fix(EventEmitter) only apply if listener #35577

[DerBasler]

Summary

During the rewrite of the event listeners in e5c5dcd a check was removed if the listener exists.
This change now checks that the listener is registred correctly.

Changelog

[INTERNAL] [FIXED] - make sure the event listener is registred correctly

Test Plan

Try to add an event listener without a proper func as parameter

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	8,494,057	-110,556
android	hermes	armeabi-v7a	7,814,976	-103,547
android	hermes	x86	8,975,632	-114,849
android	hermes	x86_64	8,829,633	-115,932
android	jsc	arm64-v8a	9,660,410	+486,577
android	jsc	armeabi-v7a	8,395,784	+30,291
android	jsc	x86	9,724,865	+493,377
android	jsc	x86_64	10,201,463	+711,282

Base commit: a6690bf
Branch: main

[javache]

Listeners should always be non-null. Could we consider fixing the calling packages instead?

[yungsters]

I agree with @javache.

This can only happen if addListener() is invoked with a non-function argument as its second argument. This happening seems like a symptom of an issue further upstream in the calling code.

If the point at which this becomes an error is too confusing to debug dependent packages, I'd be amenable to introducing a type check in addListener, for example:

if (typeof listener !== 'function') {
  throw new TypeError('EventEmitter.addListener(…): 2nd argument must be a function.');
}

[DerBasler]

Yes you guys are right I can adjust it over the weekend.
I guess I just wanted a quick fix for my problem 😅

[github-actions]

	Fails
🚫	📋 Missing Changelog - Please add a Changelog to your PR description. See Changelog format

	Warnings
⚠️	Libraries/vendor/emitter/tests/EventEmitter-test.js#L137 - Libraries/vendor/emitter/tests/EventEmitter-test.js line 137 – Unexpected alias 'result' for 'this'. (consistent-this)

Generated by 🚫 dangerJS against d307154

[yungsters]

I think I already landed this change in main. This PR can be closed now, right?

[DerBasler]

@yungsters ah I didn't notice nice 👍 thx for the info