tree-shaking/misleading warning "module has been externalized for browser compatibility"

[samuelstroschein]

Describe the bug

Vite emits a build warning if a node API is imported even though the code is never bundled for the client.

Blocks this issue in Paraglide JS. #5676 is likely related.

Reproduction

https://stackblitz.com/edit/vitejs-vite-4ugmukbe?file=src%2Fmain.js

Steps to reproduce

Run npm install && npm run build.

The serverMiddleware code is never imported in the client-side code. Yet, Vite emits the build warning.

async function serverMiddleware() {
  const { AsyncLocalStorage } = await import('async_hooks');
  console.log(AsyncLocalStorage);
}

System Info

Stackblitz

Used Package Manager

npm

Logs

❯ vite build --debug
vite:config no config file found. +0ms
vite:config using resolved config: {
vite:config root: '/home/projects/vitejs-vite-4ugmukbe',
vite:config base: '/',
vite:config mode: 'production',
vite:config configFile: undefined,
vite:config configLoader: undefined,
vite:config logLevel: undefined,
vite:config clearScreen: undefined,
vite:config build: {
vite:config target: [ 'es2020', 'edge88', 'firefox78', 'chrome87', 'safari14' ],
vite:config polyfillModulePreload: true,
vite:config modulePreload: { polyfill: true },
vite:config outDir: 'dist',
vite:config assetsDir: 'assets',
vite:config assetsInlineLimit: 4096,
vite:config sourcemap: false,
vite:config terserOptions: {},
vite:config rollupOptions: {},
vite:config commonjsOptions: { include: [ /node_modules/ ], extensions: [ '.js', '.cjs' ] },
vite:config dynamicImportVarsOptions: { warnOnError: true, exclude: [ /node_modules/ ] },
vite:config write: true,
vite:config emptyOutDir: null,
vite:config copyPublicDir: true,
vite:config manifest: false,
vite:config lib: false,
vite:config ssrManifest: false,
vite:config ssrEmitAssets: false,
vite:config reportCompressedSize: true,
vite:config chunkSizeWarningLimit: 500,
vite:config watch: null,
vite:config cssCodeSplit: true,
vite:config minify: 'esbuild',
vite:config ssr: false,
vite:config emitAssets: true,
vite:config createEnvironment: [Function: createEnvironment],
vite:config cssTarget: [ 'es2020', 'edge88', 'firefox78', 'chrome87', 'safari14' ],
vite:config cssMinify: true
vite:config },
vite:config environments: {
vite:config client: {
vite:config define: undefined,
vite:config resolve: {
vite:config externalConditions: [ 'node' ],
vite:config extensions: [ '.mjs', '.js', '.ts', '.jsx', '.tsx', '.json' ],
vite:config dedupe: [],
vite:config noExternal: [],
vite:config external: [],
vite:config preserveSymlinks: false,
vite:config alias: [
vite:config {
vite:config find: /^/?@vite/env/,
vite:config replacement: '/@fs/home/projects/vitejs-vite-4ugmukbe/node_modules/vite/dist/client/env.mjs'
vite:config },
vite:config {
vite:config find: /^/?@vite/client/,
vite:config replacement: '/@fs/home/projects/vitejs-vite-4ugmukbe/node_modules/vite/dist/client/client.mjs'
vite:config }
vite:config ],
vite:config mainFields: [ 'browser', 'module', 'jsnext:main', 'jsnext' ],
vite:config conditions: [ 'module', 'browser', 'development|production' ],
vite:config builtins: []
vite:config },
vite:config keepProcessEnv: false,
vite:config consumer: 'client',
vite:config optimizeDeps: {
vite:config include: [],
vite:config exclude: [],
vite:config needsInterop: [],
vite:config extensions: [],
vite:config disabled: undefined,
vite:config holdUntilCrawlEnd: true,
vite:config force: false,
vite:config noDiscovery: false,
vite:config esbuildOptions: { preserveSymlinks: false }
vite:config },
vite:config dev: {
vite:config warmup: [],
vite:config sourcemap: { js: true },
vite:config sourcemapIgnoreList: [Function: isInNodeModules$1],
vite:config preTransformRequests: true,
vite:config createEnvironment: [Function: defaultCreateClientDevEnvironment],
vite:config recoverable: true,
vite:config moduleRunnerTransform: false
vite:config },
vite:config build: {
vite:config target: [ 'es2020', 'edge88', 'firefox78', 'chrome87', 'safari14' ],
vite:config polyfillModulePreload: true,
vite:config modulePreload: { polyfill: true },
vite:config outDir: 'dist',
vite:config assetsDir: 'assets',
vite:config assetsInlineLimit: 4096,
vite:config sourcemap: false,
vite:config terserOptions: {},
vite:config rollupOptions: {},
vite:config commonjsOptions: { include: [ /node_modules/ ], extensions: [ '.js', '.cjs' ] },
vite:config dynamicImportVarsOptions: { warnOnError: true, exclude: [ /node_modules/ ] },
vite:config write: true,
vite:config emptyOutDir: null,
vite:config copyPublicDir: true,
vite:config manifest: false,
vite:config lib: false,
vite:config ssrManifest: false,
vite:config ssrEmitAssets: false,
vite:config reportCompressedSize: true,
vite:config chunkSizeWarningLimit: 500,
vite:config watch: null,
vite:config cssCodeSplit: true,
vite:config minify: 'esbuild',
vite:config ssr: false,
vite:config emitAssets: true,
vite:config createEnvironment: [Function: createEnvironment],
vite:config cssTarget: [ 'es2020', 'edge88', 'firefox78', 'chrome87', 'safari14' ],
vite:config cssMinify: true
vite:config }
vite:config }
vite:config },
vite:config resolve: {
vite:config externalConditions: [ 'node' ],
vite:config extensions: [ '.mjs', '.js', '.ts', '.jsx', '.tsx', '.json' ],
vite:config dedupe: [],
vite:config noExternal: [],
vite:config external: [],
vite:config preserveSymlinks: false,
vite:config alias: [
vite:config {
vite:config find: /^/?@vite/env/,
vite:config replacement: '/@fs/home/projects/vitejs-vite-4ugmukbe/node_modules/vite/dist/client/env.mjs'
vite:config },
vite:config {
vite:config find: /^/?@vite/client/,
vite:config replacement: '/@fs/home/projects/vitejs-vite-4ugmukbe/node_modules/vite/dist/client/client.mjs'
vite:config }
vite:config ],
vite:config mainFields: [ 'browser', 'module', 'jsnext:main', 'jsnext' ],
vite:config conditions: [ 'module', 'browser', 'development|production' ],
vite:config builtins: []
vite:config },
vite:config configFileDependencies: [],
vite:config inlineConfig: {
vite:config root: undefined,
vite:config base: undefined,
vite:config mode: undefined,
vite:config configFile: undefined,
vite:config configLoader: undefined,
vite:config logLevel: undefined,
vite:config clearScreen: undefined,
vite:config build: {},
vite:config environments: {
vite:config client: {
vite:config define: undefined,
vite:config resolve: undefined,
vite:config dev: {},
vite:config build: {},
vite:config optimizeDeps: undefined
vite:config }
vite:config },
vite:config resolve: { conditions: undefined, mainFields: undefined }
vite:config },
vite:config decodedBase: '/',
vite:config rawBase: '/',
vite:config publicDir: '/home/projects/vitejs-vite-4ugmukbe/public',
vite:config cacheDir: '/home/projects/vitejs-vite-4ugmukbe/node_modules/.vite',
vite:config command: 'build',
vite:config isWorker: false,
vite:config mainConfig: null,
vite:config bundleChain: [],
vite:config isProduction: true,
vite:config plugins: [
vite:config 'vite:build-metadata',
vite:config 'vite:watch-package-data',
vite:config 'vite:pre-alias',
vite:config 'alias',
vite:config 'vite:modulepreload-polyfill',
vite:config 'vite:resolve',
vite:config 'vite:html-inline-proxy',
vite:config 'vite:css',
vite:config 'vite:esbuild',
vite:config 'vite:json',
vite:config 'vite:wasm-helper',
vite:config 'vite:worker',
vite:config 'vite:asset',
vite:config 'vite:wasm-fallback',
vite:config 'vite:define',
vite:config 'vite:css-post',
vite:config 'vite:build-html',
vite:config 'vite:worker-import-meta-url',
vite:config 'vite:asset-import-meta-url',
vite:config 'vite:force-systemjs-wrap-complete',
vite:config 'commonjs',
vite:config 'vite:data-uri',
vite:config 'vite:rollup-options-plugins',
vite:config 'vite:dynamic-import-vars',
vite:config 'vite:import-glob',
vite:config 'vite:build-import-analysis',
vite:config 'vite:esbuild-transpile',
vite:config 'vite:terser',
vite:config 'vite:manifest',
vite:config 'vite:ssr-manifest',
vite:config 'vite:reporter',
vite:config 'vite:load-fallback'
vite:config ],
vite:config css: {
vite:config transformer: 'postcss',
vite:config preprocessorMaxWorkers: 0,
vite:config devSourcemap: false,
vite:config lightningcss: undefined
vite:config },
vite:config json: { namedExports: true, stringify: 'auto' },
vite:config esbuild: { jsxDev: false },
vite:config server: {
vite:config port: 5173,
vite:config strictPort: false,
vite:config host: undefined,
vite:config allowedHosts: [],
vite:config https: undefined,
vite:config open: false,
vite:config proxy: undefined,
vite:config cors: {
vite:config origin: /^https?://(?:(?:[^:]+.)?localhost|127.0.0.1|[::1])(?::\d+)?$/
vite:config },
vite:config headers: {},
vite:config warmup: { clientFiles: [], ssrFiles: [] },
vite:config middlewareMode: false,
vite:config fs: {
vite:config strict: true,
vite:config deny: [ '.env', '.env.', '.{crt,pem}', '/.git/' ],
vite:config allow: [ '/home/projects/vitejs-vite-4ugmukbe' ]
vite:config },
vite:config preTransformRequests: true,
vite:config perEnvironmentStartEndDuringDev: false,
vite:config sourcemapIgnoreList: [Function: isInNodeModules$1]
vite:config },
vite:config builder: undefined,
vite:config preview: {
vite:config port: 4173,
vite:config strictPort: false,
vite:config host: undefined,
vite:config allowedHosts: [],
vite:config https: undefined,
vite:config open: false,
vite:config proxy: undefined,
vite:config cors: {
vite:config origin: /^https?://(?:(?:[^:]+.)?localhost|127.0.0.1|[::1])(?::\d+)?$/
vite:config },
vite:config headers: {}
vite:config },
vite:config envDir: '/home/projects/vitejs-vite-4ugmukbe',
vite:config env: { BASE_URL: '/', MODE: 'production', DEV: false, PROD: true },
vite:config assetsInclude: [Function: assetsInclude],
vite:config logger: {
vite:config hasWarned: false,
vite:config info: [Function: info],
vite:config warn: [Function: warn],
vite:config warnOnce: [Function: warnOnce],
vite:config error: [Function: error],
vite:config clearScreen: [Function: clearScreen],
vite:config hasErrorLogged: [Function: hasErrorLogged]
vite:config },
vite:config packageCache: Map(1) {
vite:config 'fnpd_/home/projects/vitejs-vite-4ugmukbe' => {
vite:config dir: '/home/projects/vitejs-vite-4ugmukbe',
vite:config data: {
vite:config name: 'vite-starter',
vite:config private: true,
vite:config version: '0.0.0',
vite:config type: 'module',
vite:config scripts: { dev: 'vite', build: 'vite build', preview: 'vite preview' },
vite:config devDependencies: { vite: '^6.1.0' }
vite:config },
vite:config hasSideEffects: [Function: hasSideEffects],
vite:config setResolvedCache: [Function: setResolvedCache],
vite:config getResolvedCache: [Function: getResolvedCache]
vite:config },
vite:config set: [Function (anonymous)]
vite:config },
vite:config worker: { format: 'iife', plugins: '() => plugins', rollupOptions: {} },
vite:config appType: 'spa',
vite:config experimental: { importGlobRestoreExtension: false, hmrPartialAccept: false },
vite:config future: undefined,
vite:config ssr: {
vite:config target: 'node',
vite:config optimizeDeps: { esbuildOptions: { preserveSymlinks: false } },
vite:config resolve: { conditions: undefined, externalConditions: undefined }
vite:config },
vite:config optimizeDeps: {
vite:config include: [],
vite:config exclude: [],
vite:config needsInterop: [],
vite:config extensions: [],
vite:config disabled: undefined,
vite:config holdUntilCrawlEnd: true,
vite:config force: false,
vite:config noDiscovery: false,
vite:config esbuildOptions: { preserveSymlinks: false }
vite:config },
vite:config dev: {
vite:config warmup: [],
vite:config sourcemap: { js: true },
vite:config sourcemapIgnoreList: [Function: isInNodeModules$1],
vite:config preTransformRequests: false,
vite:config createEnvironment: [Function: defaultCreateDevEnvironment],
vite:config recoverable: false,
vite:config moduleRunnerTransform: false
vite:config },
vite:config webSocketToken: 'TWOW0F5ledRQ',
vite:config getSortedPlugins: [Function: getSortedPlugins],
vite:config getSortedPluginHooks: [Function: getSortedPluginHooks],
vite:config createResolver: [Function: createResolver],
vite:config fsDenyGlob: [Function: arrayMatcher],
vite:config safeModulePaths: Set(0) {},
vite:config additionalAllowedHosts: []
vite:config } +9ms
vite v6.1.1 building for production...
[plugin vite:resolve] Module "async_hooks" has been externalized for browser compatibility, imported by "/home/projects/vitejs-vite-4ugmukbe/src/main.js". See https://vite.dev/guide/troubleshooting.html#module-externalized-for-browser-compatibility for more details.
✓ 9 modules transformed.
dist/index.html 0.45 kB │ gzip: 0.29 kB
dist/assets/index-CrYBktwj.css 1.20 kB │ gzip: 0.62 kB
dist/assets/index-_AYE_jbl.js 2.58 kB │ gzip: 1.37 kB
✓ built in 563ms

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