"Error: Request was cancelled" when using ProxyAgent

[NBNGaming]

Bug Description

When using ProxyAgent and http proxy responds with status code !== 200, Undici throws "Error: Request was cancelled". This error message is confusing and irrelevant to problem cause.
This line throws error:

undici/lib/proxy-agent.js

Line 103 in c415fbb

callback(new RequestAbortedError('Proxy response !== 200 when HTTP Tunneling'))

Expected Behavior

Throwing error with meaningful error "Proxy response !== 200 when HTTP Tunneling".

Logs & Screenshots

TypeError: fetch failed
    at fetch (node_modules/undici/index.js:109:13)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5) {
  cause: Error: Request was cancelled.
      at makeNetworkError (node_modules/undici/lib/fetch/response.js:351:9)
      at makeAppropriateNetworkError (node_modules/undici/lib/fetch/response.js:437:7)
      at httpNetworkFetch (node_modules/undici/lib/fetch/index.js:1763:14)
      at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
      at async httpNetworkOrCacheFetch (node_modules/undici/lib/fetch/index.js:1450:29)
      at async httpFetch (node_modules/undici/lib/fetch/index.js:1030:33)
      at async schemeFetch (node_modules/undici/lib/fetch/index.js:886:14)
      at async node_modules/undici/lib/fetch/index.js:599:16
      at async mainFetch (node_modules/undici/lib/fetch/index.js:583:16)
}

Environment

Ubuntu 22.04.2 and Windows 11
Node.js 18.16.0
Undici v5.22.1

[ronag]

PR welcome

[ronag]

The cause message should probably not be Request was cancelled. I'm not sure why the proper message isn't forwarded.

[NBNGaming]

Because this line replaces proper error with Request was cancelled

undici/lib/fetch/response.js

Line 437 in c415fbb

: makeNetworkError('Request was cancelled.')

[ronag]

Hm. Then I don't know what we can do without violating the spec. @KhafraDev

[KhafraDev]

a possible solution is to add an optional cause to makeNetworkError

[KhafraDev]

or we could forward the error message (haven't looked into if we can do it), it doesn't have to be Request was cancelled.. Not sure what part of that would violate the spec since it's only the error's cause?

[NBNGaming]

So, my pull request #2162 now can be merged?