fix: external redirects not being matched correctly closes #3770 (#4109)

* test: add failing test to reproduce issue with 301 redirects

* fix: external redirects not being matched correctly

Co-authored-by: Erez Rokah <erezrokah@users.noreply.github.com>
Co-authored-by: kodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>

Author: 3 people

Diff for: src/utils/proxy.js

@@ -213,6 +213,10 @@ const serveRedirect = async function ({ match, options, proxy, req, res }) {
 
     const destURL = stripOrigin(dest)
 
+    if (isExternal(match)) {
+      return proxyToExternalUrl({ req, res, dest, destURL })
+    }
+
     if (isRedirect(match)) {
       res.writeHead(match.status, {
         Location: destURL,
@@ -222,10 +226,6 @@ const serveRedirect = async function ({ match, options, proxy, req, res }) {
       return
     }
 
-    if (isExternal(match)) {
-      return proxyToExternalUrl({ req, res, dest, destURL })
-    }
-
     const ct = req.headers['content-type'] ? contentType.parse(req).type : ''
     if (
       req.method === 'POST' &&

Diff for: tests/integration/0.command.dev.test.js

@@ -199,6 +199,25 @@ testMatrix.forEach(({ args }) => {
     })
   })
 
+  test(testName('should follow 301 redirect to an external server', args), async (t) => {
+    await withSiteBuilder('site-redirects-file-to-external-301', async (builder) => {
+      const externalServer = startExternalServer()
+      const { port } = externalServer.address()
+      builder.withRedirectsFile({
+        redirects: [{ from: '/api/*', to: `http://localhost:${port}/:splat`, status: 301 }],
+      })
+
+      await builder.buildAsync()
+
+      await withDevServer({ cwd: builder.directory, args }, async (server) => {
+        const response = await got(`${server.url}/api/ping`).json()
+        t.deepEqual(response, { body: {}, method: 'GET', url: '/ping' })
+      })
+
+      externalServer.close()
+    })
+  })
+
   test(testName('should redirect POST request if content-type is missing', args), async (t) => {
     await withSiteBuilder('site-with-post-no-content-type', async (builder) => {
       builder.withNetlifyToml({