IIFE Builds with Global Namespace Pollution When Using Optional Chaining and Class Fields

[iltimasd]

Describe the bug

I have project that is configured to build as an IIFE but is creating variables outside the actual IIFE.

This only happens if:

1. You are accessing a nested field within a global variable using optional chaining
   a. ie randomGlobal.randomFieldDepth1?.randomFieldDepth2
   b. optionally chaining root object works, randomGlobal?.randomFieldDepth1.randomFieldDepth2
2. Have a class that defines a field
   a. ie class bad { needsAFieldForSomeReason = 42; }
   b. removing the field works, class bad { }
   c. there might be other aspects to classes that trigger this, but this works for reproduction

Here is the config:

import { defineConfig } from 'vite';

export default defineConfig(() => {
  return {
    build: {
      lib: {
        name: 'THE_APP',
        entry: 'main.js',
        formats: ['iife'],
      },
    },
  };
});

Additionally I couldn't determine the correct options to replicate in esbuild, but here's an attempt, with all code encapsulated within the IIFE so might not be an esbuild problem(?).

In my specific case, the 2nd condition to repro is a given, the class is being declared deep in the dependency chain so I can't do anything about that. Where I'm introducing the bug is the 1st condition, optionally accessing a value from the window (a global). There is a workaround currently which is to just, ironically, use an IIFE to return the value. ie:

let optionalChaining = (()=>randomGlobal.random?.random2)();

It seems likely to be related to:
#11641 but this bug has the added caveat of the first condition.

Not sure if related to the following:
#14537
#14094

Excited to hear y'all's thoughts, thank you in advance.

Reproduction

https://stackblitz.com/edit/vitejs-vite-prc1zp?file=dist%2Fvite-starter.iife.js,main.js,index.html&terminal=dev

Steps to reproduce

1. Run npm run build
2. Observe that the js file in dist folder has declared vars outside the IIFE

System Info

From StackBlitz fyi

  System:
    OS: Linux 5.0 undefined
    CPU: (8) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Memory: 0 Bytes / 0 Bytes
    Shell: 1.0 - /bin/jsh
  Binaries:
    Node: 18.18.0 - /usr/local/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 9.4.2 - /usr/local/bin/npm
    pnpm: 8.9.2 - /usr/local/bin/pnpm
  npmPackages:
    vite: ^4.4.8 => 4.5.0

Used Package Manager

npm

Logs

Click to expand!

❯ npm install && npm run dev

added 8 packages in 590ms

3 packages are looking for funding
  run `npm fund` for details

> vite-starter@0.0.0 dev
> vite build -d && vite dev

  vite:config bundled config file loaded in 338.03ms +0ms
  vite:config using resolved config: {
  vite:config   build: {
  vite:config     target: [ 'es2020', 'edge88', 'firefox78', 'chrome87', 'safari14' ],
  vite:config     cssTarget: [ 'es2020', 'edge88', 'firefox78', 'chrome87', 'safari14' ],
  vite:config     outDir: 'dist',
  vite:config     assetsDir: 'assets',
  vite:config     assetsInlineLimit: 4096,
  vite:config     cssCodeSplit: false,
  vite:config     sourcemap: false,
  vite:config     rollupOptions: {},
  vite:config     minify: 'esbuild',
  vite:config     terserOptions: {},
  vite:config     write: true,
  vite:config     emptyOutDir: null,
  vite:config     copyPublicDir: true,
  vite:config     manifest: false,
  vite:config     lib: { name: 'THE_APP', entry: 'main.js', formats: [Array] },
  vite:config     ssr: false,
  vite:config     ssrManifest: false,
  vite:config     ssrEmitAssets: 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     modulePreload: { polyfill: true },
  vite:config     cssMinify: true
  vite:config   },
  vite:config   optimizeDeps: {
  vite:config     disabled: 'build',
  vite:config     force: undefined,
  vite:config     esbuildOptions: { preserveSymlinks: false }
  vite:config   },
  vite:config   configFile: '/home/projects/vitejs-vite-prc1zp/vite.config.js',
  vite:config   configFileDependencies: [ '/home/projects/vitejs-vite-prc1zp/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     optimizeDeps: { force: undefined },
  vite:config     build: {}
  vite:config   },
  vite:config   root: '/home/projects/vitejs-vite-prc1zp',
  vite:config   base: '/',
  vite:config   rawBase: '/',
  vite:config   resolve: {
  vite:config     mainFields: [ 'module', 'jsnext:main', 'jsnext' ],
  vite:config     browserField: true,
  vite:config     conditions: [],
  vite:config     extensions: [
  vite:config       '.mjs',  '.js',
  vite:config       '.mts',  '.ts',
  vite:config       '.jsx',  '.tsx',
  vite:config       '.json'
  vite:config     ],
  vite:config     dedupe: [],
  vite:config     preserveSymlinks: false,
  vite:config     alias: [ [Object], [Object] ]
  vite:config   },
  vite:config   publicDir: '/home/projects/vitejs-vite-prc1zp/public',
  vite:config   cacheDir: '/home/projects/vitejs-vite-prc1zp/node_modules/.vite',
  vite:config   command: 'build',
  vite:config   mode: 'production',
  vite:config   ssr: {
  vite:config     format: 'esm',
  vite:config     target: 'node',
  vite:config     optimizeDeps: { disabled: true, esbuildOptions: [Object] }
  vite:config   },
  vite:config   isWorker: false,
  vite:config   mainConfig: null,
  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: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:reporter',
  vite:config     'vite:load-fallback'
  vite:config   ],
  vite:config   css: undefined,
  vite:config   esbuild: { jsxDev: false },
  vite:config   server: {
  vite:config     preTransformRequests: true,
  vite:config     sourcemapIgnoreList: [Function: isInNodeModules],
  vite:config     middlewareMode: false,
  vite:config     fs: { strict: true, allow: [Array], deny: [Array] }
  vite:config   },
  vite:config   preview: {
  vite:config     port: undefined,
  vite:config     strictPort: undefined,
  vite:config     host: undefined,
  vite:config     https: undefined,
  vite:config     open: undefined,
  vite:config     proxy: undefined,
  vite:config     cors: undefined,
  vite:config     headers: undefined
  vite:config   },
  vite:config   envDir: '/home/projects/vitejs-vite-prc1zp',
  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-prc1zp' => {
  vite:config       dir: '/home/projects/vitejs-vite-prc1zp',
  vite:config       data: [Object],
  vite:config       hasSideEffects: [Function: hasSideEffects],
  vite:config       webResolvedImports: {},
  vite:config       nodeResolvedImports: {},
  vite:config       setResolvedCache: [Function: setResolvedCache],
  vite:config       getResolvedCache: [Function: getResolvedCache]
  vite:config     },
  vite:config     set: [Function (anonymous)]
  vite:config   },
  vite:config   createResolver: [Function: createResolver],
  vite:config   worker: {
  vite:config     format: 'iife',
  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:worker-post',
  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:load-fallback'
  vite:config     ],
  vite:config     rollupOptions: {},
  vite:config     getSortedPlugins: [Function: getSortedPlugins],
  vite:config     getSortedPluginHooks: [Function: getSortedPluginHooks]
  vite:config   },
  vite:config   appType: 'spa',
  vite:config   experimental: { importGlobRestoreExtension: false, hmrPartialAccept: false },
  vite:config   getSortedPlugins: [Function: getSortedPlugins],
  vite:config   getSortedPluginHooks: [Function: getSortedPluginHooks]
  vite:config } +6ms
vite v4.5.0 building for production...
  vite:esbuild 15.32ms tsconfck init /home/projects/vitejs-vite-prc1zp +0ms
✓ 1 modules transformed.
dist/vite-starter.iife.js  0.42 kB │ gzip: 0.30 kB
✓ built in 103ms```
</details>

### Validations

- [X] Follow our [Code of Conduct](https://github.com/vitejs/vite/blob/main/CODE_OF_CONDUCT.md)
- [X] Read the [Contributing Guidelines](https://github.com/vitejs/vite/blob/main/CONTRIBUTING.md).
- [X] Read the [docs](https://vitejs.dev/guide).
- [X] Check that there isn't [already an issue](https://github.com/vitejs/vite/issues) that reports the same bug to avoid creating a duplicate.
- [X] 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 [vuejs/core](https://github.com/vuejs/core) instead.
- [X] Check that this is a concrete bug. For Q&A open a [GitHub Discussion](https://github.com/vitejs/vite/discussions) or join our [Discord Chat Server](https://chat.vitejs.dev/).
- [X] The provided reproduction is a [minimal reproducible example](https://stackoverflow.com/help/minimal-reproducible-example) of the bug.

[stackblitz]

Start a new pull request in StackBlitz Codeflow.

• vitejs-vite-prc1zp (Open reproduction)

[iltimasd]

I should add, I have other apps that meet the above repro requirements, but dont exhibit the bug. much easier to prune to find a bug, then find out why a bug isnt happening

[sapphi-red]

There was a bug in esbuild (evanw/esbuild#3322). The fix landed in 0.19.x but Vite 4.4.x/4.5.x uses esbulid 0.18.x, so we cannot backport the fix.

Closing as this is fixed in Vite 5.

related: #14065