Fix long URLs causing 400s with dynamic routes/rewrites (vercel#26221)

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

packages/next/lib/file-exists.ts

@@ -16,7 +16,7 @@ export async function fileExists(
     }
     return true
   } catch (err) {
-    if (err.code === 'ENOENT') {
+    if (err.code === 'ENOENT' || err.code === 'ENAMETOOLONG') {
       return false
     }
     throw err

test/integration/custom-routes/test/index.test.js

@@ -39,6 +39,17 @@ let appPort
 let app
 
 const runTests = (isDev = false) => {
+  it('should support long URLs for rewrites', async () => {
+    const res = await fetchViaHTTP(
+      appPort,
+      '/catchall-rewrite/a9btBxtHQALZ6cxfuj18X6OLGNSkJVzrOXz41HG4QwciZfn7ggRZzPx21dWqGiTBAqFRiWvVNm5ko2lpyso5jtVaXg88dC1jKfqI2qmIcdeyJat8xamrIh2LWnrYRrsBcoKfQU65KHod8DPANuzPS3fkVYWlmov05GQbc82HwR1exOvPVKUKb5gBRWiN0WOh7hN4QyezIuq3dJINAptFQ6m2bNGjYACBRk4MOSHdcQG58oq5Ch7luuqrl9EcbWSa'
+    )
+
+    const html = await res.text()
+    expect(res.status).toBe(200)
+    expect(html).toContain('/with-params')
+  })
+
   it('should resolveHref correctly navigating through history', async () => {
     const browser = await webdriver(appPort, '/')
     await browser.eval('window.beforeNav = 1')

test/integration/dynamic-routing/pages/dash/[hello-world].js

@@ -1 +1,3 @@
-export default () => 'hi'
+export default function Page(props) {
+  return 'hi'
+}

test/integration/dynamic-routing/test/index.test.js

@@ -30,6 +30,18 @@ const appDir = join(__dirname, '../')
 const buildIdPath = join(appDir, '.next/BUILD_ID')
 
 function runTests(dev) {
+  it('should support long URLs for dynamic routes', async () => {
+    const res = await fetchViaHTTP(
+      appPort,
+      '/dash/a9btBxtHQALZ6cxfuj18X6OLGNSkJVzrOXz41HG4QwciZfn7ggRZzPx21dWqGiTBAqFRiWvVNm5ko2lpyso5jtVaXg88dC1jKfqI2qmIcdeyJat8xamrIh2LWnrYRrsBcoKfQU65KHod8DPANuzPS3fkVYWlmov05GQbc82HwR1exOvPVKUKb5gBRWiN0WOh7hN4QyezIuq3dJINAptFQ6m2bNGjYACBRk4MOSHdcQG58oq5Ch7luuqrl9EcbWSa'
+    )
+
+    const html = await res.text()
+    expect(res.status).toBe(200)
+    expect(html).toContain('hi')
+    expect(html).toContain('/dash/[hello-world]')
+  })
+
   it('should handle only query on dynamic route', async () => {
     const browser = await webdriver(appPort, '/post-1')
 

test/integration/production/pages/invalid-param/[slug].js

@@ -1,7 +1,7 @@
 import { useRouter } from 'next/router'
 
 export default function Page() {
-  return <p>hello {useRouter().query}</p>
+  return <p>hello {useRouter().query.slug}</p>
 }
 
 export const getServerSideProps = () => {