Font loader with babel error

packages/next/build/webpack-config.ts

@@ -634,6 +634,11 @@ export default async function getBaseWebpackConfig(
     loggedIgnoredCompilerOptions = true
   }
 
+  if (!useSWCLoader && config.experimental.fontLoaders) {
+    Log.error('`experimental.fontLoaders` requires SWC but found Babel config.')
+    process.exit(1)
+  }
+
   const getBabelLoader = () => {
     return {
       loader: require.resolve('./babel/loader/index'),

test/e2e/next-font/babel.test.ts

@@ -0,0 +1,33 @@
+import { createNext, FileRef } from 'e2e-utils'
+import { NextInstance } from 'test/lib/next-modes/base'
+import { join } from 'path'
+
+describe('@next/font/google babel', () => {
+  const isNextStart = (global as any).isNextStart
+  let next: NextInstance
+
+  if (!isNextStart) {
+    it('should only run on next start', () => {})
+    return
+  }
+
+  beforeAll(async () => {
+    next = await createNext({
+      skipStart: true,
+      files: new FileRef(join(__dirname, 'babel')),
+      dependencies: {
+        '@next/font': 'canary',
+      },
+    })
+  })
+  afterAll(() => next.destroy())
+
+  test('Build error when using babel', async () => {
+    await expect(next.start()).rejects.toThrow(
+      'next build failed with code/signal 1'
+    )
+    expect(next.cliOutput).toMatch(
+      /`experimental.fontLoaders` requires SWC but found Babel config./
+    )
+  })
+})

test/e2e/next-font/babel/.babelrc

@@ -0,0 +1,4 @@
+{
+  "presets": ["next/babel"],
+  "plugins": []
+}

test/e2e/next-font/babel/pages/index.js

@@ -0,0 +1,3 @@
+export default function Page() {
+  return <p>Hello world</p>
+}

test/development/next-font/font-loader-in-document-error.test.ts → test/e2e/next-font/font-loader-in-document-error.test.ts

@@ -5,8 +5,14 @@ import webdriver from 'next-webdriver'
 import { join } from 'path'
 
 describe('font-loader-in-document-error', () => {
+  const isDev = (global as any).isNextDev
   let next: NextInstance
 
+  if (!isDev) {
+    it('should only run on next dev', () => {})
+    return
+  }
+
   beforeAll(async () => {
     next = await createNext({
       files: {

test/e2e/next-font/font-loader-in-document/next.config.js

@@ -0,0 +1,9 @@
+module.exports = {
+  experimental: {
+    fontLoaders: {
+      '@next/font/google': {
+        subsets: ['latin'],
+      },
+    },
+  },
+}