🐛 BUG: cannot publish simple worker & horrible error message

[dotysan]

Which Cloudflare product(s) does this pertain to?

Wrangler

What version of Wrangler are you using?

2.16.0

What operating system are you using?

linux

Describe the Bug

This works:

import {Router} from 'itty-router';
const noContent = new Response(null, {status: 204});
const RTR= Router();
RTR
  .get('/', ()=> {return new Response('/')})
  .get('/favicon.ico', ()=> noContent)
  .all('*', ()=> new Response('404, not here!', {status: 404}))
;

But as soon as I try and define a 2nd Response() const...

import {Router} from 'itty-router';
const noContent = new Response(null, {status: 204});
const notHere = new Response('404, not here!', {status: 404});
const RTR= Router();
RTR
  .get('/', ()=> {return new Response('/')})
  .get('/favicon.ico', ()=> noContent)
  .all('*', ()=> notHere)
;

...then wrangler publish generates this horrible error message:

✘ [ERROR] A request to the Cloudflare API (/accounts/{account_identifier}/workers/scripts/{script_name}) failed.

  Uncaught Error: Some functionality, such as asynchronous I/O, timeouts, and generating random
  values, can only be performed while handling a request.
    at index.js:26:15
   [code: 10021]

It appears that simply defining two const foo = new Response() trips up the POST to the undocumented accounts/{account_identifier}/workers/scripts/{script_name}/edge-preview API.

The example above works perfectly if I do wrangler dev --local. (However wrangler dev also fails, why?)

Even if a) I'm doing something wrong, or b) it's actually a bug in itty-router, please fix the horrible error message! I can't even find where that index.js:26:15 lives.

[penalosa]

Thanks for reporting this! This is a limitation of the Cloudflare Workers runtime, where you can't create Response objects at the top level since it counts as performing I/O (which can only be performed inside the fetch event handler). We'll update the docs to make this clearer, but in the meantime if you modify your code to use arrow functions it should work:

import {Router} from 'itty-router';
const noContent = () => new Response(null, {status: 204});
const notHere = () => new Response('404, not here!', {status: 404});
const RTR= Router();
RTR
  .get('/', ()=> {return new Response('/')})
  .get('/favicon.ico', ()=> noContent())
  .all('*', ()=> notHere())
;

[dotysan]

Belated thanks, @penalosa!