Dynamic require of "path" is not supported

[jdion84]

im trying to build and run express server code

entry/server.js:

import express from 'express'

const app = express()

app.get('/', (req, res) => {
    res.send('Hello World!')
})

app.listen(3000, () => {
    console.log(`Example app listening on http://localhost:3000`)
})

entry/build.js:

import * as esbuild from 'esbuild'

await esbuild.build({
    entryPoints: [
        'entry/server.js',
    ],
    bundle: true,
    outdir: 'private',
    platform: 'node',
    format: 'esm',
})

package.json:

{
    "name": "bas-framework-2",
    "version": "1.0.0",
    "description": "",
    "main": "index.js",
    "scripts": {
        "test": "echo \"Error: no test specified\" && exit 1",
        "build": "node entry/build.js",
        "serve": "node private/server.js",
        "dev": "npm run build && npm run serve"
    },
    "keywords": [],
    "author": "",
    "license": "ISC",
    "type": "module",
    "devDependencies": {
        "esbuild": "^0.19.2",
        "express": "^4.18.2"
    }
}

when i do npm run dev i get this error:

file:///Users/jdion84/Sites/bas-framework-2/private/server.js:12
  throw Error('Dynamic require of "' + x + '" is not supported');
        ^

Error: Dynamic require of "path" is not supported
    at file:///Users/jdion84/Sites/bas-framework-2/private/server.js:12:9
    at node_modules/depd/index.js (file:///Users/jdion84/Sites/bas-framework-2/private/server.js:37:20)
    at __require2 (file:///Users/jdion84/Sites/bas-framework-2/private/server.js:15:50)
    at node_modules/body-parser/index.js (file:///Users/jdion84/Sites/bas-framework-2/private/server.js:16528:21)
    at __require2 (file:///Users/jdion84/Sites/bas-framework-2/private/server.js:15:50)
    at node_modules/express/lib/express.js (file:///Users/jdion84/Sites/bas-framework-2/private/server.js:21855:22)
    at __require2 (file:///Users/jdion84/Sites/bas-framework-2/private/server.js:15:50)
    at node_modules/express/index.js (file:///Users/jdion84/Sites/bas-framework-2/private/server.js:21924:22)
    at __require2 (file:///Users/jdion84/Sites/bas-framework-2/private/server.js:15:50)
    at file:///Users/jdion84/Sites/bas-framework-2/private/server.js:21929:30

Node.js v20.4.0

[hyrious]

This issue is already tracked here: https://github.com/evanw/esbuild/issues/1921

In summary, this runtime error is caused by bundling CJS libraries into ESM context (i.e. bundle express in format: 'esm'). esbuild uses closures to wrap these CJS liraries, and Node.js forbids dynamic (i.e. not at the top level) require on builtin modules.

I would still suggest you to exclude these dependencies from your bundle with --packages=external or --external:express since your runtime supports loading them from the file system, and it also bundles less code.

[ghost]

@hyrious will work if i deploy the code?

[ford-jones]

@hyrious will work if i deploy the code?

It depends on your deployment environment, if you are only sending the build output upstream then no - it won't. If you are sending the whole application root up, including any modules and all the other files needed to produce the build; then it should work fine :)