`child_process.exec(...)` (and `fork`, `spawn`) do not abort with expected `signal.reason`

[MadLittleMods]

Version

v18.16.0

Platform

Microsoft Windows NT 10.0.19044.0 x64

Subsystem

No response

What steps will reproduce the bug?

1. Use Node.js v18.16.0
2. Run this script in the REPL or save as a script and run with Node.js

   (async () => {
    const { spawn } = require('child_process');
   
    const abortController = new AbortController();
    setTimeout(() => {
    abortController.abort(new Error('My custom error'));
    }, 0);
   
    try {
    await new Promise((resolve, reject) => {
    const child = spawn('echo', ["foo"], { signal: abortController.signal });
    child.on('error', (err) => {
    reject(err);
    });
    child.on('close', () => {
    resolve();
    });
    });
    } catch(err) {
    console.log('err', err);
    // err AbortError: The operation was aborted
    // at abortChildProcess (node:child_process:720:27)
    // at EventTarget.onAbortListener (node:child_process:790:7)
    // at [nodejs.internal.kHybridDispatch] (node:internal/event_target:737:20)
    // at EventTarget.dispatchEvent (node:internal/event_target:679:26)
    // at abortSignal (node:internal/abort_controller:314:10)
    // at AbortController.abort (node:internal/abort_controller:344:5)
    // at Timeout._onTimeout (REPL22:6:25)
    // at listOnTimeout (node:internal/timers:569:17)
    // at process.processTimers (node:internal/timers:512:7) {
    // code: 'ABORT_ERR'
    }
   })();

3. Notice AbortError: The operation was aborted instead of our custom signal.reason -> Error: My custom error

How often does it reproduce? Is there a required condition?

Consistently reproducible (always)

What is the expected behavior? Why is that the expected behavior?

I expect this to behave like the fetch API where the error thrown is the signal.reason that we aborted with. Example:

(async () => {
 const abortController = new AbortController();
 setTimeout(() => {
 abortController.abort(new Error('My custom error'));
 }, 0);

 try {
 const res = await fetch('https://nodejs.org/', { signal: abortController.signal });
 } catch(err) {
 console.log('err', err);
 // err Error: My custom error
 // at Object.fetch (node:internal/deps/undici/undici:11457:11)
 // at async REPL17:8:21
 }
})();

What do you see instead?

It always throws: AbortError: The operation was aborted

Additional information

Related to #43874

[benjamingr]

I expect this to behave like the fetch API where the error thrown is the signal.reason that we aborted with.

That's a bad API since signals get passed into things the code around it can't predict what exceptions may be thrown. The current behavior is intentional and what fetch does is really unfortunate.

[MadLittleMods]

AbortErrors shouldn't be overridable to reject with other stuff even if that's the .reason and should expose it as .cause instead. It means every user would need to refactor their error handling otherwise.

@benjamingr Your idea from #43874 to put the signal.reason as the Error: cause sounds decent. Whatever consistent thing would be nice.

It seems like things are converging on throwing signal.reason given fetch and #43874 🤷