedMap] = new Map([...this[kHeadersMap]].sort((a, b) => a[0] < b[0] ? -1 : 1))
     this[kSorted] = true
   }
 
   // bypass normalization
   set (key, val) {
+    this[kSorted] = false
     return this[kHeadersMap].set(key, val)
   }
 
@@ -132,7 +136,7 @@ class HeadersList {
       this.sortMap()
     }
 
-    for (const [key, val] of this[kHeadersMap].entries()) {
+    for (const [key, val] of this[kHeadersSortedMap].entries()) {
       yield [key, val]
     }
   }
@@ -304,26 +308,26 @@ class Headers {
       this[kHeadersList].sortMap()
     }
 
-    return new HeadersList(this[kHeadersList])
+    return this[kHeadersList][kHeadersSortedMap]
   }
 
   * keys () {
-    const listFreezed = this._getHeadersListIterable()
-    for (const key of listFreezed[kHeadersMap].keys()) {
+    const sortedHeaders = this._getHeadersListIterable()
+    for (const key of sortedHeaders.keys()) {
       yield key
     }
   }
 
   * values () {
-    const listFreezed = this._getHeadersListIterable()
-    for (const val of listFreezed[kHeadersMap].values()) {
+    const sortedHeaders = this._getHeadersListIterable()
+    for (const val of sortedHeaders.values()) {
       yield val
     }
   }
 
   * entries () {
-    const listFreezed = this._getHeadersListIterable()
-    for (const [key, val] of listFreezed[kHeadersMap]) {
+    const sortedHeaders = this._getHeadersListIterable()
+    for (const [key, val] of sortedHeaders) {
       yield [key, val]
     }
   }
@@ -345,8 +349,8 @@ class Headers {
     const callback = args[0]
     const thisArg = args[1]
 
-    const listFreezed = this._getHeadersListIterable()
-    listFreezed[kHeadersMap].forEach((value, index) => {
+    const sortedHeaders = this._getHeadersListIterable()
+    sortedHeaders.forEach((value, index) => {
       callback.apply(thisArg, [value, index, this])
     })
   }
diff --git a/lib/fetch/index.js b/lib/fetch/index.js
index 5ccc5c14e92..11caab91d01 100644
--- a/lib/fetch/index.js
+++ b/lib/fetch/index.js
@@ -1361,7 +1361,7 @@ async function httpNetworkOrCacheFetch (
     !httpRequest.preventNoCacheCacheControlHeaderModification &&
     !httpRequest.headersList.has('cache-control')
   ) {
-    httpRequest.headersList.set('cache-control', 'max-age=0')
+    httpRequest.headersList.append('cache-control', 'max-age=0')
   }
 
   //    17. If httpRequest’s cache mode is "no-store" or "reload", then:
@@ -1369,20 +1369,20 @@ async function httpNetworkOrCacheFetch (
     // 1. If httpRequest’s header list does not contain `Pragma`, then append
     // `Pragma`/`no-cache` to httpRequest’s header list.
     if (!httpRequest.headersList.has('pragma')) {
-      httpRequest.headersList.set('pragma', 'no-cache')
+      httpRequest.headersList.append('pragma', 'no-cache')
     }
 
     // 2. If httpRequest’s header list does not contain `Cache-Control`,
     // then append `Cache-Control`/`no-cache` to httpRequest’s header list.
     if (!httpRequest.headersList.has('cache-control')) {
-      httpRequest.headersList.set('cache-control', 'no-cache')
+      httpRequest.headersList.append('cache-control', 'no-cache')
     }
   }
 
   //    18. If httpRequest’s header list contains `Range`, then append
   //    `Accept-Encoding`/`identity` to httpRequest’s header list.
   if (httpRequest.headersList.has('range')) {
-    httpRequest.headersList.set('accept-encoding', 'identity')
+    httpRequest.headersList.append('accept-encoding', 'identity')
   }
 
   //    19. Modify httpRequest’s header list per HTTP. Do not append a given
@@ -1390,9 +1390,9 @@ async function httpNetworkOrCacheFetch (
   //    TODO: https://github.com/whatwg/fetch/issues/1285#issuecomment-896560129
   if (!httpRequest.headersList.has('accept-encoding')) {
     if (/^https:/.test(requestCurrentURL(httpRequest).protocol)) {
-      httpRequest.headersList.set('accept-encoding', 'br, gzip, deflate')
+      httpRequest.headersList.append('accept-encoding', 'br, gzip, deflate')
     } else {
-      httpRequest.headersList.set('accept-encoding', 'gzip, deflate')
+      httpRequest.headersList.append('accept-encoding', 'gzip, deflate')
     }
   }
 
diff --git a/test/fetch/headers.js b/test/fetch/headers.js
index 38f52c577bc..cf5bdbfe1aa 100644
--- a/test/fetch/headers.js
+++ b/test/fetch/headers.js
@@ -568,7 +568,8 @@ tap.test('node inspect', (t) => {
   headers.set('k2', 'v2')
   t.equal(util.inspect(headers), `HeadersList {
   [Symbol(headers map)]: Map(2) { 'k1' => 'v1', 'k2' => 'v2' },
-  [Symbol(headers map sorted)]: false
+  [Symbol(kSorted)]: false,
+  [Symbol(headers map sorted)]: Map(0) {}
 }`)
   t.end()
 })

From 765fc314ca9d620da54955ec5548b138bedc85e3 Mon Sep 17 00:00:00 2001
From: RafaelGSS <rafael.nunu@hotmail.com>
Date: Fri, 8 Apr 2022 11:32:10 -0300
Subject: [PATCH 09/12] update: remove kSorted

---
 lib/fetch/headers.js  | 14 +++++---------
 test/fetch/headers.js |  3 +--
 2 files changed, 6 insertions(+), 11 deletions(-)

diff --git a/lib/fetch/headers.js b/lib/fetch/headers.js
index 376c879b088..4666cf2e008 100644
--- a/lib/fetch/headers.js
+++ b/lib/fetch/headers.js
@@ -12,7 +12,6 @@ const {
 } = require('./constants')
 
 const kHeadersMap = Symbol('headers map')
-const kSorted = Symbol('kSorted')
 const kHeadersSortedMap = Symbol('headers map sorted')
 
 function normalizeAndValidateHeaderName (name) {
@@ -82,12 +81,10 @@ class HeadersList {
   constructor (init) {
     if (init instanceof HeadersList) {
       this[kHeadersMap] = new Map(init[kHeadersMap])
-      this[kSorted] = init[kSorted]
       this[kHeadersSortedMap] = init[kHeadersSortedMap]
     } else {
       this[kHeadersMap] = new Map(init)
-      this[kSorted] = false
-      this[kHeadersSortedMap] = new Map()
+      this[kHeadersSortedMap] = undefined
     }
   }
 
@@ -101,7 +98,7 @@ class HeadersList {
       this[kHeadersMap].set(normalizedName, `${exists}, ${normalizedValue}`)
     } else {
       this[kHeadersMap].set(normalizedName, `${normalizedValue}`)
-      this[kSorted] = false
+      this[kHeadersSortedMap] = undefined
     }
   }
 
@@ -122,17 +119,16 @@ class HeadersList {
 
   sortMap () {
     this[kHeadersSortedMap] = new Map([...this[kHeadersMap]].sort((a, b) => a[0] < b[0] ? -1 : 1))
-    this[kSorted] = true
   }
 
   // bypass normalization
   set (key, val) {
-    this[kSorted] = false
+    this[kHeadersSortedMap] = undefined
     return this[kHeadersMap].set(key, val)
   }
 
   * [Symbol.iterator] () {
-    if (!this[kSorted]) {
+    if (!this[kHeadersSortedMap]) {
       this.sortMap()
     }
 
@@ -304,7 +300,7 @@ class Headers {
   // The value pairs to iterate over are the return value of running sort
   // and combine with this’s header list.
   _getHeadersListIterable () {
-    if (!this[kHeadersList][kSorted]) {
+    if (!this[kHeadersList][kHeadersSortedMap]) {
       this[kHeadersList].sortMap()
     }
 
diff --git a/test/fetch/headers.js b/test/fetch/headers.js
index cf5bdbfe1aa..f10b2604713 100644
--- a/test/fetch/headers.js
+++ b/test/fetch/headers.js
@@ -568,8 +568,7 @@ tap.test('node inspect', (t) => {
   headers.set('k2', 'v2')
   t.equal(util.inspect(headers), `HeadersList {
   [Symbol(headers map)]: Map(2) { 'k1' => 'v1', 'k2' => 'v2' },
-  [Symbol(kSorted)]: false,
-  [Symbol(headers map sorted)]: Map(0) {}
+  [Symbol(headers map sorted)]: undefined
 }`)
   t.end()
 })

From 0fdf0a698b495d6148396a41ffd4682584203187 Mon Sep 17 00:00:00 2001
From: RafaelGSS <rafael.nunu@hotmail.com>
Date: Fri, 8 Apr 2022 19:58:02 -0300
Subject: [PATCH 10/12] update: replace .set to .append

---
 lib/fetch/index.js    | 2 +-
 lib/fetch/response.js | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/fetch/index.js b/lib/fetch/index.js
index 11caab91d01..9055d93b092 100644
--- a/lib/fetch/index.js
+++ b/lib/fetch/index.js
@@ -1334,7 +1334,7 @@ async function httpNetworkOrCacheFetch (
   //    user agents should append `User-Agent`/default `User-Agent` value to
   //    httpRequest’s header list.
   if (!httpRequest.headersList.has('user-agent')) {
-    httpRequest.headersList.set('user-agent', 'undici')
+    httpRequest.headersList.append('user-agent', 'undici')
   }
 
   //    15. If httpRequest’s cache mode is "default" and httpRequest’s header
diff --git a/lib/fetch/response.js b/lib/fetch/response.js
index 0e96c4497c8..f704ac87512 100644
--- a/lib/fetch/response.js
+++ b/lib/fetch/response.js
@@ -172,7 +172,7 @@ class Response {
       // not contain `Content-Type`, then append `Content-Type`/Content-Type
       // to this’s response’s header list.
       if (contentType && !this.headers.has('content-type')) {
-        this.headers.set('content-type', contentType)
+        this.headers.append('content-type', contentType)
       }
     }
   }

From 6065226e78fb462e007f35acb581e4e8d8255616 Mon Sep 17 00:00:00 2001
From: Robert Nagy <ronagy@icloud.com>
Date: Sat, 9 Apr 2022 11:55:01 +0200
Subject: [PATCH 11/12] fixes

---
 lib/fetch/headers.js  | 87 ++++++++++++++++++++++++-------------------
 lib/fetch/request.js  |  5 +++
 lib/fetch/response.js | 13 +++----
 test/fetch/headers.js | 15 +-------
 4 files changed, 59 insertions(+), 61 deletions(-)

diff --git a/lib/fetch/headers.js b/lib/fetch/headers.js
index 4666cf2e008..161555f94b8 100644
--- a/lib/fetch/headers.js
+++ b/lib/fetch/headers.js
@@ -84,11 +84,13 @@ class HeadersList {
       this[kHeadersSortedMap] = init[kHeadersSortedMap]
     } else {
       this[kHeadersMap] = new Map(init)
-      this[kHeadersSortedMap] = undefined
+      this[kHeadersSortedMap] = null
     }
   }
 
   append (name, value) {
+    this[kHeadersSortedMap] = null
+
     const normalizedName = normalizeAndValidateHeaderName(name)
     const normalizedValue = normalizeAndValidateHeaderValue(name, value)
 
@@ -98,11 +100,19 @@ class HeadersList {
       this[kHeadersMap].set(normalizedName, `${exists}, ${normalizedValue}`)
     } else {
       this[kHeadersMap].set(normalizedName, `${normalizedValue}`)
-      this[kHeadersSortedMap] = undefined
     }
   }
 
+  set (name, value) {
+    this[kHeadersSortedMap] = null
+
+    const normalizedName = normalizeAndValidateHeaderName(name)
+    return this[kHeadersMap].set(normalizedName, value)
+  }
+
   delete (name) {
+    this[kHeadersSortedMap] = null
+
     const normalizedName = normalizeAndValidateHeaderName(name)
     return this[kHeadersMap].delete(normalizedName)
   }
@@ -117,24 +127,20 @@ class HeadersList {
     return this[kHeadersMap].has(normalizedName)
   }
 
-  sortMap () {
-    this[kHeadersSortedMap] = new Map([...this[kHeadersMap]].sort((a, b) => a[0] < b[0] ? -1 : 1))
+  keys() {
+    return this[kHeadersMap].keys()
   }
 
-  // bypass normalization
-  set (key, val) {
-    this[kHeadersSortedMap] = undefined
-    return this[kHeadersMap].set(key, val)
+  values () {
+    return this[kHeadersMap].values()
   }
 
-  * [Symbol.iterator] () {
-    if (!this[kHeadersSortedMap]) {
-      this.sortMap()
-    }
+  entries () {
+    return this[kHeadersMap].entries()
+  }
 
-    for (const [key, val] of this[kHeadersSortedMap].entries()) {
-      yield [key, val]
-    }
+  [Symbol.iterator] () {
+    return this[kHeadersMap][Symbol.iterator]()
   }
 }
 
@@ -276,20 +282,18 @@ class Headers {
       )
     }
 
-    const normalizedName = normalizeAndValidateHeaderName(String(args[0]))
-
     if (this[kGuard] === 'immutable') {
       throw new TypeError('immutable')
     } else if (
       this[kGuard] === 'request' &&
-      forbiddenHeaderNames.includes(normalizedName)
+      forbiddenHeaderNames.includes(String(args[0]).toLocaleLowerCase())
     ) {
       return
     } else if (this[kGuard] === 'request-no-cors') {
       // TODO
     } else if (
       this[kGuard] === 'response' &&
-      forbiddenResponseHeaderNames.includes(normalizedName)
+      forbiddenResponseHeaderNames.includes(String(args[0]).toLocaleLowerCase())
     ) {
       return
     }
@@ -297,35 +301,41 @@ class Headers {
     return this[kHeadersList].set(String(args[0]), String(args[1]))
   }
 
-  // The value pairs to iterate over are the return value of running sort
-  // and combine with this’s header list.
-  _getHeadersListIterable () {
-    if (!this[kHeadersList][kHeadersSortedMap]) {
-      this[kHeadersList].sortMap()
+  get [kHeadersSortedMap] () {
+    this[kHeadersList][kHeadersSortedMap] ??= new Map([...this[kHeadersList]].sort((a, b) => a[0] < b[0] ? -1 : 1))
+    return this[kHeadersList][kHeadersSortedMap]
+  }
+
+  keys () {
+    if (!(this instanceof Headers)) {
+      throw new TypeError('Illegal invocation')
     }
 
-    return this[kHeadersList][kHeadersSortedMap]
+    return this[kHeadersSortedMap].keys()
   }
 
-  * keys () {
-    const sortedHeaders = this._getHeadersListIterable()
-    for (const key of sortedHeaders.keys()) {
-      yield key
+  values () {
+    if (!(this instanceof Headers)) {
+      throw new TypeError('Illegal invocation')
     }
+
+    return this[kHeadersSortedMap].values()
   }
 
-  * values () {
-    const sortedHeaders = this._getHeadersListIterable()
-    for (const val of sortedHeaders.values()) {
-      yield val
+  entries () {
+    if (!(this instanceof Headers)) {
+      throw new TypeError('Illegal invocation')
     }
+
+    return this[kHeadersSortedMap].entries()
   }
 
-  * entries () {
-    const sortedHeaders = this._getHeadersListIterable()
-    for (const [key, val] of sortedHeaders) {
-      yield [key, val]
+  [Symbol.iterator] () {
+    if (!(this instanceof Headers)) {
+      throw new TypeError('Illegal invocation')
     }
+
+    return this[kHeadersSortedMap]
   }
 
   forEach (...args) {
@@ -345,8 +355,7 @@ class Headers {
     const callback = args[0]
     const thisArg = args[1]
 
-    const sortedHeaders = this._getHeadersListIterable()
-    sortedHeaders.forEach((value, index) => {
+    this[kHeadersSortedMap].forEach((value, index) => {
       callback.apply(thisArg, [value, index, this])
     })
   }
diff --git a/lib/fetch/request.js b/lib/fetch/request.js
index 845344a7f9c..0f10e678894 100644
--- a/lib/fetch/request.js
+++ b/lib/fetch/request.js
@@ -420,6 +420,11 @@ class Request {
       // 4. If headers is a Headers object, then for each header in its header
       // list, append header’s name/header’s value to this’s headers.
       if (headers instanceof Headers) {
+        // TODO (fix): Why doesn't this work?
+        // for (const [key, val] of headers[kHeadersList]) {
+        //   this[kHeaders].append(key, val)
+        // }
+
         this[kState].headersList = new HeadersList([
           ...this[kState].headersList,
           ...headers[kHeadersList]
diff --git a/lib/fetch/response.js b/lib/fetch/response.js
index f704ac87512..d1ce6ce95bd 100644
--- a/lib/fetch/response.js
+++ b/lib/fetch/response.js
@@ -394,16 +394,13 @@ function makeFilteredHeadersList (headersList, filter) {
       // Override methods used by Headers class.
       if (prop === 'get' || prop === 'has') {
         return (name) => filter(name) ? target[prop](name) : undefined
-      } else if (prop === 'slice') {
-        return (...args) => {
-          assert(args.length === 0)
-          const arr = []
-          for (let index = 0; index < target.length; index += 2) {
-            if (filter(target[index])) {
-              arr.push(target[index], target[index + 1])
+      } else if (prop === Symbol.iterator) {
+        return function * () {
+          for (const entry of target) {
+            if (filter(entry[0])) {
+              yield entry
             }
           }
-          return arr
         }
       } else {
         return target[prop]
diff --git a/test/fetch/headers.js b/test/fetch/headers.js
index f10b2604713..4c4e2171915 100644
--- a/test/fetch/headers.js
+++ b/test/fetch/headers.js
@@ -1,6 +1,5 @@
 'use strict'
 
-const util = require('util')
 const tap = require('tap')
 const {
   Headers,
@@ -8,7 +7,6 @@ const {
   normalizeAndValidateHeaderValue,
   fill
 } = require('../../lib/fetch/headers')
-const { kHeadersList } = require('../../lib/core/symbols')
 const { kGuard } = require('../../lib/fetch/symbols')
 const {
   forbiddenHeaderNames,
@@ -454,7 +452,7 @@ tap.test('Headers as Iterable', t => {
       ['f', '6']
     ])]
 
-    t.same([...headers[kHeadersList]], expected)
+    t.same([...headers], expected)
   })
 })
 
@@ -562,17 +560,6 @@ tap.test('various init paths of Headers', (t) => {
   t.end()
 })
 
-tap.test('node inspect', (t) => {
-  const headers = new Headers()
-  headers.set('k1', 'v1')
-  headers.set('k2', 'v2')
-  t.equal(util.inspect(headers), `HeadersList {
-  [Symbol(headers map)]: Map(2) { 'k1' => 'v1', 'k2' => 'v2' },
-  [Symbol(headers map sorted)]: undefined
-}`)
-  t.end()
-})
-
 tap.test('immutable guard', (t) => {
   const headers = new Headers()
   headers.set('key', 'val')

From f604e28667a798102e33c1147b9402801e1b7653 Mon Sep 17 00:00:00 2001
From: RafaelGSS <rafael.nunu@hotmail.com>
Date: Sat, 9 Apr 2022 10:03:44 -0300
Subject: [PATCH 12/12] fix: lint

---
 lib/fetch/headers.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/fetch/headers.js b/lib/fetch/headers.js
index 161555f94b8..e0295be2250 100644
--- a/lib/fetch/headers.js
+++ b/lib/fetch/headers.js
@@ -127,7 +127,7 @@ class HeadersList {
     return this[kHeadersMap].has(normalizedName)
   }
 
-  keys() {
+  keys () {
     return this[kHeadersMap].keys()
   }