Populate rawHeaders on Node.js HTTP client responses

src/node/internal/internal_http_incoming.ts

@@ -180,12 +180,16 @@ export class IncomingMessage extends Readable implements _IncomingMessage {
   #setFetchResponse(response: Response): void {
     this[kHeaders] = {};
     this[kHeadersDistinct] = {};
-    for (const header of response.headers.keys()) {
-      const value = response.headers.get(header) as string;
-      this[kHeaders][header] = value;
-      this[kHeadersDistinct][header] = [value];
-      this[kHeadersCount]++;
+    this.rawHeaders = [];
+
+    // Fetch only exposes displayed headers here, so rawHeaders mirrors the
+    // lower-cased/combined header view that the client can observe.
+    for (const [header, value] of response.headers) {
+      this.rawHeaders.push(header, value);
+      this._addHeaderLine(header, value, this[kHeaders]);
+      this._addHeaderLineDistinct(header, value, this[kHeadersDistinct]);
     }
+    this[kHeadersCount] = this.rawHeaders.length;
 
     this.#response = response;
     this._readableState.readingMore = true;

src/workerd/api/node/tests/http-client-nodejs-server.js

@@ -101,6 +101,15 @@ const helloWorldServer = http.createServer((req, res) => {
       break;
     }
 
+    case 'set-cookie-duplicates': {
+      res.writeHead(200, {
+        'Content-Type': 'text/plain',
+        'Set-Cookie': ['a=1', 'b=2'],
+      });
+      res.end('ok');
+      break;
+    }
+
     case 'echo': {
       // Echo the request body back as the response
       let body = '';

src/workerd/api/node/tests/http-client-nodejs-test.js

@@ -361,6 +361,8 @@ export const testHttpRequestHostHeader = {
       (res) => {
         strictEqual(res.statusCode, 400);
         strictEqual(res.headers.connection, 'close');
+        deepStrictEqual(res.rawHeaders, ['connection', 'close']);
+        deepStrictEqual(res.headersDistinct.connection, ['close']);
         resolve();
       }
     );
@@ -412,6 +414,97 @@ export const testHttpRequestJoinAuthorizationHeaders = {
   },
 };
 
+export const testHttpClientResponseRawHeaders = {
+  async test(_ctrl, env) {
+    const { promise, resolve } = Promise.withResolvers();
+    http.get(
+      {
+        hostname: env.SIDECAR_HOSTNAME,
+        port: env.HELLO_WORLD_SERVER_PORT,
+        method: 'POST',
+        headers: [
+          'authorization',
+          '1',
+          'authorization',
+          '2',
+          'cookie',
+          'foo',
+          'cookie',
+          'bar',
+        ],
+        joinDuplicateHeaders: true,
+        path: '/join-duplicate-headers',
+      },
+      (res) => {
+        strictEqual(res.statusCode, 200);
+        strictEqual(res.headers.authorization, '3, 4');
+        strictEqual(res.headers.cookie, 'foo; bar');
+        deepStrictEqual(res.rawHeaders, [
+          'authorization',
+          '3, 4',
+          'connection',
+          'keep-alive',
+          'cookie',
+          'foo; bar',
+          'keep-alive',
+          'timeout=1',
+          'transfer-encoding',
+          'chunked',
+        ]);
+        resolve();
+      }
+    );
+    await promise;
+  },
+};
+
+function getRawHeaderValues(rawHeaders, name) {
+  const values = [];
+  for (let i = 0; i < rawHeaders.length; i += 2) {
+    if (rawHeaders[i] === name) {
+      values.push(rawHeaders[i + 1]);
+    }
+  }
+  return values;
+}
+
+export const testHttpClientResponseSetCookieHeaders = {
+  async test(_ctrl, env) {
+    const { promise, resolve } = Promise.withResolvers();
+
+    // Use Headers so we can avoid differing values due to the http_headers_getsetcookie compat flag
+    const headers = new Headers();
+    headers.append('Set-Cookie', 'a=1');
+    headers.append('Set-Cookie', 'b=2');
+    const expectedSetCookieValues = Array.from(headers)
+      .filter(([name]) => name === 'set-cookie')
+      .map(([, value]) => value);
+
+    http.get(
+      {
+        hostname: env.SIDECAR_HOSTNAME,
+        port: env.HELLO_WORLD_SERVER_PORT,
+        path: '/set-cookie-duplicates',
+      },
+      (res) => {
+        strictEqual(res.statusCode, 200);
+        deepStrictEqual(
+          getRawHeaderValues(res.rawHeaders, 'set-cookie'),
+          expectedSetCookieValues
+        );
+        deepStrictEqual(res.headers['set-cookie'], expectedSetCookieValues);
+        deepStrictEqual(
+          res.headersDistinct['set-cookie'],
+          expectedSetCookieValues
+        );
+        resolve();
+      }
+    );
+
+    await promise;
+  },
+};
+
 export const testGetExport = {
   async test() {
     const { get: getFn } = await import('node:http');