Getting to the bottom of: mix tailwind exited with 1 in Phoenix

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I've been playing with Phoenix lately and it's been a bit of adjustment coming from Next.js, Django and Rails. Most issues I've come up agains have been entirely user error, I read some more and figure out the issue was me all along. One issue I ran into recently however, was when adding Tailwind to a new Phoenix project.

What happened?

I went through the instructions to add Tailwind without dealign with nom and node. But I kept running into the same issue.

mix tailwind --runtime-config default
Generated tailwind_test app
const internalModuleReadJSON = function (f) { return require('fs').internalModuleReadJSON(f); };

TypeError: require(...).internalModuleReadJSON is not a function
    at internalModuleReadJSON (node:internal/modules/package_json_reader:4:68)
    at (node:internal/modules/package_json_reader:21:42)
    at readPackage (node:internal/modules/cjs/loader:296:36)
    at readPackageScope (node:internal/modules/cjs/loader:329:19)
    at trySelf (node:internal/modules/cjs/loader:444:40)
    at Function.Module._resolveFilename (node:internal/modules/cjs/loader:910:24)
    at Function.Module._load (node:internal/modules/cjs/loader:778:27)
    at Module.require (node:internal/modules/cjs/loader:1005:19)
    at Module._preloadModules (node:internal/modules/cjs/loader:1276:12)
    at loadPreloadModules (node:internal/bootstrap/pre_execution:487:5)
** (Mix) `mix tailwind default` exited with 1

Where is the issue?

After a trying different versions of the mix library, then the tailwind-cli directly, I finally found the problem.

An issue on the vercel/pkg repo reveals the problem, Packaged apps crash with zero messaging when NODE_OPTIONS is set

I usually run my projects in the VS Code terminal, what I didn't realise is that the NODE_OPTIONS environment variable is set to make debugging easier and this causes issues with the tailwind-cli.

Why does it happen?

The reason this happens is due to the tool, vercel/pkg. It's a tool for packaging a node app into a single binary and Tailwind uses this to create their CLI. The benefit to users is that if you don't want to deal with Node and NPM directly, you can use tailwind-cli without any dependencies.

How did I work around this?

Run it from another terminal

The VS Code terminal is convenient but with this issue, the easiest workaround is to run the commands in a standalone terminal of your choice.

Unset the environment variable

Running unset NODE_OPTIONS in the VS Code integrated terminal before mix tailwind default worked for me and lasts for the session.

VS Code settings

I also had success adding the following to the workspace settings - .vscode/settings.json

  "debug.javascript.terminalOptions": {
    "env": null

This will disable the ability to attach to code in the project automatically but for a Phoenix project where I was avoiding using Node anyway, this isn't a problem.

There you have it. Hopefully this issue will be resolved in future and this workaround won't be needed but as of Tailwind 3.0.24, it's useful to know when running from a VS Code integrated terminal. I used mix tailwind --runtime-config default mainly for testing my tailwind setup, if you're using this with phoenix you'll likely be running mix phx.server.

Seth Corker

A Fullstack Software Engineer working with React and Django. My main focus is JavaScript specialising in frontend UI with React. I like to explore different frameworks and technologies in my spare time. Learning languages (programming and real life) is a blast.