Merge pull request #2161 from yogstation13/upstream-merge-39612

[MIRROR] Makes the signal redirect component a bit more transfer proof

code/datums/components/signal_redirect.dm

@@ -4,13 +4,20 @@
 /datum/component/redirect
 	dupe_mode = COMPONENT_DUPE_ALLOWED
 	var/list/signals
+	var/datum/callback/turfchangeCB
 
 /datum/component/redirect/Initialize(list/_signals, flags=NONE)
 	//It's not our job to verify the right signals are registered here, just do it.
 	if(!LAZYLEN(_signals))
 		return COMPONENT_INCOMPATIBLE
 	if(flags & REDIRECT_TRANSFER_WITH_TURF && isturf(parent))
-		RegisterSignal(parent, COMSIG_TURF_CHANGE, .proc/turf_change)
+		// If they also want to listen to the turf change then we need to set it up so both callbacks run
+		if(_signals[COMSIG_TURF_CHANGE])
+			turfchangeCB = _signals[COMSIG_TURF_CHANGE]
+			if(!istype(turfchangeCB))
+				. = COMPONENT_INCOMPATIBLE
+				CRASH("Redirect components must be given instanced callbacks, not proc paths.")
+		_signals[COMSIG_TURF_CHANGE] = CALLBACK(src, .proc/turf_change)
 	
 	signals = _signals
 
@@ -23,3 +30,4 @@
 
 /datum/component/redirect/proc/turf_change(path, new_baseturfs, flags, list/transfers)
 	transfers += src
+	return turfchangeCB?.InvokeAsync(arglist(args))