feat: respond multiple headers with same key

docs/api.md

@@ -5122,7 +5122,7 @@ ResourceType will be one of the following: `document`, `stylesheet`, `image`, `m
 
 - `response` <[Object]> Response that will fulfill this request
   - `status` <[number]> Response status code, defaults to `200`.
-  - `headers` <[Object]> Optional response headers. Header values will be converted to a string.
+  - `headers` <[Object]> Optional response headers. Header values should be a string or a string array.
   - `contentType` <[string]> If set, equals to setting `Content-Type` response header
   - `body` <[string]|[Buffer]> Optional response body
 - `priority` <[number]> - Optional intercept abort priority. If provided, intercept will be resolved using coopeative handling rules. Otherwise, intercept will be resolved immediately.

src/common/HTTPRequest.ts

@@ -555,12 +555,15 @@ export class HTTPRequest {
         ? Buffer.from(response.body)
         : (response.body as Buffer) || null;
 
-    const responseHeaders: Record<string, string> = {};
+    const responseHeaders: Record<string, string | string[]> = {};
     if (response.headers) {
-      for (const header of Object.keys(response.headers))
-        responseHeaders[header.toLowerCase()] = String(
-          response.headers[header]
-        );
+      for (const header of Object.keys(response.headers)) {
+        const value = response.headers[header];
+
+        responseHeaders[header.toLowerCase()] = Array.isArray(value)
+          ? value.map((item) => String(item))
+          : String(value);
+      }
     }
     if (response.contentType)
       responseHeaders['content-type'] = response.contentType;
@@ -696,12 +699,17 @@ const errorReasons: Record<ErrorCode, Protocol.Network.ErrorReason> = {
 export type ActionResult = 'continue' | 'abort' | 'respond';
 
 function headersArray(
-  headers: Record<string, string>
+  headers: Record<string, string | string[]>
 ): Array<{ name: string; value: string }> {
   const result = [];
   for (const name in headers) {
-    if (!Object.is(headers[name], undefined))
-      result.push({ name, value: headers[name] + '' });
+    const value = headers[name];
+
+    if (!Object.is(value, undefined)) {
+      const values = Array.isArray(value) ? value : [value];
+
+      result.push(...values.map((value) => ({ name, value: value + '' })));
+    }
   }
   return result;
 }

test/requestinterception.spec.ts

@@ -710,6 +710,33 @@ describe('request interception', function () {
       );
       expect(response.url()).toBe(server.EMPTY_PAGE);
     });
+    it('should allow mocking multiple headers with same key', async () => {
+      const { page, server } = getTestState();
+
+      await page.setRequestInterception(true);
+      page.on('request', (request) => {
+        request.respond({
+          status: 200,
+          headers: {
+            foo: 'bar',
+            arr: ['1', '2'],
+            'set-cookie': ['first=1', 'second=2'],
+          },
+          body: 'Hello world',
+        });
+      });
+      const response = await page.goto(server.EMPTY_PAGE);
+      const cookies = await page.cookies();
+      const firstCookie = cookies.find((cookie) => cookie.name === 'first');
+      const secondCookie = cookies.find((cookie) => cookie.name === 'second');
+      expect(response.status()).toBe(200);
+      expect(response.headers().foo).toBe('bar');
+      expect(response.headers().arr).toBe('1\n2');
+      // request.respond() will not trigger Network.responseReceivedExtraInfo
+      // fail to get 'set-cookie' header from response
+      expect(firstCookie?.value).toBe('1');
+      expect(secondCookie?.value).toBe('2');
+    });
     it('should allow mocking binary responses', async () => {
       const { page, server } = getTestState();