config.ts

import fs from 'node:fs'
import path from 'node:path'
import { parse as parseUrl, pathToFileURL } from 'node:url'
import { performance } from 'node:perf_hooks'
import { createRequire } from 'node:module'
import colors from 'picocolors'
import type { Alias, AliasOptions } from 'types/alias'
import aliasPlugin from '@rollup/plugin-alias'
import { build } from 'esbuild'
import type { Plugin as ESBuildPlugin } from 'esbuild'
import type { RollupOptions } from 'rollup'
import type { Plugin } from './plugin'
import type {
  BuildAdvancedBaseConfig,
  BuildOptions,
  ResolvedBuildAdvancedBaseConfig,
  ResolvedBuildOptions
} from './build'
import { resolveBuildAdvancedBaseConfig, resolveBuildOptions } from './build'
import type { ResolvedServerOptions, ServerOptions } from './server'
import { resolveServerOptions } from './server'
import type { PreviewOptions, ResolvedPreviewOptions } from './preview'
import { resolvePreviewOptions } from './preview'
import type { CSSOptions } from './plugins/css'
import {
  asyncFlatten,
  createDebugger,
  createFilter,
  dynamicImport,
  isExternalUrl,
  isObject,
  isTS,
  lookupFile,
  mergeAlias,
  mergeConfig,
  normalizeAlias,
  normalizePath
} from './utils'
import { resolvePlugins } from './plugins'
import type { ESBuildOptions } from './plugins/esbuild'
import {
  CLIENT_ENTRY,
  DEFAULT_ASSETS_RE,
  DEFAULT_CONFIG_FILES,
  ENV_ENTRY
} from './constants'
import type { InternalResolveOptions, ResolveOptions } from './plugins/resolve'
import { resolvePlugin } from './plugins/resolve'
import type { LogLevel, Logger } from './logger'
import { createLogger } from './logger'
import type { DepOptimizationOptions } from './optimizer'
import type { JsonOptions } from './plugins/json'
import type { PluginContainer } from './server/pluginContainer'
import { createPluginContainer } from './server/pluginContainer'
import type { PackageCache } from './packages'
import { loadEnv, resolveEnvPrefix } from './env'
import type { ResolvedSSROptions, SSROptions } from './ssr'
import { resolveSSROptions } from './ssr'

const debug = createDebugger('vite:config')

export type { BuildAdvancedBaseOptions, BuildAdvancedBaseConfig } from './build'

// NOTE: every export in this file is re-exported from ./index.ts so it will
// be part of the public API.
export interface ConfigEnv {
  command: 'build' | 'serve'
  mode: string
}

/**
 * spa: include SPA fallback middleware and configure sirv with `single: true` in preview
 *
 * mpa: only include non-SPA HTML middlewares
 *
 * custom: don't include HTML middlewares
 */
export type AppType = 'spa' | 'mpa' | 'custom'

export type UserConfigFn = (env: ConfigEnv) => UserConfig | Promise<UserConfig>
export type UserConfigExport = UserConfig | Promise<UserConfig> | UserConfigFn

/**
 * Type helper to make it easier to use vite.config.ts
 * accepts a direct {@link UserConfig} object, or a function that returns it.
 * The function receives a {@link ConfigEnv} object that exposes two properties:
 * `command` (either `'build'` or `'serve'`), and `mode`.
 */
export function defineConfig(config: UserConfigExport): UserConfigExport {
  return config
}

export type PluginOption =
  | Plugin
  | false
  | null
  | undefined
  | PluginOption[]
  | Promise<Plugin | false | null | undefined | PluginOption[]>

export interface UserConfig {
  /**
   * Project root directory. Can be an absolute path, or a path relative from
   * the location of the config file itself.
   * @default process.cwd()
   */
  root?: string
  /**
   * Base public path when served in development or production.
   * @default '/'
   */
  base?: string
  /**
   * Directory to serve as plain static assets. Files in this directory are
   * served and copied to build dist dir as-is without transform. The value
   * can be either an absolute file system path or a path relative to <root>.
   *
   * Set to `false` or an empty string to disable copied static assets to build dist dir.
   * @default 'public'
   */
  publicDir?: string | false
  /**
   * Directory to save cache files. Files in this directory are pre-bundled
   * deps or some other cache files that generated by vite, which can improve
   * the performance. You can use `--force` flag or manually delete the directory
   * to regenerate the cache files. The value can be either an absolute file
   * system path or a path relative to <root>.
   * Default to `.vite` when no `package.json` is detected.
   * @default 'node_modules/.vite'
   */
  cacheDir?: string
  /**
   * Explicitly set a mode to run in. This will override the default mode for
   * each command, and can be overridden by the command line --mode option.
   */
  mode?: string
  /**
   * Define global variable replacements.
   * Entries will be defined on `window` during dev and replaced during build.
   */
  define?: Record<string, any>
  /**
   * Array of vite plugins to use.
   */
  plugins?: PluginOption[]
  /**
   * Configure resolver
   */
  resolve?: ResolveOptions & { alias?: AliasOptions }
  /**
   * CSS related options (preprocessors and CSS modules)
   */
  css?: CSSOptions
  /**
   * JSON loading options
   */
  json?: JsonOptions
  /**
   * Transform options to pass to esbuild.
   * Or set to `false` to disable esbuild.
   */
  esbuild?: ESBuildOptions | false
  /**
   * Specify additional picomatch patterns to be treated as static assets.
   */
  assetsInclude?: string | RegExp | (string | RegExp)[]
  /**
   * Server specific options, e.g. host, port, https...
   */
  server?: ServerOptions
  /**
   * Build specific options
   */
  build?: BuildOptions
  /**
   * Preview specific options, e.g. host, port, https...
   */
  preview?: PreviewOptions
  /**
   * Dep optimization options
   */
  optimizeDeps?: DepOptimizationOptions
  /**
   * SSR specific options
   */
  ssr?: SSROptions
  /**
   * Experimental features
   *
   * Features under this field could change in the future and might NOT follow semver.
   * Please be careful and always pin Vite's version when using them.
   * @experimental
   */
  experimental?: ExperimentalOptions
  /**
   * Legacy options
   *
   * Features under this field only follow semver for patches, they could be removed in a
   * future minor version. Please always pin Vite's version to a minor when using them.
   */
  legacy?: LegacyOptions
  /**
   * Log level.
   * Default: 'info'
   */
  logLevel?: LogLevel
  /**
   * Custom logger.
   */
  customLogger?: Logger
  /**
   * Default: true
   */
  clearScreen?: boolean
  /**
   * Environment files directory. Can be an absolute path, or a path relative from
   * the location of the config file itself.
   * @default root
   */
  envDir?: string
  /**
   * Env variables starts with `envPrefix` will be exposed to your client source code via import.meta.env.
   * @default 'VITE_'
   */
  envPrefix?: string | string[]
  /**
   * Worker bundle options
   */
  worker?: {
    /**
     * Output format for worker bundle
     * @default 'iife'
     */
    format?: 'es' | 'iife'
    /**
     * Vite plugins that apply to worker bundle
     */
    plugins?: PluginOption[]
    /**
     * Rollup options to build worker bundle
     */
    rollupOptions?: Omit<
      RollupOptions,
      'plugins' | 'input' | 'onwarn' | 'preserveEntrySignatures'
    >
  }
  /**
   * Whether your application is a Single Page Application (SPA),
   * a Multi-Page Application (MPA), or Custom Application (SSR
   * and frameworks with custom HTML handling)
   * @default 'spa'
   */
  appType?: AppType
}

export interface ExperimentalOptions {
  /**
   * Append fake `&lang.(ext)` when queries are specified, to preseve the file extension for following plugins to process.
   *
   * @experimental
   * @default false
   */
  importGlobRestoreExtension?: boolean
  /**
   * Build advanced base options. Allow finegrain contol over assets and public files base
   *
   * @experimental
   */
  buildAdvancedBaseOptions?: BuildAdvancedBaseConfig
  /**
   * Enables support of HMR partial accept via `import.meta.hot.acceptExports`.
   *
   * @experimental
   * @default false
   */
  hmrPartialAccept?: boolean
}

export type ResolvedExperimentalOptions = Required<ExperimentalOptions> & {
  buildAdvancedBaseOptions: ResolvedBuildAdvancedBaseConfig
}

export interface LegacyOptions {
  /**
   * Revert vite dev to the v2.9 strategy. Enable esbuild based deps scanner.
   *
   * @experimental
   * @deprecated
   * @default false
   */
  devDepsScanner?: boolean
  /**
   * Revert vite build to the v2.9 strategy. Disable esbuild deps optimization and adds `@rollup/plugin-commonjs`
   *
   * @experimental
   * @deprecated
   * @default false
   */
  buildRollupPluginCommonjs?: boolean
  /**
   * Revert vite build --ssr to the v2.9 strategy. Use CJS SSR build and v2.9 externalization heuristics
   *
   * @experimental
   * @deprecated
   * @default false
   */
  buildSsrCjsExternalHeuristics?: boolean
}

export interface ResolveWorkerOptions {
  format: 'es' | 'iife'
  plugins: Plugin[]
  rollupOptions: RollupOptions
}

export interface InlineConfig extends UserConfig {
  configFile?: string | false
  envFile?: false
}

export type ResolvedConfig = Readonly<
  Omit<UserConfig, 'plugins' | 'assetsInclude' | 'optimizeDeps' | 'worker'> & {
    configFile: string | undefined
    configFileDependencies: string[]
    inlineConfig: InlineConfig
    root: string
    base: string
    publicDir: string
    cacheDir: string
    command: 'build' | 'serve'
    mode: string
    isWorker: boolean
    // in nested worker bundle to find the main config
    /** @internal */
    mainConfig: ResolvedConfig | null
    isProduction: boolean
    env: Record<string, any>
    resolve: ResolveOptions & {
      alias: Alias[]
    }
    plugins: readonly Plugin[]
    server: ResolvedServerOptions
    build: ResolvedBuildOptions
    preview: ResolvedPreviewOptions
    ssr: ResolvedSSROptions | undefined
    assetsInclude: (file: string) => boolean
    logger: Logger
    createResolver: (options?: Partial<InternalResolveOptions>) => ResolveFn
    optimizeDeps: DepOptimizationOptions
    /** @internal */
    packageCache: PackageCache
    worker: ResolveWorkerOptions
    appType: AppType
    experimental: ResolvedExperimentalOptions
  }
>

export type ResolveFn = (
  id: string,
  importer?: string,
  aliasOnly?: boolean,
  ssr?: boolean
) => Promise<string | undefined>

export async function resolveConfig(
  inlineConfig: InlineConfig,
  command: 'build' | 'serve',
  defaultMode = 'development'
): Promise<ResolvedConfig> {
  let config = inlineConfig
  let configFileDependencies: string[] = []
  let mode = inlineConfig.mode || defaultMode

  // some dependencies e.g. @vue/compiler-* relies on NODE_ENV for getting
  // production-specific behavior, so set it here even though we haven't
  // resolve the final mode yet
  if (mode === 'production') {
    process.env.NODE_ENV = 'production'
  }

  const configEnv = {
    mode,
    command
  }

  let { configFile } = config
  if (configFile !== false) {
    const loadResult = await loadConfigFromFile(
      configEnv,
      configFile,
      config.root,
      config.logLevel
    )
    if (loadResult) {
      config = mergeConfig(loadResult.config, config)
      configFile = loadResult.path
      configFileDependencies = loadResult.dependencies
    }
  }

  // Define logger
  const logger = createLogger(config.logLevel, {
    allowClearScreen: config.clearScreen,
    customLogger: config.customLogger
  })

  // user config may provide an alternative mode. But --mode has a higher priority
  mode = inlineConfig.mode || config.mode || mode
  configEnv.mode = mode

  // resolve plugins
  const rawUserPlugins = (
    (await asyncFlatten(config.plugins || [])) as Plugin[]
  ).filter((p) => {
    if (!p) {
      return false
    } else if (!p.apply) {
      return true
    } else if (typeof p.apply === 'function') {
      return p.apply({ ...config, mode }, configEnv)
    } else {
      return p.apply === command
    }
  })
  const [prePlugins, normalPlugins, postPlugins] =
    sortUserPlugins(rawUserPlugins)

  // resolve worker
  const resolvedWorkerOptions: ResolveWorkerOptions = {
    format: config.worker?.format || 'iife',
    plugins: [],
    rollupOptions: config.worker?.rollupOptions || {}
  }

  // run config hooks
  const userPlugins = [...prePlugins, ...normalPlugins, ...postPlugins]
  for (const p of userPlugins) {
    if (p.config) {
      const res = await p.config(config, configEnv)
      if (res) {
        config = mergeConfig(config, res)
      }
    }
  }

  // resolve root
  const resolvedRoot = normalizePath(
    config.root ? path.resolve(config.root) : process.cwd()
  )

  const clientAlias = [
    { find: /^[\/]?@vite\/env/, replacement: () => ENV_ENTRY },
    { find: /^[\/]?@vite\/client/, replacement: () => CLIENT_ENTRY }
  ]

  // resolve alias with internal client alias
  const resolvedAlias = normalizeAlias(
    mergeAlias(
      // @ts-ignore because @rollup/plugin-alias' type doesn't allow function
      // replacement, but its implementation does work with function values.
      clientAlias,
      config.resolve?.alias || []
    )
  )

  const resolveOptions: ResolvedConfig['resolve'] = {
    ...config.resolve,
    alias: resolvedAlias
  }

  // load .env files
  const envDir = config.envDir
    ? normalizePath(path.resolve(resolvedRoot, config.envDir))
    : resolvedRoot
  const userEnv =
    inlineConfig.envFile !== false &&
    loadEnv(mode, envDir, resolveEnvPrefix(config))

  // Note it is possible for user to have a custom mode, e.g. `staging` where
  // production-like behavior is expected. This is indicated by NODE_ENV=production
  // loaded from `.staging.env` and set by us as VITE_USER_NODE_ENV
  const isProduction =
    (process.env.NODE_ENV || process.env.VITE_USER_NODE_ENV || mode) ===
    'production'
  if (isProduction) {
    // in case default mode was not production and is overwritten
    process.env.NODE_ENV = 'production'
  }

  // resolve public base url
  const isBuild = command === 'build'
  const relativeBaseShortcut = config.base === '' || config.base === './'

  // During dev, we ignore relative base and fallback to '/'
  // For the SSR build, relative base isn't possible by means
  // of import.meta.url. The user will be able to work out a setup
  // using experimental.buildAdvancedBaseOptions
  const base =
    relativeBaseShortcut && (!isBuild || config.build?.ssr)
      ? '/'
      : config.base ?? '/'
  let resolvedBase = relativeBaseShortcut
    ? base
    : resolveBaseUrl(base, isBuild, logger, 'base')
  if (
    config.experimental?.buildAdvancedBaseOptions?.relative &&
    config.base === undefined
  ) {
    resolvedBase = './'
  }

  const resolvedBuildAdvancedBaseOptions = resolveBuildAdvancedBaseConfig(
    config.experimental?.buildAdvancedBaseOptions,
    resolvedBase,
    isBuild,
    logger
  )

  const resolvedBuildOptions = resolveBuildOptions(
    config.build,
    isBuild,
    logger
  )

  // resolve cache directory
  const pkgPath = lookupFile(resolvedRoot, [`package.json`], { pathOnly: true })
  const cacheDir = config.cacheDir
    ? path.resolve(resolvedRoot, config.cacheDir)
    : pkgPath
    ? path.join(path.dirname(pkgPath), `node_modules/.vite`)
    : path.join(resolvedRoot, `.vite`)

  const assetsFilter = config.assetsInclude
    ? createFilter(config.assetsInclude)
    : () => false

  // create an internal resolver to be used in special scenarios, e.g.
  // optimizer & handling css @imports
  const createResolver: ResolvedConfig['createResolver'] = (options) => {
    let aliasContainer: PluginContainer | undefined
    let resolverContainer: PluginContainer | undefined
    return async (id, importer, aliasOnly, ssr) => {
      let container: PluginContainer
      if (aliasOnly) {
        container =
          aliasContainer ||
          (aliasContainer = await createPluginContainer({
            ...resolved,
            plugins: [aliasPlugin({ entries: resolved.resolve.alias })]
          }))
      } else {
        container =
          resolverContainer ||
          (resolverContainer = await createPluginContainer({
            ...resolved,
            plugins: [
              aliasPlugin({ entries: resolved.resolve.alias }),
              resolvePlugin({
                ...resolved.resolve,
                root: resolvedRoot,
                isProduction,
                isBuild: command === 'build',
                ssrConfig: resolved.ssr,
                asSrc: true,
                preferRelative: false,
                tryIndex: true,
                ...options
              })
            ]
          }))
      }
      return (await container.resolveId(id, importer, { ssr }))?.id
    }
  }

  const { publicDir } = config
  const resolvedPublicDir =
    publicDir !== false && publicDir !== ''
      ? path.resolve(
          resolvedRoot,
          typeof publicDir === 'string' ? publicDir : 'public'
        )
      : ''

  const server = resolveServerOptions(resolvedRoot, config.server, logger)
  let ssr = resolveSSROptions(config.ssr)
  if (config.legacy?.buildSsrCjsExternalHeuristics) {
    if (ssr) ssr.format = 'cjs'
    else ssr = { target: 'node', format: 'cjs' }
  }

  const middlewareMode = config?.server?.middlewareMode

  config = mergeConfig(config, externalConfigCompat(config, configEnv))
  const optimizeDeps = config.optimizeDeps || {}

  const BASE_URL = resolvedBase

  const resolved: ResolvedConfig = {
    ...config,
    configFile: configFile ? normalizePath(configFile) : undefined,
    configFileDependencies: configFileDependencies.map((name) =>
      normalizePath(path.resolve(name))
    ),
    inlineConfig,
    root: resolvedRoot,
    base: resolvedBase,
    resolve: resolveOptions,
    publicDir: resolvedPublicDir,
    cacheDir,
    command,
    mode,
    ssr,
    isWorker: false,
    mainConfig: null,
    isProduction,
    plugins: userPlugins,
    server,
    build: resolvedBuildOptions,
    preview: resolvePreviewOptions(config.preview, server),
    env: {
      ...userEnv,
      BASE_URL,
      MODE: mode,
      DEV: !isProduction,
      PROD: isProduction
    },
    assetsInclude(file: string) {
      return DEFAULT_ASSETS_RE.test(file) || assetsFilter(file)
    },
    logger,
    packageCache: new Map(),
    createResolver,
    optimizeDeps: {
      ...optimizeDeps,
      esbuildOptions: {
        preserveSymlinks: config.resolve?.preserveSymlinks,
        ...optimizeDeps.esbuildOptions
      }
    },
    worker: resolvedWorkerOptions,
    appType: config.appType ?? middlewareMode === 'ssr' ? 'custom' : 'spa',
    experimental: {
      importGlobRestoreExtension: false,
      hmrPartialAccept: false,
      ...config.experimental,
      buildAdvancedBaseOptions: resolvedBuildAdvancedBaseOptions
    }
  }

  if (middlewareMode === 'ssr') {
    logger.warn(
      colors.yellow(
        `server.middlewareMode 'ssr' is now deprecated, use server.middlewareMode true and appType 'custom'`
      )
    )
  }
  if (middlewareMode === 'html') {
    logger.warn(
      colors.yellow(
        `server.middlewareMode 'html' is now deprecated, use server.middlewareMode true`
      )
    )
  }

  if (resolved.legacy?.buildRollupPluginCommonjs) {
    const optimizerDisabled = resolved.optimizeDeps.disabled
    if (!optimizerDisabled) {
      resolved.optimizeDeps.disabled = 'build'
    } else if (optimizerDisabled === 'dev') {
      resolved.optimizeDeps.disabled = true // Also disabled during build
    }
  }

  // Some plugins that aren't intended to work in the bundling of workers (doing post-processing at build time for example).
  // And Plugins may also have cached that could be corrupted by being used in these extra rollup calls.
  // So we need to separate the worker plugin from the plugin that vite needs to run.
  const [workerPrePlugins, workerNormalPlugins, workerPostPlugins] =
    sortUserPlugins(config.worker?.plugins as Plugin[])
  const workerResolved: ResolvedConfig = {
    ...resolved,
    isWorker: true,
    mainConfig: resolved
  }
  resolved.worker.plugins = await resolvePlugins(
    workerResolved,
    workerPrePlugins,
    workerNormalPlugins,
    workerPostPlugins
  )
  // call configResolved worker plugins hooks
  await Promise.all(
    resolved.worker.plugins.map((p) => p.configResolved?.(workerResolved))
  )
  ;(resolved.plugins as Plugin[]) = await resolvePlugins(
    resolved,
    prePlugins,
    normalPlugins,
    postPlugins
  )

  // call configResolved hooks
  await Promise.all(userPlugins.map((p) => p.configResolved?.(resolved)))

  if (process.env.DEBUG) {
    debug(`using resolved config: %O`, {
      ...resolved,
      plugins: resolved.plugins.map((p) => p.name)
    })
  }

  if (config.build?.terserOptions && config.build.minify !== 'terser') {
    logger.warn(
      colors.yellow(
        `build.terserOptions is specified but build.minify is not set to use Terser. ` +
          `Note Vite now defaults to use esbuild for minification. If you still ` +
          `prefer Terser, set build.minify to "terser".`
      )
    )
  }

  // Check if all assetFileNames have the same reference.
  // If not, display a warn for user.
  const outputOption = config.build?.rollupOptions?.output ?? []
  // Use isArray to narrow its type to array
  if (Array.isArray(outputOption)) {
    const assetFileNamesList = outputOption.map(
      (output) => output.assetFileNames
    )
    if (assetFileNamesList.length > 1) {
      const firstAssetFileNames = assetFileNamesList[0]
      const hasDifferentReference = assetFileNamesList.some(
        (assetFileNames) => assetFileNames !== firstAssetFileNames
      )
      if (hasDifferentReference) {
        resolved.logger.warn(
          colors.yellow(`
assetFileNames isn't equal for every build.rollupOptions.output. A single pattern across all outputs is supported by Vite.
`)
        )
      }
    }
  }

  return resolved
}

/**
 * Resolve base url. Note that some users use Vite to build for non-web targets like
 * electron or expects to deploy
 */
export function resolveBaseUrl(
  base: UserConfig['base'] = '/',
  isBuild: boolean,
  logger: Logger,
  optionName: string
): string {
  if (base.startsWith('.')) {
    logger.warn(
      colors.yellow(
        colors.bold(
          `(!) invalid "${optionName}" option: ${base}. The value can only be an absolute ` +
            `URL, ./, or an empty string.`
        )
      )
    )
    base = '/'
  }

  // external URL
  if (isExternalUrl(base)) {
    if (!isBuild) {
      // get base from full url during dev
      const parsed = parseUrl(base)
      base = parsed.pathname || '/'
    }
  } else {
    // ensure leading slash
    if (!base.startsWith('/')) {
      logger.warn(
        colors.yellow(
          colors.bold(`(!) "${optionName}" option should start with a slash.`)
        )
      )
      base = '/' + base
    }
  }

  // ensure ending slash
  if (!base.endsWith('/')) {
    logger.warn(
      colors.yellow(
        colors.bold(`(!) "${optionName}" option should end with a slash.`)
      )
    )
    base += '/'
  }

  return base
}

export function sortUserPlugins(
  plugins: (Plugin | Plugin[])[] | undefined
): [Plugin[], Plugin[], Plugin[]] {
  const prePlugins: Plugin[] = []
  const postPlugins: Plugin[] = []
  const normalPlugins: Plugin[] = []

  if (plugins) {
    plugins.flat().forEach((p) => {
      if (p.enforce === 'pre') prePlugins.push(p)
      else if (p.enforce === 'post') postPlugins.push(p)
      else normalPlugins.push(p)
    })
  }

  return [prePlugins, normalPlugins, postPlugins]
}

export async function loadConfigFromFile(
  configEnv: ConfigEnv,
  configFile?: string,
  configRoot: string = process.cwd(),
  logLevel?: LogLevel
): Promise<{
  path: string
  config: UserConfig
  dependencies: string[]
} | null> {
  const start = performance.now()
  const getTime = () => `${(performance.now() - start).toFixed(2)}ms`

  let resolvedPath: string | undefined
  let dependencies: string[] = []

  if (configFile) {
    // explicit config path is always resolved from cwd
    resolvedPath = path.resolve(configFile)
  } else {
    // implicit config file loaded from inline root (if present)
    // otherwise from cwd
    for (const filename of DEFAULT_CONFIG_FILES) {
      const filePath = path.resolve(configRoot, filename)
      if (!fs.existsSync(filePath)) continue

      resolvedPath = filePath
      break
    }
  }

  if (!resolvedPath) {
    debug('no config file found.')
    return null
  }

  let isESM = false
  if (/\.m[jt]s$/.test(resolvedPath)) {
    isESM = true
  } else if (/\.c[jt]s$/.test(resolvedPath)) {
    isESM = false
  } else {
    // check package.json for type: "module" and set `isESM` to true
    try {
      const pkg = lookupFile(configRoot, ['package.json'])
      isESM = !!pkg && JSON.parse(pkg).type === 'module'
    } catch (e) {}
  }

  try {
    let userConfig: UserConfigExport | undefined

    if (isESM) {
      const fileUrl = pathToFileURL(resolvedPath)
      const bundled = await bundleConfigFile(resolvedPath, true)
      dependencies = bundled.dependencies

      if (isTS(resolvedPath)) {
        // before we can register loaders without requiring users to run node
        // with --experimental-loader themselves, we have to do a hack here:
        // bundle the config file w/ ts transforms first, write it to disk,
        // load it with native Node ESM, then delete the file.
        fs.writeFileSync(resolvedPath + '.mjs', bundled.code)
        userConfig = (await dynamicImport(`${fileUrl}.mjs?t=${Date.now()}`))
          .default
        fs.unlinkSync(resolvedPath + '.mjs')
        debug(`TS + native esm config loaded in ${getTime()}`, fileUrl)
      } else {
        // using Function to avoid this from being compiled away by TS/Rollup
        // append a query so that we force reload fresh config in case of
        // server restart
        userConfig = (await dynamicImport(`${fileUrl}?t=${Date.now()}`)).default
        debug(`native esm config loaded in ${getTime()}`, fileUrl)
      }
    }

    if (!userConfig) {
      // Bundle config file and transpile it to cjs using esbuild.
      const bundled = await bundleConfigFile(resolvedPath)
      dependencies = bundled.dependencies
      userConfig = await loadConfigFromBundledFile(resolvedPath, bundled.code)
      debug(`bundled config file loaded in ${getTime()}`)
    }

    const config = await (typeof userConfig === 'function'
      ? userConfig(configEnv)
      : userConfig)
    if (!isObject(config)) {
      throw new Error(`config must export or return an object.`)
    }
    return {
      path: normalizePath(resolvedPath),
      config,
      dependencies
    }
  } catch (e) {
    createLogger(logLevel).error(
      colors.red(`failed to load config from ${resolvedPath}`),
      { error: e }
    )
    throw e
  }
}

async function bundleConfigFile(
  fileName: string,
  isESM = false
): Promise<{ code: string; dependencies: string[] }> {
  const importMetaUrlVarName = '__vite_injected_original_import_meta_url'
  const result = await build({
    absWorkingDir: process.cwd(),
    entryPoints: [fileName],
    outfile: 'out.js',
    write: false,
    platform: 'node',
    bundle: true,
    format: isESM ? 'esm' : 'cjs',
    sourcemap: 'inline',
    metafile: true,
    define: {
      'import.meta.url': importMetaUrlVarName
    },
    plugins: [
      {
        name: 'externalize-deps',
        setup(build) {
          build.onResolve({ filter: /.*/ }, (args) => {
            const id = args.path
            if (id[0] !== '.' && !path.isAbsolute(id)) {
              return {
                external: true
              }
            }
          })
        }
      },
      {
        name: 'inject-file-scope-variables',
        setup(build) {
          build.onLoad({ filter: /\.[cm]?[jt]s$/ }, async (args) => {
            const contents = await fs.promises.readFile(args.path, 'utf8')
            const injectValues =
              `const __dirname = ${JSON.stringify(path.dirname(args.path))};` +
              `const __filename = ${JSON.stringify(args.path)};` +
              `const ${importMetaUrlVarName} = ${JSON.stringify(
                pathToFileURL(args.path).href
              )};`

            return {
              loader: isTS(args.path) ? 'ts' : 'js',
              contents: injectValues + contents
            }
          })
        }
      }
    ]
  })
  const { text } = result.outputFiles[0]
  return {
    code: text,
    dependencies: result.metafile ? Object.keys(result.metafile.inputs) : []
  }
}

interface NodeModuleWithCompile extends NodeModule {
  _compile(code: string, filename: string): any
}

const _require = createRequire(import.meta.url)
async function loadConfigFromBundledFile(
  fileName: string,
  bundledCode: string
): Promise<UserConfig> {
  const realFileName = fs.realpathSync(fileName)
  const defaultLoader = _require.extensions['.js']
  _require.extensions['.js'] = (module: NodeModule, filename: string) => {
    if (filename === realFileName) {
      ;(module as NodeModuleWithCompile)._compile(bundledCode, filename)
    } else {
      defaultLoader(module, filename)
    }
  }
  // clear cache in case of server restart
  delete _require.cache[_require.resolve(fileName)]
  const raw = _require(fileName)
  _require.extensions['.js'] = defaultLoader
  return raw.__esModule ? raw.default : raw
}

export function isDepsOptimizerEnabled(config: ResolvedConfig): boolean {
  const { command, optimizeDeps } = config
  const { disabled } = optimizeDeps
  return !(
    disabled === true ||
    (command === 'build' && disabled === 'build') ||
    (command === 'serve' && optimizeDeps.disabled === 'dev')
  )
}

// esbuild doesn't transpile `require('foo')` into `import` statements if 'foo' is externalized
// https://github.com/evanw/esbuild/issues/566#issuecomment-735551834
function esbuildCjsExternalPlugin(externals: string[]): ESBuildPlugin {
  return {
    name: 'cjs-external',
    setup(build) {
      const escape = (text: string) =>
        `^${text.replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&')}$`
      const filter = new RegExp(externals.map(escape).join('|'))

      build.onResolve({ filter: /.*/, namespace: 'external' }, (args) => ({
        path: args.path,
        external: true
      }))

      build.onResolve({ filter }, (args) => ({
        path: args.path,
        namespace: 'external'
      }))

      build.onLoad({ filter: /.*/, namespace: 'external' }, (args) => ({
        contents: `export * from ${JSON.stringify(args.path)}`
      }))
    }
  }
}

// Support `rollupOptions.external` when `legacy.buildRollupPluginCommonjs` is disabled
function externalConfigCompat(config: UserConfig, { command }: ConfigEnv) {
  // Only affects the build command
  if (command !== 'build') {
    return {}
  }

  // Skip if using Rollup CommonJS plugin
  if (
    config.legacy?.buildRollupPluginCommonjs ||
    config.optimizeDeps?.disabled === 'build'
  ) {
    return {}
  }

  // Skip if no `external` configured
  const external = config?.build?.rollupOptions?.external
  if (!external) {
    return {}
  }

  let normalizedExternal = external
  if (typeof external === 'string') {
    normalizedExternal = [external]
  }

  // TODO: decide whether to support RegExp and function options
  // They're not supported yet because `optimizeDeps.exclude` currently only accepts strings
  if (
    !Array.isArray(normalizedExternal) ||
    normalizedExternal.some((ext) => typeof ext !== 'string')
  ) {
    throw new Error(
      `[vite] 'build.rollupOptions.external' can only be an array of strings or a string.\n` +
        `You can turn on 'legacy.buildRollupPluginCommonjs' to support more advanced options.`
    )
  }

  const additionalConfig: UserConfig = {
    optimizeDeps: {
      exclude: normalizedExternal as string[],
      esbuildOptions: {
        plugins: [
          // TODO: maybe it can be added globally/unconditionally?
          esbuildCjsExternalPlugin(normalizedExternal as string[])
        ]
      }
    }
  }

  return additionalConfig
}