Expose setMaxListeners property on AbortSignal #54758

What is the problem this feature will solve?

Right now, there is no stable way to change the maxEventTargetListeners of an AbortSignal without importing from node:events.

This makes it impossible to write isomorphic library code that adds more than the default 10 event listeners, without having to resort to workarounds such as

/**
 * A workaround to set the `maxListeners` property of a node EventEmitter without having to import
 * the `node:events` module, which would make the code non-portable.
 */
function setMaxListeners(maxListeners: number, emitter: any) {
  const key = Object.getOwnPropertySymbols(new AbortController().signal).find(
    (key) => key.description === "events.maxEventTargetListeners"
  );
  if (key) emitter[key] = maxListeners;
}

This relies on the events.maxEventTargetListeners symbol description, which, to my knowledge is not part of any public API and could change at any time.

What is the feature you are proposing to solve the problem?

Add a AbortSignal.setMaxListeners instance method so isomorphic code could do something like

if ('setMaxListeners' in signal) signal.setMaxListeners(20)

What alternatives have you considered?

Alternatively, if this is not an option as it could pollute a spec-defined object with additional properties, use Symbol.for instead of new Symbol for kMaxEventTargetListeners and make that a part of the official api.

I would be willing to implement this feature.