fix(fetch): cookie with domain=localhost (#18998)

Fixes https://github.com/microsoft/playwright/issues/18362

packages/playwright-core/src/server/fetch.ts

@@ -207,7 +207,7 @@ export abstract class APIRequestContext extends SdkObject {
       if (!cookie.domain)
         cookie.domain = url.hostname;
       else
-        assert(cookie.domain.startsWith('.'));
+        assert(cookie.domain.startsWith('.') || !cookie.domain.includes('.'));
       if (!domainMatches(url.hostname, cookie.domain!))
         continue;
       // https://datatracker.ietf.org/doc/html/rfc6265#section-5.2.4
@@ -587,7 +587,7 @@ function parseCookie(header: string): channels.NetworkCookie | null {
         break;
       case 'domain':
         cookie.domain = value.toLocaleLowerCase() || '';
-        if (cookie.domain && !cookie.domain.startsWith('.'))
+        if (cookie.domain && !cookie.domain.startsWith('.') && cookie.domain.includes('.'))
           cookie.domain = '.' + cookie.domain;
         break;
       case 'path':

tests/library/browsercontext-fetch.spec.ts

@@ -1072,6 +1072,19 @@ it('should support SameSite cookie attribute over https', async ({ contextFactor
   }
 });
 
+it('should set domain=localhost cookie', async ({ context, server, browserName, isWindows }) => {
+  server.setRoute('/empty.html', (req, res) => {
+    res.setHeader('Set-Cookie', `name=val; Domain=localhost; Path=/;`);
+    res.end();
+  });
+  await context.request.get(server.EMPTY_PAGE);
+  const [cookie] = await context.cookies();
+  expect(cookie).toBeTruthy();
+  expect(cookie.name).toBe('name');
+  expect(cookie.value).toBe('val');
+});
+
+
 it('should support set-cookie with SameSite and without Secure attribute over HTTP', async ({ page, server, browserName, isWindows }) => {
   for (const value of ['None', 'Lax', 'Strict']) {
     await it.step(`SameSite=${value}`, async () => {

tests/library/browsercontext-proxy.spec.ts

@@ -91,6 +91,26 @@ it('should use proxy', async ({ contextFactory, server, proxyServer }) => {
   await context.close();
 });
 
+
+it('should set cookie for top-level domain', async ({ contextFactory, server, proxyServer, browserName, isLinux }) => {
+  it.fixme(browserName === 'webkit' && isLinux);
+  proxyServer.forwardTo(server.PORT);
+  const context = await contextFactory({
+    proxy: { server: `localhost:${proxyServer.PORT}` }
+  });
+  server.setRoute('/empty.html', (req, res) => {
+    res.setHeader('Set-Cookie', `name=val; Domain=codes; Path=/;`);
+    res.end();
+  });
+
+  await context.request.get('http://codes/empty.html');
+  const [cookie] = await context.cookies();
+  expect(cookie).toBeTruthy();
+  expect(cookie.name).toBe('name');
+  expect(cookie.value).toBe('val');
+  await context.close();
+});
+
 it.describe('should proxy local network requests', () => {
   for (const additionalBypass of [false, true]) {
     it.describe(additionalBypass ? 'with other bypasses' : 'by default', () => {