Error: Cannot find module 'chokidar'

[covariantcorp]

Describe the bug
From matlab-ls::stderr in emacs

node:internal/modules/cjs/loader:1451
throw err;
^

Error: Cannot find module 'chokidar'
Require stack:

• /usr/local/apps/matlabls/out/index.js
  at Module._resolveFilename (node:internal/modules/cjs/loader:1448:15)
  at defaultResolveImpl (node:internal/modules/cjs/loader:1059:19)
  at resolveForCJSWithHooks (node:internal/modules/cjs/loader:1064:22)
  at Module._load (node:internal/modules/cjs/loader:1234:25)
  at TracingChannel.traceSync (node:diagnostics_channel:328:14)
  at wrapModuleLoad (node:internal/modules/cjs/loader:245:24)
  at Module.require (node:internal/modules/cjs/loader:1548:12)
  at require (node:internal/modules/helpers:152:16)
  at Object.chokidar (/usr/local/apps/matlabls/out/index.js:65415:18)
  at webpack_require (/usr/local/apps/matlabls/out/index.js:70880:42) {
  code: 'MODULE_NOT_FOUND',
  requireStack: [ '/usr/local/apps/matlabls/out/index.js' ]
  }

Node.js v24.13.1

Process matlab-ls stderr finished

To Reproduce
Steps to reproduce the behavior:
load a .m file

Expected behavior
A clear and concise description of what you expected to happen.

Screenshots
If applicable, add screenshots to help explain your problem.

Useful Information

• MATLAB Version: R2025B
• OS Version: Ubuntu 24.04.4 LTS
• Language Server Client: emacs
• Client Version: 30.2

Additional context
Add any other context about the problem here.

[dklilley]

Hi @covariantcorp, thanks for reaching out about this!

I haven't run into this myself, but perhaps this is an OS-dependent issue. I suspect this is due to line 21 within webpack.config.js:

externals: ["chokidar"],

I presume you are building the language server locally? If so, can you try removing this line, then rebuild and see if the issue is resolved?

[covariantcorp]

I tried removing that line and I still get the error:

node:internal/modules/cjs/loader:1451
throw err;
^

Error: Cannot find module 'chokidar'
Require stack:

• /usr/local/apps/matlabls/out/index.js
  at Module._resolveFilename (node:internal/modules/cjs/loader:1448:15)
  at defaultResolveImpl (node:internal/modules/cjs/loader:1059:19)
  at resolveForCJSWithHooks (node:internal/modules/cjs/loader:1064:22)
  at Module._load (node:internal/modules/cjs/loader:1234:25)
  at TracingChannel.traceSync (node:diagnostics_channel:328:14)
  at wrapModuleLoad (node:internal/modules/cjs/loader:245:24)
  at Module.require (node:internal/modules/cjs/loader:1548:12)
  at require (node:internal/modules/helpers:152:16)
  at Object.chokidar (/usr/local/apps/matlabls/out/index.js:65415:18)
  at webpack_require (/usr/local/apps/matlabls/out/index.js:70880:42) {
  code: 'MODULE_NOT_FOUND',
  requireStack: [ '/usr/local/apps/matlabls/out/index.js' ]
  }

Node.js v24.13.1

Process matlab-ls stderr finished

[dklilley]

Thanks for giving that a try!

I will need to try this out on my end, on a Linux machine, and see if I can reproduce the error.

[dklilley]

I have not been able to reproduce this with VS Code on either Windows or Linux. This is perhaps because, within VS Code, the language server has access to VS Code's node modules.

My best guess at this point is that this is somehow related to chokidar being listed as an external library, but I'm not sure why simply removing that line from the webpack.config.js file and rebuilding didn't resolve the error.

As a workaround for now, I believe this should be resolved if you install chokidar locally on your system:

npm install -g chokidar

This should enable the language server to find and use the dependency.

[covariantcorp]

That didn't work either. I have installed chokidar. Does this look correct?

npm list chokidar
matlab-language-server@1.3.8 /home/chris/temp/MATLAB-language-server-1.3.8
├── chokidar@3.6.0
└─┬ mocha@10.7.3
└── chokidar@3.6.0 deduped

but I still get this error in Emacs:
node:internal/modules/cjs/loader:1451
throw err;
^

Error: Cannot find module 'chokidar'
Require stack:

• /usr/local/apps/matlabls/out/index.js
  at Module._resolveFilename (node:internal/modules/cjs/loader:1448:15)
  at defaultResolveImpl (node:internal/modules/cjs/loader:1059:19)
  at resolveForCJSWithHooks (node:internal/modules/cjs/loader:1064:22)
  at Module._load (node:internal/modules/cjs/loader:1234:25)
  at TracingChannel.traceSync (node:diagnostics_channel:328:14)
  at wrapModuleLoad (node:internal/modules/cjs/loader:245:24)
  at Module.require (node:internal/modules/cjs/loader:1548:12)
  at require (node:internal/modules/helpers:152:16)
  at Object.chokidar (/usr/local/apps/matlabls/out/index.js:65415:18)
  at webpack_require (/usr/local/apps/matlabls/out/index.js:70880:42) {
  code: 'MODULE_NOT_FOUND',
  requireStack: [ '/usr/local/apps/matlabls/out/index.js' ]
  }

Node.js v24.13.1

Process matlab-ls stderr finished

[dklilley]

This is what I see as well, so this error is quite puzzling.

Just to check - are you using these instructions for setting up the MATLAB language server within Emacs?

[covariantcorp]

Yes - I was following those instructions.