Test fixes for Babel mode

packages/next/build/babel/loader/get-config.ts

@@ -1,7 +1,8 @@
+import { readFileSync } from 'fs'
+
 import { createConfigItem, loadOptions } from 'next/dist/compiled/babel/core'
 import loadConfig from 'next/dist/compiled/babel/core-lib-config'
 
-import nextBabelPreset from '../preset'
 import { NextBabelLoaderOptions, NextJsLoaderContext } from './types'
 import { consumeIterator } from './util'
 
@@ -31,8 +32,10 @@ interface CharacteristicsGermaneToCaching {
   isPageFile: boolean
   isNextDist: boolean
   hasModuleExports: boolean
+  fileExt: string
 }
 
+const fileExtensionRegex = /\.([a-z]+)$/
 function getCacheCharacteristics(
   loaderOptions: NextBabelLoaderOptions,
   source: string,
@@ -42,12 +45,14 @@ function getCacheCharacteristics(
   const isPageFile = filename.startsWith(pagesDir)
   const isNextDist = nextDistPath.test(filename)
   const hasModuleExports = source.indexOf('module.exports') !== -1
+  const fileExt = fileExtensionRegex.exec(filename)?.[1] || 'unknown'
 
   return {
     isServer,
     isPageFile,
     isNextDist,
     hasModuleExports,
+    fileExt,
   }
 }
 
@@ -134,6 +139,46 @@ function getPlugins(
   ].filter(Boolean)
 }
 
+const isJsonFile = /\.(json|babelrc)$/
+const isJsFile = /\.js$/
+
+/**
+ * While this function does block execution while reading from disk, it
+ * should not introduce any issues.  The function is only invoked when
+ * generating a fresh config, and only a small handful of configs should
+ * be generated during compilation.
+ */
+function getCustomBabelConfig(configFilePath: string) {
+  if (isJsonFile.exec(configFilePath)) {
+    const babelConfigRaw = readFileSync(configFilePath, 'utf8')
+    return JSON.parse(babelConfigRaw)
+  } else if (isJsFile.exec(configFilePath)) {
+    return require(configFilePath)
+  }
+  throw new Error(
+    'The Next Babel loader does not support MJS or CJS config files.'
+  )
+}
+
+function getCustomPresets(presets: any[], customConfig: any) {
+  presets = [...presets, ...customConfig?.presets]
+
+  const hasNextBabelPreset = (customConfig?.presets || [])
+    .filter((preset: any) => {
+      return (
+        preset === 'next/babel' ||
+        (Array.isArray(preset) && preset[0] === 'next/babel')
+      )
+    })
+    .reduce((memo: boolean, presetFound: boolean) => memo || presetFound, false)
+
+  if (!hasNextBabelPreset) {
+    presets.push('next/babel')
+  }
+
+  return presets
+}
+
 /**
  * Generate a new, flat Babel config, ready to be handed to Babel-traverse.
  * This config should have no unresolved overrides, presets, etc.
@@ -146,19 +191,28 @@ function getFreshConfig(
   filename: string,
   inputSourceMap?: object | null
 ) {
-  const {
+  let {
     presets = [],
     isServer,
     pagesDir,
     development,
-    hasReactRefresh,
     hasJsxRuntime,
-    babelrc,
+    configFile,
   } = loaderOptions
-  const nextPresetItem = createConfigItem(nextBabelPreset, { type: 'preset' })
+
+  let customPlugins = []
+  if (configFile) {
+    const customConfig = getCustomBabelConfig(configFile)
+    presets = getCustomPresets(presets, customConfig)
+    if (customConfig.plugins) {
+      customPlugins = customConfig.plugins
+    }
+  } else {
+    presets = [...presets, 'next/babel']
+  }
 
   let options = {
-    babelrc,
+    babelrc: false,
     cloneInputAst: false,
     filename,
     inputSourceMap: inputSourceMap || undefined,
@@ -167,17 +221,20 @@ function getFreshConfig(
     // but allow users to override if they want.
     sourceMaps:
       loaderOptions.sourceMaps === undefined
-        ? inputSourceMap
+        ? this.sourceMap
         : loaderOptions.sourceMaps,
 
     // Ensure that Webpack will get a full absolute path in the sourcemap
     // so that it can properly map the module back to its internal cached
     // modules.
     sourceFileName: filename,
 
-    plugins: getPlugins(loaderOptions, cacheCharacteristics),
+    plugins: [
+      ...getPlugins(loaderOptions, cacheCharacteristics),
+      ...customPlugins,
+    ],
 
-    presets: [...presets, nextPresetItem],
+    presets,
 
     overrides: loaderOptions.overrides,
 
@@ -197,8 +254,7 @@ function getFreshConfig(
 
       isServer,
       pagesDir,
-      development,
-      hasReactRefresh,
+      isDev: development,
       hasJsxRuntime,
 
       ...loaderOptions.caller,
@@ -233,19 +289,21 @@ function getCacheKey(cacheCharacteristics: CharacteristicsGermaneToCaching) {
     isPageFile,
     isNextDist,
     hasModuleExports,
+    fileExt,
   } = cacheCharacteristics
 
-  return (
+  const flags =
     0 |
     (isServer ? 0b0001 : 0) |
     (isPageFile ? 0b0010 : 0) |
     (isNextDist ? 0b0100 : 0) |
     (hasModuleExports ? 0b1000 : 0)
-  )
+
+  return fileExt + flags
 }
 
 type BabelConfig = any
-const configCache: Map<number, BabelConfig> = new Map()
+const configCache: Map<any, BabelConfig> = new Map()
 
 export default function getConfig(
   this: NextJsLoaderContext,
@@ -271,10 +329,17 @@ export default function getConfig(
 
   const cacheKey = getCacheKey(cacheCharacteristics)
   if (configCache.has(cacheKey)) {
+    const cachedConfig = configCache.get(cacheKey)
+
     return {
-      ...configCache.get(cacheKey),
-      filename,
-      sourceFileName: filename,
+      ...cachedConfig,
+      options: {
+        ...cachedConfig.options,
+        cwd: loaderOptions.cwd,
+        root: loaderOptions.cwd,
+        filename,
+        sourceFileName: filename,
+      },
     }
   }
 

packages/next/build/babel/loader/index.ts

@@ -1,4 +1,3 @@
-import { inspect } from 'util'
 import { getOptions } from 'next/dist/compiled/loader-utils'
 import { trace } from '../../../telemetry/trace'
 import { Span } from '../../../telemetry/trace'
@@ -52,9 +51,6 @@ const nextBabelLoaderOuter = function nextBabelLoaderOuter(
       ([transformedSource, outputSourceMap]) =>
         callback?.(null, transformedSource, outputSourceMap || inputSourceMap),
       (err) => {
-        console.error(
-          `Problem encountered in next-babel-turbo-loader. \n${inspect(err)}`
-        )
         callback?.(err)
       }
     )

packages/next/build/babel/loader/types.d.ts

@@ -15,5 +15,6 @@ export interface NextBabelLoaderOptions {
   sourceMaps?: any[]
   overrides: any
   caller: any
-  babelrc: boolean
+  configFile: string | undefined
+  cwd: string
 }

packages/next/build/webpack-config.ts

@@ -209,7 +209,7 @@ export default async function getBaseWebpackConfig(
     // fixed in rc.1.
     semver.gte(reactVersion!, '17.0.0-rc.1')
 
-  const babelrc = await [
+  const babelConfigFile = await [
     '.babelrc',
     '.babelrc.json',
     '.babelrc.js',
@@ -219,9 +219,13 @@ export default async function getBaseWebpackConfig(
     'babel.config.json',
     'babel.config.mjs',
     'babel.config.cjs',
-  ].reduce(async (memo: boolean | Promise<boolean>, filename) => {
-    return (await memo) || (await fileExists(path.join(dir, filename)))
-  }, false)
+  ].reduce(async (memo: Promise<string | undefined>, filename) => {
+    const configFilePath = path.join(dir, filename)
+    return (
+      (await memo) ||
+      ((await fileExists(configFilePath)) ? configFilePath : undefined)
+    )
+  }, Promise.resolve(undefined))
 
   const distDir = path.join(dir, config.distDir)
 
@@ -232,7 +236,7 @@ export default async function getBaseWebpackConfig(
     babel: {
       loader: babelLoader,
       options: {
-        babelrc,
+        configFile: babelConfigFile,
         isServer,
         distDir,
         pagesDir,

test/integration/config-devtool-dev/test/index.test.js

@@ -15,7 +15,7 @@ jest.setTimeout(1000 * 30)
 
 const appDir = join(__dirname, '../')
 
-describe('devtool set in developmemt mode in next config', () => {
+describe('devtool set in development mode in next config', () => {
   it('should warn and revert when a devtool is set in development mode', async () => {
     let stderr = ''