Is this fallback file:///_entry.js for import.meta.url normal ?

[qnp]

Environment

Node.js v18.20.4
Nitropack 2.11.4

Reproduction

1. npx giget@latest nitro nitro-app --install
2. cd nitro-app
3. Create server/plugins/test.ts and paste:

import path from 'path';
import fs from 'fs';
import { fileURLToPath } from 'url';

export const __filename = fileURLToPath(import.meta.url);
export const __dirname = path.dirname(__filename);

export default defineNitroPlugin(() => {
  const outDir = path.resolve(__dirname, '.test');
  console.log(outDir) // '/.test'
  if (!fs.existsSync(outDir)) fs.mkdirSync(outDir); // Error: EROFS: read-only file system, mkdir '/.test'
});

4. npm run build
5. node .output/server/index.mjs

Describe the bug

Hello, I am currently building locally a Nuxt project and then I run node --inspect .output/server/index.mjs in order to inspect the process. The server is build with Nitro. I have in the generated .output/server/chunks/runtime.mjs some reference to file system files using __dirname.

As we are in ES module, __dirname is deduced as:

import fs from 'fs';
import { fileURLToPath } from 'url';

const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);

But in the built bundle, import.meta is transformed by Rollup into globalThis._importMeta_ stub that ends up with url equal to "file:///_entry.js" according to this line of code in the Nitro plugin (isEntry is false for this file):

nitro/src/rollup/plugins/import-meta.ts

Line 20 in 14283fb

: '"file:///_entry.js"';

So __dirname is acutally / which is the root of my computer, not the root of the directory on which I run the process.

This is a problem because the process does not have rights to write into the root of the computer (please don't ask why I'm not root of my computer in my company), but anyway it should not write there.

I made a simple reproduction in Nitro JS directly.

If I edit the generated .output/server/chunks/runtime.mjs and replace stub url with import.meta.url, everything works as expected.

Additional context

No response

Logs

[pi0]

Yes this is intentional behavior. Since your code should remain portable, import.meta.url from source and dist is different and this is more a safeguard that you don't wrongly depend on it.

We might change this for Nitro v3 if there are usecases for it.

if you need to read assets, I would suggest to use useStorage instead.

[kingyue737]

I meet the same issue. I want to minify the server bundle and wrap them to a single file instead of using nitro's default bundling strategy:

 nitro: {
    minify: false,
    sourceMap: !isProd,
    noExternals: isProd,
    commonJS: {
      ignoreDynamicRequires: isProd,
    },
    rollupConfig: {
      plugins: [esmShim()],
      external: ['bufferutil', 'utf-8-validate'],
    },
  },

The esmShim plugin is used to inject the same shim as op for cjs packages:

import { fileURLToPath } from 'url';

const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);

But nitro replaces import.meta.url and causes the following error on Windows:

TypeError [ERR_INVALID_FILE_URL_PATH]: File URL path must be absolute
    at getPathFromURLWin32 (node:internal/url:1479:11)
    at Object.fileURLToPath (node:internal/url:1512:35)
    at file:///D:/Solutions/rho-meter/release/0.0.1/win-unpacked/resources/app.asar/.output/server/chunks/_/nitro.mjs:31:27
    at ModuleJob.run (node:internal/modules/esm/module_job:271:25)
    at async onImport.tracePromise.__proto__ (node:internal/modules/esm/loader:578:26)
    at async asyncRunEntryPointWithESMLoader (node:internal/modules/run_main:131:5) {
  code: 'ERR_INVALID_FILE_URL_PATH'

Maybe nitro v3 could provide a solution for such usecase

[pi0]

Nitro v3 doesn't has this shim anymore since most of runtimes have it natively now.

[qoo1476]

I encountered the same issue.

I'm using Prisma 6.12 with nuxt 4, and the generated client code includes something like:

import * as process from 'node:process'
import * as path from 'node:path'
import { fileURLToPath } from 'node:url'
const __dirname = path.dirname(fileURLToPath(import.meta.url))

Everything works fine in development mode,
but when I build and start the app, I get this error:

TypeError [ERR_INVALID_FILE_URL_PATH]: File URL path must be absolute

After some digging, I found that even though index.mjs defines this at the top:

import process from 'node:process'
globalThis._importMeta_ = { url: import.meta.url, env: process.env }

It doesn't get applied properly because nitro.mjs runs before index.mjs,
and it includes this code at the top:

import process from 'node:process'
globalThis._importMeta_ = globalThis._importMeta_ || { url: "file:///_entry.js", env: process.env }

As a result, the Prisma client ends up resolving __dirname using "file:///_entry.js", which causes the error.

My workaround was to use a polyfill:

scripts/polyfill.mjs

import process from 'node:process'
globalThis._importMeta_ = { url: import.meta.url, env: process.env }

And run with: node -r ./scripts/polyfill.mjs .output/server/index.mjs

I'm not sure if index.mjs is supposed to run first or if this is unintended behavior,
but at least this workaround fixes the issue for now.