import star works in dev but not in prod

[schontz]

Describe the bug

I am using an npm module that does not have TypeScript definitions. I imported it like so:

import * as rectClamp from 'rect-clamp' // ✅ dev ❌ prod

const clamped = rectClamp(...)

And it works fine in development. But when I build my code, I get a runtime error that the function is not defined. Changing the import like so works fine:

import rectClamp from 'rect-clamp' // ✅ dev ✅ prod

const clamped = rectClamp(...)

Reproduction

https://stackblitz.com/edit/vitejs-vite-kgbyd3?file=src%2Fmain.ts

Steps to reproduce

1. Visit the repro
2. In dev it prints Error: None
3. npm run build
4. Download the output and serve up dist locally
5. It prints out Error: TypeError: y is not a function

System Info

On StackBlitz:


  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: 8.14.0 - /usr/local/bin/pnpm
  npmPackages:
    vite: ^5.0.8 => 5.0.11 

### Used Package Manager

npm

### Logs

<details>
<summary>StackBlitz `vite build --debug`</summary>

```shell
  vite:config no config file found. +0ms
  vite:config using resolved config: {
  vite:config   root: '/home/projects/vitejs-vite-kgbyd3',
  vite:config   base: '/',
  vite:config   mode: 'production',
  vite:config   configFile: undefined,
  vite:config   logLevel: undefined,
  vite:config   clearScreen: undefined,
  vite:config   optimizeDeps: {
  vite:config     disabled: 'build',
  vite:config     force: undefined,
  vite:config     esbuildOptions: { preserveSymlinks: false }
  vite: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: true,
  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: false,
  vite:config     ssr: false,
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  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   configFileDependencies: [],
  vite:config   inlineConfig: {
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  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   rawBase: '/',
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  vite:config     conditions: [],
  vite:config     extensions: [
  vite:config       '.mjs',  '.js',
  vite:config       '.mts',  '.ts',
  vite:config       '.jsx',  '.tsx',
  vite:config       '.json'
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  vite:config     dedupe: [],
  vite:config     preserveSymlinks: false,
  vite:config     alias: [ [Object], [Object] ]
  vite:config   },
  vite:config   publicDir: '/home/projects/vitejs-vite-kgbyd3/public',
  vite:config   cacheDir: '/home/projects/vitejs-vite-kgbyd3/node_modules/.vite',
  vite:config   command: 'build',
  vite:config   ssr: {
  vite:config     target: 'node',
  vite:config     optimizeDeps: { disabled: true, esbuildOptions: [Object] }
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  vite:config   isWorker: false,
  vite:config   mainConfig: null,
  vite:config   isProduction: true,
  vite:config   plugins: [
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  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',
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  vite:config     'vite:terser',
  vite:config     'vite:reporter',
  vite:config     'vite:load-fallback'
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  vite:config   css: { lightningcss: undefined },
  vite:config   esbuild: { jsxDev: false },
  vite:config   server: {
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  vite:config     sourcemapIgnoreList: [Function: isInNodeModules$1],
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  vite:config     fs: {
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  vite:config     }
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  vite:config   preview: {
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  vite:config   assetsInclude: [Function: assetsInclude],
  vite:config   logger: {
  vite:config     hasWarned: false,
  vite:config     info: [Function: info],
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  vite:config     hasErrorLogged: [Function: hasErrorLogged]
  vite:config   },
  vite:config   packageCache: Map(1) {
  vite:config     'fnpd_/home/projects/vitejs-vite-kgbyd3' => {
  vite:config       dir: '/home/projects/vitejs-vite-kgbyd3',
  vite:config       data: [Object],
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  vite:config       webResolvedImports: {},
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  vite:config       setResolvedCache: [Function: setResolvedCache],
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  vite:config     },
  vite:config     set: [Function (anonymous)]
  vite:config   },
  vite:config   createResolver: [Function: createResolver],
  vite:config   worker: { format: 'iife', plugins: '() => plugins', rollupOptions: {} },
  vite:config   appType: 'spa',
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  vite:config   getSortedPlugins: [Function: getSortedPlugins],
  vite:config   getSortedPluginHooks: [Function: getSortedPluginHooks]
  vite:config } +5ms
vite v5.0.11 building for production...
src/main.ts (13:21) Cannot call a namespace ("rectClampBroken").
✓ 9 modules transformed.
dist/index.html                 0.46 kB │ gzip: 0.29 kB
dist/assets/index-s-MxoWxy.css  1.21 kB │ gzip: 0.63 kB
dist/assets/index-XVpmAzNt.js   4.01 kB │ gzip: 2.10 kB
✓ built in 284ms

Validations

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• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
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• The provided reproduction is a minimal reproducible example of the bug.

[bolt-new-by-stackblitz]

Start a new pull request in StackBlitz Codeflow.

• vitejs-vite-kgbyd3 (Open reproduction)

[XiSenao]

It seems that esbuild handles the behavior of module.exports = fn differently from rollup and it seems to be related to vite rewriting import * as.

[bluwy]

I think that

import * as rectClamp from 'rect-clamp' // ✅ dev ❌ prod

const clamped = rectClamp(...)

Should have not worked in dev. If you import star rectClamp should be an object, and executing as a function shouldn't work. I wonder if it's because Vite is misapplying the interop from esbuild.

[XiSenao]

I am confused why vite needs to perform the following operations during dev.

import * as rectClamp from 'rect-clamp' 

// rewrite 
import _rectClamp from 'rect-clamp';
const rectClamp = _rectClamp;

vite/packages/vite/src/node/plugins/importAnalysis.ts

Lines 1006 to 1009 in 2836276

	const lines: string[] = [`import ${cjsModuleName} from "${url}"`]
	importNames.forEach(({ importedName, localName }) => {
	if (importedName === '*') {
	lines.push(`const ${localName} = ${cjsModuleName}`)

Has this changed the meaning of the grammar?

[bluwy]

The code you linked which points to the function should have a brief description why. Basically for CJS packages, because you don't know the named exports in advanced, esbuild would bundle everything as module.exports = { named: ..., default ... }.

However, we still want import { named } from 'cjs-lib' to work, so we apply an "interop" here. I'm guessing the interop we're applying for namespace imports isn't correct.

Checking react-clamp, they're assigning the function to module.exports directly, so I guess that's unexpected in the handling code which would then incorrectly handle it.

[XiSenao]

what I mean to say is why don't we translate it as follows?

if (importedName === '*') {
  lines.push(`const ${localName} = {
    default: ${cjsModuleName}
  }`);
}

Instead of

if (importedName === '*') {
  lines.push(`const ${localName} = ${cjsModuleName}`);
}

When the properties are directly assigned to module.exports and use import *, rollup will only expose the default property value.

function _mergeNamespaces(n, m) {
    for (var i = 0; i < m.length; i++) {
        const e = m[i];
        if (typeof e !== 'string' && !Array.isArray(e)) { 
         // There is no iterable property in rectClamp
          for (const k in e) {
            if (k !== 'default' && !(k in n)) {
                const d = Object.getOwnPropertyDescriptor(e, k);
                if (d) {
                    Object.defineProperty(n, k, d.get ? d : {
                        enumerable: true,
                        get: () => e[k]
                    });
                }
            }
        } }
    }
    return Object.freeze(Object.defineProperty(n, Symbol.toStringTag, { value: 'Module' }));
}

function getDefaultExportFromCjs (x) {
	return x && x.__esModule && Object.prototype.hasOwnProperty.call(x, 'default') ? x['default'] : x;
}

_mergeNamespaces({
    __proto__: null,
    default: getDefaultExportFromCjs(rectClamp)
}, [rectClamp])

If the default behavior is not modified, I think vite may need to add a layer of compatibility in the build-import-analysis built-in plugin to synchronize with rollup's behavior.

[bluwy]

It's because the result of module.exports could be an object like { default: ... } and that can be assigned to the namespaced specifier directly. In this case, it's not an object but a function which trips Vite up.

I'm guessing the fix is to check if it has __esModule, and if true we can return the object directly, and if false we need to wrap with a { default: ... }? I'm not really sure yet the exact conditions when we should wrap it.

[XiSenao]

How about keeping in sync with rollup?

_mergeNamespaces({
    __proto__: null,
    default: getDefaultExportFromCjs(rectClamp)
}, [rectClamp])

or the behavior of Namespace Imports can be consistent with the handling of Dynamic Import, which I think it's not bad either. @bluwy

vite/packages/vite/src/node/plugins/importAnalysis.ts

Lines 870 to 876 in 9fc5d9c

	str.overwrite(
	expStart,
	expEnd,
	`import('${rewrittenUrl}').then(m => m.default && m.default.__esModule ? m.default : ({ ...m.default, default: m.default }))` +
	getLineBreaks(exp),
	{ contentOnly: true },
	)

Change the interactive logic of CJS to the following.

if (importedName === '*') {
  lines.push(`const ${localName} = ${cjsModuleName} && ${cjsModuleName}.__esModule ? ${cjsModuleName} : ({ ...${cjsModuleName}, default: ${cjsModuleName} })`)
}

[schontz]

Keeping in sync with what rollup does seems like the safest approach.

[XiSenao]

I am thinking about a question: why doesn't Vite leverage the ability of esbuild to transpile CommonJS into ESM during the build phase (perhaps it can also reuse pre-built artifacts)? Wouldn't this make it easier to smooth out inconsistencies in handling CommonJS artifacts between dev and build phases? 🤔