fix local development proxy to docs.github.com for Copilot Search (#56311)

Author: Ebonsignori

src/frame/middleware/api.ts

@@ -4,6 +4,7 @@ import { createProxyMiddleware } from 'http-proxy-middleware'
 import events from '@/events/middleware.js'
 import anchorRedirect from '@/rest/api/anchor-redirect.js'
 import aiSearch from '@/search/middleware/ai-search'
+import aiSearchLocalProxy from '@/search/middleware/ai-search-local-proxy'
 import search from '@/search/middleware/search-routes.js'
 import pageList from '@/article-api/middleware/pagelist'
 import article from '@/article-api/middleware/article'
@@ -31,16 +32,7 @@ if (process.env.CSE_COPILOT_ENDPOINT || process.env.NODE_ENV === 'test') {
   console.log(
     'Proxying AI Search requests to docs.github.com. To use the cse-copilot endpoint, set the CSE_COPILOT_ENDPOINT environment variable.',
   )
-  router.use(
-    '/ai-search',
-    createProxyMiddleware({
-      target: 'https://docs.github.com',
-      changeOrigin: true,
-      pathRewrite: function (path, req: ExtendedRequest) {
-        return req.originalUrl
-      },
-    }),
-  )
+  router.use(aiSearchLocalProxy)
 }
 if (process.env.ELASTICSEARCH_URL) {
   router.use('/search', search)

src/search/middleware/ai-search-local-proxy.ts

@@ -0,0 +1,70 @@
+// When in local development we want to proxy to the ai-search route at docs.github.com
+
+import { Router, Request, Response, NextFunction } from 'express'
+import got from 'got'
+import { pipeline } from 'node:stream'
+
+const router = Router()
+
+const hopByHop = new Set([
+  'connection',
+  'keep-alive',
+  'proxy-authenticate',
+  'proxy-authorization',
+  'te',
+  'trailers',
+  'transfer-encoding',
+  'upgrade',
+])
+
+function filterRequestHeaders(src: Request['headers']) {
+  const out: Record<string, string | string[]> = {}
+  for (const [key, value] of Object.entries(src)) {
+    if (!value) continue
+    const k = key.toLowerCase()
+    if (hopByHop.has(k) || k === 'cookie' || k === 'host') continue
+    out[key] = value
+  }
+  out['accept'] = 'application/x-ndjson'
+  out['content-type'] = 'application/json'
+  return out
+}
+
+router.post('/ai-search/v1', async (req: Request, res: Response, next: NextFunction) => {
+  try {
+    const upstream = got.stream.post('https://docs.github.com/api/ai-search/v1', {
+      headers: filterRequestHeaders(req.headers),
+      body: JSON.stringify(req.body ?? {}),
+      decompress: false,
+      throwHttpErrors: false,
+      retry: { limit: 0 },
+    })
+
+    upstream.on('response', (uRes) => {
+      res.status(uRes.statusCode || 500)
+
+      for (const [k, v] of Object.entries(uRes.headers)) {
+        if (!v) continue
+        const key = k.toLowerCase()
+        // Never forward hop-by-hop; got already handles chunked → strip content-length
+        if (hopByHop.has(key) || key === 'content-length') continue
+        res.setHeader(k, v as string)
+      }
+      res.flushHeaders?.()
+    })
+
+    pipeline(upstream, res, (err) => {
+      if (err) {
+        console.error('[ai-search proxy] pipeline error:', err)
+        if (!res.headersSent) res.status(502).end('Bad Gateway')
+      }
+    })
+
+    upstream.on('error', (err) => console.error('[ai-search proxy] upstream error:', err))
+  } catch (err) {
+    console.error('[ai-search proxy] request failed:', err)
+    next(err)
+  }
+})
+
+export default router