import.meta.env.MODE=production while import.meta.env.PROD returned false

Describe the bug

When I set NODE_ENV=development in .env file, and set NODE_ENV=production in .env.production file, then run vite build with production mode(by default), the import.meta.env.PROD variable turned out to be false, which is expected to be true.

I found that at vite/packages/vite/src/node/config.ts, there is a loadEnv function, in which process.env.VITE_USER_NODE_ENV would be override by .env file

https://github.com/vitejs/vite/blob/d856c4bd6798707e0cbdfc127a2e8b6c00c65dae/packages/vite/src/node/config.ts#L1012-L1023

https://github.com/vitejs/vite/blob/d856c4bd6798707e0cbdfc127a2e8b6c00c65dae/packages/vite/src/node/config.ts#L353

when vite build, isProduction would be false.

In this case, I think maybe change the condition below may work:

// change this
if (key === 'NODE_ENV') { xxx }
// to
if (key === 'NODE_ENV' && process.env.VITE_USER_NODE_ENV === undefined) { xxx }

Reproduction

https://github.com/RainKolwa/reproduce-vite-env

System Info

System:
    OS: macOS 12.1
    CPU: (8) x64 Intel(R) Core(TM) i5-8257U CPU @ 1.40GHz
    Memory: 115.40 MB / 8.00 GB
    Shell: 3.1.2 - /usr/local/bin/fish
  Binaries:
    Node: 14.17.5 - ~/.nvm/versions/node/v14.17.5/bin/node
    Yarn: 1.22.5 - /usr/local/bin/yarn
    npm: 6.14.14 - ~/.nvm/versions/node/v14.17.5/bin/npm
  Browsers:
    Chrome: 96.0.4664.110
    Firefox: 92.0
    Safari: 15.2
  npmPackages:
    @vitejs/plugin-vue: ^2.0.0 => 2.0.1
    vite: ^2.7.2 => 2.7.9

Used Package Manager

pnpm

Logs

vite:config bundled config file loaded in 64.31ms +0ms
[dotenv][DEBUG] did not match key and value when parsing line 2:
  vite:config using resolved config: {
  vite:config   plugins: [
  vite:config     'alias',
  vite:config     'vite:modulepreload-polyfill',
  vite:config     'vite:resolve',
  vite:config     'vite:html-inline-script-proxy',
  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     'vite:vue',
  vite:config     'vite:define',
  vite:config     'vite:css-post',
  vite:config     'vite:watch-package-data',
  vite:config     'vite:build-html',
  vite:config     'commonjs',
  vite:config     'vite:data-uri',
  vite:config     'rollup-plugin-dynamic-import-variables',
  vite:config     'vite:asset-import-meta-url',
  vite:config     'vite:build-import-analysis',
  vite:config     'vite:esbuild-transpile',
  vite:config     'vite:reporter',
  vite:config     'vite:load-fallback'
  vite:config   ],
  vite:config   server: { open: true, fs: { strict: true, allow: [Array], deny: [Array] } },
  vite:config   build: {
  vite:config     target: [ 'es2019', 'edge88', 'firefox78', 'chrome87', 'safari13.1' ],
  vite:config     polyfillModulePreload: true,
  vite:config     outDir: '/Users/rainkolwa/Personal/reproduce-vite-env/dist',
  vite:config     assetsDir: 'assets',
  vite:config     assetsInlineLimit: 4096,
  vite:config     cssCodeSplit: true,
  vite:config     cssTarget: [ 'es2019', 'edge88', 'firefox78', 'chrome87', 'safari13.1' ],
  vite:config     sourcemap: false,
  vite:config     rollupOptions: {
  vite:config       input: '/Users/rainkolwa/Personal/reproduce-vite-env/index.html'
  vite:config     },
  vite:config     minify: 'esbuild',
  vite:config     terserOptions: {},
  vite:config     write: true,
  vite:config     emptyOutDir: null,
  vite:config     manifest: false,
  vite:config     lib: false,
  vite:config     ssr: false,
  vite:config     ssrManifest: false,
  vite:config     reportCompressedSize: true,
  vite:config     chunkSizeWarningLimit: 500,
  vite:config     watch: null,
  vite:config     commonjsOptions: { include: [Array], extensions: [Array] },
  vite:config     dynamicImportVarsOptions: { warnOnError: true, exclude: [Array] }
  vite:config   },
  vite:config   define: { __VUE_OPTIONS_API__: true, __VUE_PROD_DEVTOOLS__: false },
  vite:config   ssr: { external: [ 'vue', '@vue/server-renderer' ] },
  vite:config   configFile: '/Users/rainkolwa/Personal/reproduce-vite-env/vite.config.js',
  vite:config   configFileDependencies: [ 'vite.config.js' ],
  vite:config   inlineConfig: {
  vite:config     root: undefined,
  vite:config     base: undefined,
  vite:config     mode: undefined,
  vite:config     configFile: undefined,
  vite:config     logLevel: undefined,
  vite:config     clearScreen: undefined,
  vite:config     build: {}
  vite:config   },
  vite:config   root: '/Users/rainkolwa/Personal/reproduce-vite-env',
  vite:config   base: '/',
  vite:config   resolve: { dedupe: undefined, alias: [ [Object], [Object] ] },
  vite:config   publicDir: '/Users/rainkolwa/Personal/reproduce-vite-env/public',
  vite:config   cacheDir: '/Users/rainkolwa/Personal/reproduce-vite-env/node_modules/.vite',
  vite:config   command: 'build',
  vite:config   mode: 'production',
  vite:config   isProduction: false,
  vite:config   preview: {
  vite:config     port: undefined,
  vite:config     strictPort: undefined,
  vite:config     host: undefined,
  vite:config     https: undefined,
  vite:config     open: true,
  vite:config     proxy: undefined,
  vite:config     cors: undefined
  vite:config   },
  vite:config   env: { BASE_URL: '/', MODE: 'production', DEV: true, PROD: false },
  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(0) { set: [Function (anonymous)] },
  vite:config   createResolver: [Function: createResolver],
  vite:config   optimizeDeps: {
  vite:config     esbuildOptions: { keepNames: undefined, preserveSymlinks: undefined }
  vite:config   }
  vite:config } +186ms
vite v2.7.9 building for production...
✓ 9 modules transformed.
dist/index.html                  0.38 KiB
dist/assets/index.b5862e96.js    1.17 KiB / gzip: 0.66 KiB
dist/assets/vendor.af2b58ca.js   49.45 KiB / gzip: 19.96 KiB

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn’t already an issue that reports the same bug to avoid creating a duplicate.
• Make sure this is a Vite issue and not a framework-specific issue. For example, if it’s a Vue SFC related bug, it should likely be reported to https://github.com/vuejs/vue-next instead.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.

[RainKolwa]

I think we also need this PR to make sure NODE_ENV is handled correctly.

[bluwy]

I think .env should have a lower priority, and should be fixed. It makes sense for scoped .env to overrides the unscoped env files.

EDIT: From the code, looks like it was intentional. I think we should document instead 🤔