Setting "type": "module" in package.json in clean docusaurus project causes build to fail.

[rudfoss-rr]

I have a monorepo with multiple projects, one of which is a docusaurus documentation set. The monorepo uses pnpm workspaces so there is a package.json file at the the root and the documentation project (with its own package.json) is saved in ./docs.

At some point I flipped the root package.json "type" property to module and now docusaurus builds fail with an obscure error.

I tried to recreate the problem by creating a new, clean docusaurus project and it also fails when using "type": "module" so I curious if this is not supported or if there is a bug here.

I reproduced it on Windows 11 with pnpm v10.4.1 like this:

1. Create a new workspace using pnpm create docusaurus@latest docs-test classic
2. pnpm exec docusaurus build, works ✅
3. Add "type": "module" to package.json
4. pnpm exec docusaurus build, fails ❌

No changes to configuration and no changes to any files (except package.json). Is this a bug or is "type": "module" just not supported?

This is the raw output:

pnpm exec docusaurus build 
[INFO] [en] Creating an optimized production build...

√ Client
  Compiled successfully in 1.19s

√ Server
  


* Client █████████████████████████ cache (99%) shutdown IdleFileCachePlugin
 stored

√ Server
  


[ERROR] Error: Unable to build website for locale en.
    at tryToBuildLocale (C:\projects\docs-test\node_modules\.pnpm\@[email protected]_@doc_7fd4c8037771cc58e270c04c3c4530aa\node_modules\@docusaurus\core\lib\commands\build\build.js:78:15)  
    at async C:\projects\docs-test\node_modules\.pnpm\@[email protected]_@doc_7fd4c8037771cc58e270c04c3c4530aa\node_modules\@docusaurus\core\lib\commands\build\build.js:34:9
    at async mapAsyncSequential (C:\projects\docs-test\node_modules\.pnpm\@[email protected]_@sw_4cc57c5d3d2891b7e978ee1cd6e74368\node_modules\@docusaurus\utils\lib\jsUtils.js:21:24)      
    at async Command.build (C:\projects\docs-test\node_modules\.pnpm\@[email protected]_@doc_7fd4c8037771cc58e270c04c3c4530aa\node_modules\@docusaurus\core\lib\commands\build\build.js:33:5)
    at async Promise.all (index 0)
    at async runCLI (C:\projects\docs-test\node_modules\.pnpm\@[email protected]_@doc_7fd4c8037771cc58e270c04c3c4530aa\node_modules\@docusaurus\core\lib\commands\cli.js:56:5)
    at async file:///C:/projects/docs-test/node_modules/.pnpm/@[email protected]_@doc_7fd4c8037771cc58e270c04c3c4530aa/node_modules/@docusaurus/core/bin/docusaurus.mjs:44:3 {
  [cause]: TypeError: require.resolveWeak is not a function
      at 3562 (server.bundle.js:1963:443)
      at __webpack_require__ (server.bundle.js:21584:41)
      at 5562 (server.bundle.js:11100:77)
      at __webpack_require__ (server.bundle.js:21584:41)
      at 2127 (server.bundle.js:1093:86)
      at __webpack_require__ (server.bundle.js:21584:41)
      at 4618 (server.bundle.js:2468:75)
      at __webpack_require__ (server.bundle.js:21584:41)
      at 2906 (server.bundle.js:1518:66)
      at __webpack_require__ (server.bundle.js:21584:41)
}
[INFO] Docusaurus version: 3.8.1
Node version: v22.12.0

[Josh-Cena]

Please see #6520. Almost no part of your Docusaurus site (client-side or server-side) is designed to work with pure ESM; in particular, our webpack infra expects your client code to be in the "ambiguous" module mode.

[rudfoss-rr]

Understood, thanks for the quick reply!