From 87fa73498d6014a33989179cfaa4347dcb29600f Mon Sep 17 00:00:00 2001
From: Khafra <maitken033380023@gmail.com>
Date: Thu, 9 Feb 2023 00:15:58 -0500
Subject: [PATCH] fix(headers): clone getSetCookie list & add getSetCookie type
 (#1917)

---
 lib/fetch/headers.js       |  8 +++++++-
 test/fetch/headers.js      | 18 ++++++++++++++++++
 test/types/fetch.test-d.ts |  4 +++-
 types/fetch.d.ts           |  1 +
 4 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/lib/fetch/headers.js b/lib/fetch/headers.js
index af2c64bad8d..634b81fc74a 100644
--- a/lib/fetch/headers.js
+++ b/lib/fetch/headers.js
@@ -392,7 +392,13 @@ class Headers {
     // 2. Return the values of all headers in this’s header list whose name is
     //    a byte-case-insensitive match for `Set-Cookie`, in order.
 
-    return this[kHeadersList].cookies ?? []
+    const list = this[kHeadersList].cookies
+
+    if (list) {
+      return [...list]
+    }
+
+    return []
   }
 
   // https://fetch.spec.whatwg.org/#concept-header-list-sort-and-combine
diff --git a/test/fetch/headers.js b/test/fetch/headers.js
index f4508d01fd9..7ae85b815b5 100644
--- a/test/fetch/headers.js
+++ b/test/fetch/headers.js
@@ -665,3 +665,21 @@ tap.test('invalid headers', (t) => {
 
   t.end()
 })
+
+tap.test('Headers.prototype.getSetCookie', (t) => {
+  t.test('Mutating the returned list does not affect the set-cookie list', (t) => {
+    const h = new Headers([
+      ['set-cookie', 'a=b'],
+      ['set-cookie', 'c=d']
+    ])
+
+    const old = h.getSetCookie()
+    h.getSetCookie().push('oh=no')
+    const now = h.getSetCookie()
+
+    t.same(old, now)
+    t.end()
+  })
+
+  t.end()
+})
diff --git a/test/types/fetch.test-d.ts b/test/types/fetch.test-d.ts
index a76d6d7043c..e11296aa85c 100644
--- a/test/types/fetch.test-d.ts
+++ b/test/types/fetch.test-d.ts
@@ -168,4 +168,6 @@ expectType<Response>(response.clone())
 
 expectType<Request>(new Request('https://example.com', { body: 'Hello, world', duplex: 'half' }))
 expectAssignable<RequestInit>({ duplex: 'half' })
-expectNotAssignable<RequestInit>({ duplex: 'not valid' })
\ No newline at end of file
+expectNotAssignable<RequestInit>({ duplex: 'not valid' })
+
+expectType<string[]>(headers.getSetCookie())
diff --git a/types/fetch.d.ts b/types/fetch.d.ts
index 58bd4d2a769..fa4619c9182 100644
--- a/types/fetch.d.ts
+++ b/types/fetch.d.ts
@@ -59,6 +59,7 @@ export declare class Headers implements SpecIterable<[string, string]> {
   readonly get: (name: string) => string | null
   readonly has: (name: string) => boolean
   readonly set: (name: string, value: string) => void
+  readonly getSetCookie: () => string[]
   readonly forEach: (
     callbackfn: (value: string, key: string, iterable: Headers) => void,
     thisArg?: unknown