Vite doesn't support ESM packages with "exports" field in SSR

[raythurnevoid]

Describe the bug

Because of this browserify/resolve#222 issue, Vite won't parse package.json "exports" field and will throw this error for packages that doesn't use "main" field:

3:03:07 AM [vite] Error when evaluating SSR module /src/components/context.ts:
Error [ERR_REQUIRE_ESM]: Must use import to load ES Module: C:\workspace\m7d\svelte-context-enhanced\website\node_modules\@raythurnevoid\svelte-context-enhanced\index.js
require() of ES modules is not supported.
require() of C:\workspace\m7d\svelte-context-enhanced\website\node_modules\@raythurnevoid\svelte-context-enhanced\index.js from C:\workspace\m7d\vite\packages\vite\dist\node\chunks\dep-4058344d.js is an ES module file as it is a .js file whose nearest parent package.json contains "type": "module" which defines all .js files in that package scope as ES modules.

I tried to replace resolve packages with webpack's enhanced-resolve: https://www.npmjs.com/package/enhanced-resolve
Their base code is extremely more hure and complicated than resolve but i've managed to make it work well in Vite: https://github.com/raythurnevoid/vite/commit/95a4f859fa31c4f052f2c3ab422b8f6e82154269

Another upside of enhanced-resolve is that it already supports also "imports" field, that could be a good replace for the numerous "alias" fields of tools like Jest, Rollup, Vite itself and tsconfig paths:
https://nodejs.org/api/packages.html#packages_imports
https://nodejs.org/api/packages.html#packages_subpath_imports

if this fix is feasible i'll open a PR with it.

Reproduction

To reproduce it's enough to import an ESM only package eg: https://github.com/raythurnevoid/strings-filter
Repo example: https://github.com/raythurnevoid/vite-esm-error-reproduction/tree/main

System Info

Output of npx envinfo --system --npmPackages vite,@vitejs/plugin-vue --binaries --browsers:

System:
    OS: Windows 10 10.0.19042
    CPU: (16) x64 AMD Ryzen 9 4900H with Radeon Graphics
    Memory: 16.09 GB / 31.42 GB
  Binaries:
    Node: 16.2.0 - C:\Program Files\nodejs\node.EXE
    Yarn: 1.22.10 - ~\AppData\Roaming\npm\yarn.CMD
    npm: 7.13.0 - C:\Program Files\nodejs\npm.CMD
  Browsers:
    Edge: Spartan (44.19041.1023.0), Chromium (91.0.864.54)
    Internet Explorer: 11.0.19041.1

Used package manager: npm

Logs

shows logs

PS C:\workspace\m7d\vite-esm> npm run dev

> test-ssr-vue@0.0.0 dev
> node server

http://localhost:3000
[@vue/compiler-sfc] <script setup> is still an experimental proposal.
Follow its status at https://github.com/vuejs/rfcs/pull/227.

[@vue/compiler-sfc] When using experimental features,
it is recommended to pin your vue dependencies to exact versions to avoid breakage.

7:35:45 PM [vite] Error when evaluating SSR module /src/pages/Home.vue:
Error [ERR_REQUIRE_ESM]: Must use import to load ES Module: C:\workspace\m7d\vite-esm\node_modules\@raythurnevoid\strings-filter\index.js
require() of ES modules is not supported.
require() of C:\workspace\m7d\vite-esm\node_modules\@raythurnevoid\strings-filter\index.js from C:\workspace\m7d\vite-esm\node_modules\vite\dist\node\chunks\dep-0ed4fbc0.js is an ES module file as it is a .js file whose nearest parent package.json contains 
"type": "module" which defines all .js files in that package scope as ES modules.
Instead rename index.js to end in .cjs, change the requiring code to use import(), or remove "type": "module" from C:\workspace\m7d\vite-esm\node_modules\@raythurnevoid\strings-filter\package.json.

    at new NodeError (node:internal/errors:363:5)
    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1126:13)
    at Module.load (node:internal/modules/cjs/loader:989:32)
    at Function.Module._load (node:internal/modules/cjs/loader:829:14)
    at Module.require (node:internal/modules/cjs/loader:1013:19)
    at require (node:internal/modules/cjs/helpers:93:18)
    at nodeRequire (C:\workspace\m7d\vite-esm\node_modules\vite\dist\node\chunks\dep-0ed4fbc0.js:69996:17)
    at ssrImport (C:\workspace\m7d\vite-esm\node_modules\vite\dist\node\chunks\dep-0ed4fbc0.js:69949:20)
    at eval (/src/pages/Home.vue:7:31)
    at instantiateModule (C:\workspace\m7d\vite-esm\node_modules\vite\dist\node\chunks\dep-0ed4fbc0.js:69982:166)
[Vue Router warn]: uncaught error during route navigation:
Error [ERR_REQUIRE_ESM]: Must use import to load ES Module: C:\workspace\m7d\vite-esm\node_modules\@raythurnevoid\strings-filter\index.js
require() of ES modules is not supported.
require() of C:\workspace\m7d\vite-esm\node_modules\@raythurnevoid\strings-filter\index.js from C:\workspace\m7d\vite-esm\node_modules\vite\dist\node\chunks\dep-0ed4fbc0.js is an ES module file as it is a .js file whose nearest parent package.json contains 
"type": "module" which defines all .js files in that package scope as ES modules.
Instead rename index.js to end in .cjs, change the requiring code to use import(), or remove "type": "module" from C:\workspace\m7d\vite-esm\node_modules\@raythurnevoid\strings-filter\package.json.

    at new NodeError (node:internal/errors:363:5)
    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1126:13)
    at Module.load (node:internal/modules/cjs/loader:989:32)
    at Function.Module._load (node:internal/modules/cjs/loader:829:14)
    at Module.require (node:internal/modules/cjs/loader:1013:19)
    at require (node:internal/modules/cjs/helpers:93:18)
    at nodeRequire (C:\workspace\m7d\vite-esm\node_modules\vite\dist\node\chunks\dep-0ed4fbc0.js:69996:17)
    at ssrImport (C:\workspace\m7d\vite-esm\node_modules\vite\dist\node\chunks\dep-0ed4fbc0.js:69949:20)
    at eval (/src/pages/Home.vue:7:31)
    at instantiateModule (C:\workspace\m7d\vite-esm\node_modules\vite\dist\node\chunks\dep-0ed4fbc0.js:69982:166) {
  code: 'ERR_REQUIRE_ESM'
}
Error [ERR_REQUIRE_ESM]: Must use import to load ES Module: C:\workspace\m7d\vite-esm\node_modules\@raythurnevoid\strings-filter\index.js
require() of ES modules is not supported.
require() of C:\workspace\m7d\vite-esm\node_modules\@raythurnevoid\strings-filter\index.js from C:\workspace\m7d\vite-esm\node_modules\vite\dist\node\chunks\dep-0ed4fbc0.js is an ES module file as it is a .js file whose nearest parent package.json contains 
"type": "module" which defines all .js files in that package scope as ES modules.
Instead rename index.js to end in .cjs, change the requiring code to use import(), or remove "type": "module" from C:\workspace\m7d\vite-esm\node_modules\@raythurnevoid\strings-filter\package.json.

    at new NodeError (node:internal/errors:363:5)
    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1126:13)
    at Module.load (node:internal/modules/cjs/loader:989:32)
    at Function.Module._load (node:internal/modules/cjs/loader:829:14)
    at Module.require (node:internal/modules/cjs/loader:1013:19)
    at require (node:internal/modules/cjs/helpers:93:18)
    at nodeRequire (C:\workspace\m7d\vite-esm\node_modules\vite\dist\node\chunks\dep-0ed4fbc0.js:69996:17)
    at ssrImport (C:\workspace\m7d\vite-esm\node_modules\vite\dist\node\chunks\dep-0ed4fbc0.js:69949:20)
    at eval (/src/pages/Home.vue:7:31)
    at instantiateModule (C:\workspace\m7d\vite-esm\node_modules\vite\dist\node\chunks\dep-0ed4fbc0.js:69982:166)
node:internal/process/promises:246
          triggerUncaughtException(err, true /* fromPromise */);
          ^

Error [ERR_REQUIRE_ESM]: Must use import to load ES Module: C:\workspace\m7d\vite-esm\node_modules\@raythurnevoid\strings-filter\index.js
require() of ES modules is not supported.
require() of C:\workspace\m7d\vite-esm\node_modules\@raythurnevoid\strings-filter\index.js from C:\workspace\m7d\vite-esm\node_modules\vite\dist\node\chunks\dep-0ed4fbc0.js is an ES module file as it is a .js file whose nearest parent package.json contains 
"type": "module" which defines all .js files in that package scope as ES modules.

    at new NodeError (node:internal/errors:363:5)
    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1126:13)
    at Module.load (node:internal/modules/cjs/loader:989:32)
    at Function.Module._load (node:internal/modules/cjs/loader:829:14)
    at Module.require (node:internal/modules/cjs/loader:1013:19)
    at require (node:internal/modules/cjs/helpers:93:18)
    at ssrImport (C:\workspace\m7d\vite-esm\node_modules\vite\dist\node\chunks\dep-0ed4fbc0.js:69949:20)
    at eval (/src/pages/Home.vue:7:31)
    at instantiateModule (C:\workspace\m7d\vite-esm\node_modules\vite\dist\node\chunks\dep-0ed4fbc0.js:69982:166) {
  code: 'ERR_REQUIRE_ESM'
}

---

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[aleclarson]

The error message seems to indicate that resolve is not the problem, but rather trying to require a module with ESM syntax. It seems that ESM-only modules need to be transformed before they're required (or use dynamic import instead).

vite/packages/vite/src/node/ssr/ssrExternal.ts

Lines 11 to 12 in 887c247

	* TODO right now externals are imported using require(), we probably need to
	* rework this when more libraries ship native ESM distributions for Node.

And from the docs:

In the future, this heuristics will likely improve to detect if the project has type: "module" enabled, so that Vite can also externalize dependencies that ship Node-compatible ESM builds by importing them via dynamic import() during SSR.

[benmccann]

Core SvelteKit functionality cannot be used because of this issue: sveltejs/kit#2237. The @sveltejs/kit package is an ESM package with an exports field and Vite doesn't know how to load it

[matthewp]

Snowpack resolved this issue by abstracting to use import() by default: https://github.com/snowpackjs/snowpack/blob/d8cc54a7816faef9d98459a1e24f54912163868b/snowpack/assets/require-or-import.js

[benmccann]

This is now causing problems for SvelteKit in a second way. Svelte exports different code on the client and server, but we always get the client-side version because resolve is broken: browserify/resolve#222.

[Niputi]

maybe this module could be of use for a implementation https://github.com/unjs/mlly

[benmccann]

https://www.npmjs.com/package/enhanced-resolve might be another alternative. It's used by webpack, so should be fairly battle-tested

[benmccann]

Here's a branch with enhanced-resolve: main...benmccann:enhanced-resolve

It's a pretty small change and seems to basically work. Some of the tests are failing though. I don't know that I'll have time to look into it, but thought I'd share in case it helps anyone who might want to give it a try

Edit: I didn't see, but it looks like there was also a proposal to make this change above. That version might work better, but I haven't tested yet: https://github.com/raythurnevoid/vite/commit/95a4f859fa31c4f052f2c3ab422b8f6e82154269

[benmccann]

I just tested @raythurnevoid's example from the issue description and it works now with Vite 2.7 except for one issue. The code looks like:

export * from "./classList";
export * from "./styleList";
export * from "./filterStrings";
export * from "./customList";
export * from "./types";

To get it to work I had to change it to:

export * from "./classList.js";
export * from "./styleList.js";
export * from "./filterStrings.js";
export * from "./customList.js";
export * from "./types.js";

I think that's working as intended though and is a bug in @raythurnevoid's example: https://stackoverflow.com/a/64242299

[benmccann]

This still doesn't work with https://github.com/Karlinator/reproduction-sveltekit-hooks when @sveltejs/kit is added to ssr/external

[benmccann]

It looks like @raythurnevoid and I had figured out different pieces of this. I combined our two solutions and sent a PR for it: #5593

[benmccann]

This would also be fixed by #3951

[frandiox]

@aleclarson Can we close this one? 🤔