refactor(rsc-mf): share safe proxy response helper

Author: cursoragent

tests/integration/rsc-mf/host/server/modern.server.ts

@@ -10,6 +10,7 @@ import {
   isExposeAssetRequestPath,
   resolveManifestFallbackAssetPath,
 } from '../../shared/manifestFallback';
+import { createSafeProxyResponse } from '../../shared/proxyResponse';
 
 const REMOTE_MANIFEST_PATH = '/static/mf-manifest.json';
 
@@ -99,17 +100,6 @@ const shouldProxyRemoteAsset = (pathname: string) => {
   return false;
 };
 
-const createProxyResponse = (upstream: Response) => {
-  const headers = new Headers(upstream.headers);
-  headers.delete('content-length');
-  headers.delete('content-encoding');
-  headers.delete('transfer-encoding');
-  return new Response(upstream.body, {
-    status: upstream.status,
-    headers,
-  });
-};
-
 const proxyRemoteFederationAsset: MiddlewareHandler = async (c, next) => {
   const requestHeaders = c.req.headers;
   const isInternalFallbackFetch =
@@ -151,7 +141,7 @@ const proxyRemoteFederationAsset: MiddlewareHandler = async (c, next) => {
     return;
   }
 
-  c.res = createProxyResponse(resolvedUpstream);
+  c.res = createSafeProxyResponse(resolvedUpstream);
 };
 
 export default defineServerConfig({

tests/integration/rsc-mf/remote/server/modern.server.ts

@@ -10,20 +10,10 @@ import {
   isExposeAssetRequestPath,
   resolveManifestFallbackAssetPath,
 } from '../../shared/manifestFallback';
+import { createSafeProxyResponse } from '../../shared/proxyResponse';
 
 const REMOTE_MANIFEST_PATH = '/static/mf-manifest.json';
 
-const createProxyResponse = (upstream: Response) => {
-  const headers = new Headers(upstream.headers);
-  headers.delete('content-length');
-  headers.delete('content-encoding');
-  headers.delete('transfer-encoding');
-  return new Response(upstream.body, {
-    status: upstream.status,
-    headers,
-  });
-};
-
 const recoverRemoteExposeAssetMiddleware: MiddlewareHandler = async (
   c,
   next,
@@ -96,7 +86,7 @@ const recoverRemoteExposeAssetMiddleware: MiddlewareHandler = async (
     return;
   }
 
-  c.res = createProxyResponse(fallbackAssetResponse);
+  c.res = createSafeProxyResponse(fallbackAssetResponse);
 };
 
 export default defineServerConfig({

tests/integration/rsc-mf/shared/proxyResponse.ts

@@ -0,0 +1,16 @@
+const HOP_BY_HOP_RESPONSE_HEADERS = [
+  'content-length',
+  'content-encoding',
+  'transfer-encoding',
+];
+
+export const createSafeProxyResponse = (upstream: Response) => {
+  const headers = new Headers(upstream.headers);
+  for (const headerName of HOP_BY_HOP_RESPONSE_HEADERS) {
+    headers.delete(headerName);
+  }
+  return new Response(upstream.body, {
+    status: upstream.status,
+    headers,
+  });
+};

tests/integration/rsc-mf/tests/proxyResponse.test.ts

@@ -0,0 +1,41 @@
+import { createSafeProxyResponse } from '../shared/proxyResponse';
+
+describe('rsc-mf proxy response helper', () => {
+  it('removes hop-by-hop response headers while preserving payload', async () => {
+    const upstream = new Response('proxied-body', {
+      status: 202,
+      headers: {
+        'content-type': 'application/javascript',
+        'content-length': '999',
+        'content-encoding': 'gzip',
+        'transfer-encoding': 'chunked',
+      },
+    });
+
+    const proxied = createSafeProxyResponse(upstream);
+
+    expect(proxied.status).toBe(202);
+    expect(proxied.headers.get('content-type')).toBe('application/javascript');
+    expect(proxied.headers.get('content-length')).toBeNull();
+    expect(proxied.headers.get('content-encoding')).toBeNull();
+    expect(proxied.headers.get('transfer-encoding')).toBeNull();
+    await expect(proxied.text()).resolves.toBe('proxied-body');
+  });
+
+  it('keeps unrelated response headers intact', () => {
+    const upstream = new Response('ok', {
+      status: 200,
+      headers: {
+        'cache-control': 'public,max-age=31536000',
+        etag: '"abc123"',
+      },
+    });
+
+    const proxied = createSafeProxyResponse(upstream);
+
+    expect(proxied.headers.get('cache-control')).toBe(
+      'public,max-age=31536000',
+    );
+    expect(proxied.headers.get('etag')).toBe('"abc123"');
+  });
+});