Fix types, pull in middleware header fix from next.js

Next js PR w/ the header fix:
vercel/next.js#30560

packages/middleware/src/websandbox/adapter.ts

@@ -5,6 +5,7 @@ import { NextFetchEvent } from './spec-extension/fetch-event';
 import { NextRequest, RequestInit } from './spec-extension/request';
 import { SpecResponse } from './spec-extension/response';
 import { waitUntilSymbol } from './spec-compliant/fetch-event';
+import { Response } from 'node-fetch';
 
 export async function adapter(params: {
   handler: (request: NextRequest, event: NextFetchEvent) => Promise<Response>;

packages/middleware/src/websandbox/types.ts

@@ -1,3 +1,5 @@
+import { Response } from 'node-fetch';
+
 export interface NodeHeaders {
   [header: string]: string | string[] | undefined;
 }

packages/middleware/src/websandbox/utils.ts

@@ -40,9 +40,85 @@ export function toNodeHeaders(headers?: Headers): NodeHeaders {
     for (const [key, value] of headers.entries()) {
       result[key] = value;
       if (key.toLowerCase() === 'set-cookie') {
-        result[key] = value.split(', ');
+        result[key] = splitCookiesString(value);
       }
     }
   }
   return result;
 }
+
+/*
+  Set-Cookie header field-values are sometimes comma joined in one string. This splits them without choking on commas
+  that are within a single set-cookie field-value, such as in the Expires portion.
+  This is uncommon, but explicitly allowed - see https://tools.ietf.org/html/rfc2616#section-4.2
+  Node.js does this for every header *except* set-cookie - see https://github.com/nodejs/node/blob/d5e363b77ebaf1caf67cd7528224b651c86815c1/lib/_http_incoming.js#L128
+  React Native's fetch does this for *every* header, including set-cookie.
+  
+  Based on: https://github.com/google/j2objc/commit/16820fdbc8f76ca0c33472810ce0cb03d20efe25
+  Credits to: https://github.com/tomball for original and https://github.com/chrusart for JavaScript implementation
+*/
+export function splitCookiesString(cookiesString: string) {
+  const cookiesStrings = [];
+  let pos = 0;
+  let start;
+  let ch;
+  let lastComma;
+  let nextStart;
+  let cookiesSeparatorFound;
+
+  function skipWhitespace() {
+    while (pos < cookiesString.length && /\s/.test(cookiesString.charAt(pos))) {
+      pos += 1;
+    }
+    return pos < cookiesString.length;
+  }
+
+  function notSpecialChar() {
+    ch = cookiesString.charAt(pos);
+
+    return ch !== '=' && ch !== ';' && ch !== ',';
+  }
+
+  while (pos < cookiesString.length) {
+    start = pos;
+    cookiesSeparatorFound = false;
+
+    while (skipWhitespace()) {
+      ch = cookiesString.charAt(pos);
+      if (ch === ',') {
+        // ',' is a cookie separator if we have later first '=', not ';' or ','
+        lastComma = pos;
+        pos += 1;
+
+        skipWhitespace();
+        nextStart = pos;
+
+        while (pos < cookiesString.length && notSpecialChar()) {
+          pos += 1;
+        }
+
+        // currently special character
+        if (pos < cookiesString.length && cookiesString.charAt(pos) === '=') {
+          // we found cookies separator
+          cookiesSeparatorFound = true;
+          // pos is inside the next cookie, so back up and return it.
+          pos = nextStart;
+          cookiesStrings.push(cookiesString.substring(start, lastComma));
+          start = pos;
+        } else {
+          // in param ',' or param separator ';',
+          // we continue from that comma
+          pos = lastComma + 1;
+        }
+      } else {
+        pos += 1;
+      }
+    }
+
+    if (!cookiesSeparatorFound || pos >= cookiesString.length) {
+      cookiesStrings.push(cookiesString.substring(start, cookiesString.length));
+    }
+  }
+
+  return cookiesStrings;
+}

packages/middleware/tsconfig.json

@@ -2,7 +2,7 @@
   "compilerOptions": {
     "strict": true,
     "esModuleInterop": true,
-    "lib": ["esnext", "dom"],
+    "lib": ["esnext", "dom", "dom.iterable"],
     "target": "es2018",
     "module": "commonjs",
     "outDir": "dist",