"Failed to instantiate edge runtime.fig:load:flatten", "__dirname is not defined"

[cheapsteak]

Bug Report

Current behavior

Created a blank project to test middleware

Server starts up fine

> Success! Build completediming config:load:flatten Completed in 3ms
> Ready! Available at http://localhost:3000

but upon accessing localhost:3000, the page returns "This Edge Function has crashed", and the console logs

Failed to instantiate edge runtime.fig:load:flatten Completed in 3ms
__dirname is not defined

Expected behavior/code

The middleware function to run instead of returning page crash

Possible solution

Additional context/screenshots
Repro by running npm run ddev

Archive.zip

I don't believe this is a duplicate of #209 since I've tried running with node@16.19.0 and also downgrading to a version of vercel cli that was using edge-runtime@1.1.0 and received the same errors

[cheapsteak]

looks like I was missing the step of adding next as a dependency 🤦
(I thought I didn't need it since I thought I saw somewhere that middleware and edge functions were framwork agnostic)

apologies for the noise

[cheapsteak]

actually sorry this is now working locally with vercel dev but not working when deployed

function logs https://vercel.com/cheapsteak1/lskjdf/DTvY4XUMnwcJoGJU6vkq2rALiNcw/functions showing

[GET] /
13:56:48:09
ReferenceError: __dirname is not defined
    at worker.js:21:23819
    at worker.js:21:23861
    at worker.js:14:28
    at worker.js:21:24002
    at worker.js:14:28
    at worker.js:21:24667
    at worker.js:14:28
    at worker.js:21:25045
    at worker.js:14:28
    at worker.js:23:103

[GET] /favicon.ico
13:56:35:43
ReferenceError: __dirname is not defined
    at node_modules/next/dist/compiled/ua-parser-js/ua-parser.js:10:16756
    at node_modules/next/dist/compiled/ua-parser-js/ua-parser.js:10:16885
    at node_modules/next/dist/server/web/spec-extension/user-agent.js:8:41
    at node_modules/next/server.js:6:0
    at middleware.js:4:15
    at middleware:middleware.js:1:17

[Kikobeats]

Hello, the global __dirname is missing at Edge Runtime because it's a Node.js API and the Edge Runtime effort is to cover WinterCG API:

So it's expected to be missing there.

The thing is, if you do the same but using Next.js, __dirname exists:

That's because Next.js is extending Edge Runtime API surface, adding __dirname polyfill to be possible to cover more user cases.

[cheapsteak]

Thanks for clarifying 🙏 does that mean edge-runtime is only meant to be used with NextJS projects?

[Kikobeats]

Not really: You can extend Edge Runtime to add whatever you need:

const { EdgeRuntime } = require('edge-runtime')

const runtime = new EdgeRuntime({
  extend: context => {
    context.__dirname = __dirname
    return context
  }
})

Promise.resolve().then(async () => {
  const result = await runtime.evaluate('__dirname')
  console.log(result)
})

Take a look to https://edge-runtime.vercel.app/getting-started#usage 🙂