only log export-no-custom-routes warning if unsupported

packages/next/src/server/config.ts

@@ -23,6 +23,7 @@ import { pathHasPrefix } from '../shared/lib/router/utils/path-has-prefix'
 
 import { ZodParsedType, util as ZodUtil } from 'next/dist/compiled/zod'
 import type { ZodError, ZodIssue } from 'next/dist/compiled/zod'
+import { hasNextSupport } from '../telemetry/ci-info'
 
 export { normalizeConfig } from './config-shared'
 export type { DomainLocale, NextConfig } from './config-shared'
@@ -257,20 +258,23 @@ function assignDefaults(
         'Specified "i18n" cannot be used with "output: export". See more info here: https://nextjs.org/docs/messages/export-no-i18n'
       )
     }
-    if (result.rewrites) {
-      throw new Error(
-        'Specified "rewrites" cannot be used with "output: export". See more info here: https://nextjs.org/docs/messages/export-no-custom-routes'
-      )
-    }
-    if (result.redirects) {
-      throw new Error(
-        'Specified "redirects" cannot be used with "output: export". See more info here: https://nextjs.org/docs/messages/export-no-custom-routes'
-      )
-    }
-    if (result.headers) {
-      throw new Error(
-        'Specified "headers" cannot be used with "output: export". See more info here: https://nextjs.org/docs/messages/export-no-custom-routes'
-      )
+
+    if (!hasNextSupport) {
+      if (result.rewrites) {
+        Log.warn(
+          'Specified "rewrites" will not automatically work with "output: export". See more info here: https://nextjs.org/docs/messages/export-no-custom-routes'
+        )
+      }
+      if (result.redirects) {
+        Log.warn(
+          'Specified "redirects" will not automatically work with "output: export". See more info here: https://nextjs.org/docs/messages/export-no-custom-routes'
+        )
+      }
+      if (result.headers) {
+        Log.warn(
+          'Specified "headers" will not automatically work with "output: export". See more info here: https://nextjs.org/docs/messages/export-no-custom-routes'
+        )
+      }
     }
   }
 

test/integration/config-output-export/test/index.test.ts

@@ -64,39 +64,86 @@ describe('config-output-export', () => {
     )
   })
 
-  it('should error with "rewrites" config', async () => {
-    const { stderr } = await runDev({
-      output: 'export',
-      rewrites: [{ source: '/from', destination: '/to' }],
+  describe('when hasNextSupport = false', () => {
+    it('should error with "rewrites" config', async () => {
+      const { stderr } = await runDev({
+        output: 'export',
+        rewrites: [{ source: '/from', destination: '/to' }],
+      })
+      expect(stderr).toContain(
+        'Specified "rewrites" will not automatically work with "output: export".'
+      )
     })
-    expect(stderr).toContain(
-      'Specified "rewrites" cannot be used with "output: export".'
-    )
-  })
 
-  it('should error with "redirects" config', async () => {
-    const { stderr } = await runDev({
-      output: 'export',
-      redirects: [{ source: '/from', destination: '/to', permanent: true }],
+    it('should error with "redirects" config', async () => {
+      const { stderr } = await runDev({
+        output: 'export',
+        redirects: [{ source: '/from', destination: '/to', permanent: true }],
+      })
+      expect(stderr).toContain(
+        'Specified "redirects" will not automatically work with "output: export".'
+      )
+    })
+
+    it('should error with "headers" config', async () => {
+      const { stderr } = await runDev({
+        output: 'export',
+        headers: [
+          {
+            source: '/foo',
+            headers: [{ key: 'x-foo', value: 'val' }],
+          },
+        ],
+      })
+      expect(stderr).toContain(
+        'Specified "headers" will not automatically work with "output: export".'
+      )
     })
-    expect(stderr).toContain(
-      'Specified "redirects" cannot be used with "output: export".'
-    )
   })
 
-  it('should error with "headers" config', async () => {
-    const { stderr } = await runDev({
-      output: 'export',
-      headers: [
-        {
-          source: '/foo',
-          headers: [{ key: 'x-foo', value: 'val' }],
-        },
-      ],
+  describe('when hasNextSupport = true', () => {
+    beforeAll(() => {
+      process.env.NOW_BUILDER = '1'
+    })
+
+    afterAll(() => {
+      delete process.env.NOW_BUILDER
+    })
+
+    it('should error with "rewrites" config', async () => {
+      const { stderr } = await runDev({
+        output: 'export',
+        rewrites: [{ source: '/from', destination: '/to' }],
+      })
+      expect(stderr).not.toContain(
+        'Specified "rewrites" will not automatically work with "output: export".'
+      )
+    })
+
+    it('should error with "redirects" config', async () => {
+      const { stderr } = await runDev({
+        output: 'export',
+        redirects: [{ source: '/from', destination: '/to', permanent: true }],
+      })
+      expect(stderr).not.toContain(
+        'Specified "redirects" will not automatically work with "output: export".'
+      )
+    })
+
+    it('should error with "headers" config', async () => {
+      const { stderr } = await runDev({
+        output: 'export',
+        headers: [
+          {
+            source: '/foo',
+            headers: [{ key: 'x-foo', value: 'val' }],
+          },
+        ],
+      })
+      expect(stderr).not.toContain(
+        'Specified "headers" will not automatically work with "output: export".'
+      )
     })
-    expect(stderr).toContain(
-      'Specified "headers" cannot be used with "output: export".'
-    )
   })
 
   it('should error with api routes function', async () => {