I have a Rails 7 app with esbuild :

esbuild.config.js :

#!/usr/bin/env node

const watch              = process.argv.includes("--watch");
const esbuild            = require('esbuild')
const coffeeScriptPlugin = require('esbuild-coffeescript');
const esbuildSvelte      = require('esbuild-svelte');
const sveltePreprocess   = require('svelte-preprocess');

esbuild
  .build({
    entryPoints: ["app/javascript/all.js"],
    bundle: true,
    outfile: "app/assets/builds/all.js",
    // outdir: "app/assets/builds/",
    plugins: [
      esbuildSvelte({
        preprocess: sveltePreprocess({coffeescript: { bare: true }}),
      }),
      // coffeeScriptPlugin({bare: true}), I TRIED THIS TOO...
    ],
    logLevel: "debug",
    watch: watch
  })
  .catch(() => process.exit(1));

my.svelte :

<script lang="coffee">
  test = ->
    console.log 'test coffee'

  test()
</script>

got an error :

node ./esbuild.config.js --watch
04:08:17 js.1 | ✘ [ERROR] [plugin esbuild-svelte] missing </

package.json :

{
  "name": "app",
  "private": "true",
  "dependencies": {
    "@hotwired/stimulus": "^3.0.1",
    "@hotwired/turbo-rails": "^7.1.3",
    "esbuild": "^0.14.43",
    "esbuild-coffeescript": "^2.0.0",
    "esbuild-svelte": "^0.7.1",
    "sass": "^1.52.3",
    "svelte": "^3.48.0",
    "svelte-preprocess": "^4.10.7"
  },
  "scripts": {
    "build": "node ./esbuild.config.js"
  }
}

How add coffeescript in svelte with Rails ?