Ensure /404 is not exported during build un-necessarily (#22825)

This ensures we don't export `/404` during the automatic static optimization during build when the `/404` isn't static and won't be used/copied to the final output. x-ref: #22815
vercel · Mar 8, 2021 · cdf8f9a · cdf8f9a
1 parent 3f9c469
commit cdf8f9a
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Showing 2 changed files with 11 additions and 4 deletions.
diff --git a/packages/next/export/index.ts b/packages/next/export/index.ts
@@ -388,7 +388,11 @@ export default async function exportApp(
         })
     )
 
-    if (!exportPathMap['/404'] && !exportPathMap['/404.html']) {
+    if (
+      !options.buildExport &&
+      !exportPathMap['/404'] &&
+      !exportPathMap['/404.html']
+    ) {
       exportPathMap['/404'] = exportPathMap['/404.html'] = {
         page: '/_error',
       }

diff --git a/test/integration/static-404/test/index.test.js b/test/integration/static-404/test/index.test.js
@@ -59,15 +59,18 @@ describe('Static 404 page', () => {
         `
         import Error from 'next/error'
         export default class MyError extends Error {
-          static getInitialProps() {
+          static getInitialProps({ statusCode, req }) {
+            if (req.url === '/404' || req.url === '/404.html') {
+              throw new Error('exported 404 unexpectedly!!!')
+            }
             return {
-              statusCode: 404
+              statusCode,
             }
           }
         }
       `
       )
-      await nextBuild(appDir)
+      await nextBuild(appDir, undefined, { stderr: true, stdout: true })
       await fs.remove(errorPage)
     })