Missing "." export in "package-name" package

[sibbng]

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Describe the bug

Hi, I'm currently working on https://github.com/antfu/reactivue/tree/b48200b9b0c5c2e02cf7855e1568f11c808de43c tree.
Using build of this tree in react-ts template. Running vite dev is fine but vite build prompts an error on console. This issue occurs on 2.0.0-beta.23. I tested it on 2.0.0-beta.21, it works fine.

System Info

• vite version: 2.0.0-beta.23
• Operating System: Windows 10
• Node version: v12.16.2
• Package manager (npm/yarn/pnpm) and version: yarn

Logs (Optional if provided reproduction)

$ vite build --debug
  vite:config bundled config file loaded in 143ms +0ms
  vite:config using resolved config: {
  vite:config   plugins: [
  vite:config     'alias',
  vite:config     'vite:dynamic-import-polyfill',
  vite:config     'vite:resolve',
  vite:config     'vite:html',
  vite:config     'vite:css',
  vite:config     'vite:esbuild',
  vite:config     'vite:json',
  vite:config     'vite:wasm',
  vite:config     'vite:worker',
  vite:config     'vite:asset',
  vite:config     'react-refresh',
  vite:config     'vite:css-post',
  vite:config     'vite:build-html',
  vite:config     'commonjs',
  vite:config     'vite:data-uri',
  vite:config     'vite:define',
  vite:config     'rollup-plugin-dynamic-import-variables',
  vite:config     'vite:import-analysis',
  vite:config     'vite:esbuild-transpile',
  vite:config     'vite:terser',
  vite:config     'vite:size'
  vite:config   ],
  vite:config   alias: [
  vite:config     {
  vite:config       find: /^\/@vite\//,
  vite:config       replacement: 'C:\\Users\\sib\\Desktop\\dev\\vite-project-react\\node_modules\\vite\\dist\\client/'
  vite:config     },
  vite:config     { find: 'vue', replacement: 'reactivue' },
  vite:config     { find: '@vue/runtime-dom', replacement: 'reactivue' }
  vite:config   ],
  vite:config   optimizeDeps: { exclude: [ '@vue/reactivity' ] },
  vite:config   build: {
  vite:config     base: '/',
  vite:config     target: [ 'es2019', 'edge16', 'firefox60', 'chrome61', 'safari11' ],
  vite:config     polyfillDynamicImport: true,
  vite:config     outDir: 'dist',
  vite:config     assetsDir: 'assets',
  vite:config     assetsInlineLimit: 4096,
  vite:config     cssCodeSplit: true,
  vite:config     sourcemap: false,
  vite:config     rollupOptions: {},
  vite:config     commonjsOptions: { include: [Array], extensions: [Array] },
  vite:config     minify: 'terser',
  vite:config     terserOptions: {},
  vite:config     cleanCssOptions: {},
  vite:config     write: true,
  vite:config     manifest: false,
  vite:config     lib: false,
  vite:config     ssr: false
  vite:config   },
  vite:config   configFile: '/Users/sib/Desktop/dev/vite-project-react/vite.config.ts',
  vite:config   inlineConfig: {
  vite:config     root: undefined,
  vite:config     mode: undefined,
  vite:config     configFile: undefined,
  vite:config     logLevel: undefined,
  vite:config     build: {}
  vite:config   },
  vite:config   root: '/Users/sib/Desktop/dev/vite-project-react',
  vite:config   command: 'build',
  vite:config   mode: 'production',
  vite:config   isProduction: true,
  vite:config   optimizeCacheDir: '\\Users\\sib\\Desktop\\dev\\vite-project-react\\node_modules\\.vite',
  vite:config   server: {},
  vite:config   env: { BASE_URL: '/', MODE: 'production', DEV: false, PROD: true },
  vite:config   assetsInclude: [Function: assetsInclude],
  vite:config   logger: {
  vite:config     info: [Function: info],
  vite:config     warn: [Function: warn],
  vite:config     error: [Function: error],
  vite:config     clearScreen: [Function: clearScreen]
  vite:config   }
  vite:config } +6ms
building for production...
[vite:resolve] Missing "." export in "reactivue" package
error during build:
Error: Missing "." export in "reactivue" package
    at bail (C:\Users\sib\Desktop\dev\vite-project-react\node_modules\vite\dist\node\chunks\dep-478c65b9.js:39770:8)
    at resolve$1 (C:\Users\sib\Desktop\dev\vite-project-react\node_modules\vite\dist\node\chunks\dep-478c65b9.js:39846:10)
    at resolveExports (C:\Users\sib\Desktop\dev\vite-project-react\node_modules\vite\dist\node\chunks\dep-478c65b9.js:39852:12)
    at resolvePackageEntry (C:\Users\sib\Desktop\dev\vite-project-react\node_modules\vite\dist\node\chunks\dep-478c65b9.js:40126:22)
    at tryNodeResolve (C:\Users\sib\Desktop\dev\vite-project-react\node_modules\vite\dist\node\chunks\dep-478c65b9.js:40041:11)
    at Object.resolveId (C:\Users\sib\Desktop\dev\vite-project-react\node_modules\vite\dist\node\chunks\dep-478c65b9.js:39952:28)
    at C:\Users\sib\Desktop\dev\vite-project-react\node_modules\rollup\dist\shared\rollup.js:18781:25
    at processTicksAndRejections (internal/process/task_queues.js:97:5)
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

[yyx990803]

This is the correct behavior. When exports field is present, it means anything not explicitly listed inside is not exposed. This should be fixed on reactivue's side by adding . in exports.

Note exports is not an optional addition. Once it's used, modern bundlers and Node.js will prioritize it over everything else, so it must be declared correctly.

[benmccann]

In the case of reactivue, which this issue was originally filed for, it was a bad package configuration. However, typically when I've seen this issue hit it's because of what I'd consider a bug in Vite. Some packages like Firebase legitimately don't have . as an entry point. However, Vite always tries to resolve . instead of whatever entry point the application code is using causing this failure. See #4425 for more details