From 2c74bb39e9edd837fc951724723bc9ec1983690e Mon Sep 17 00:00:00 2001
From: magatsuchi <88991542+magatsuchi@users.noreply.github.com>
Date: Tue, 26 Apr 2022 00:00:47 -0500
Subject: [PATCH] fixes unintended merge behavior (#66495)

---
 code/game/objects/items/stacks/stack.dm  |  9 ++++++---
 code/modules/unit_tests/outfit_sanity.dm | 11 +++++++++++
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/code/game/objects/items/stacks/stack.dm b/code/game/objects/items/stacks/stack.dm
index be1eb870bb4..6efe730f822 100644
--- a/code/game/objects/items/stacks/stack.dm
+++ b/code/game/objects/items/stacks/stack.dm
@@ -440,14 +440,17 @@
  *
  * Arguments:
  * - [check][/obj/item/stack]: The stack to check for mergeability.
+ * - [inhand][boolean]: Whether or not the stack to check should act like it's in a mob's hand.
  */
-/obj/item/stack/proc/can_merge(obj/item/stack/check)
+/obj/item/stack/proc/can_merge(obj/item/stack/check, inhand = FALSE)
 	if(!istype(check, merge_type))
 		return FALSE
 	if(mats_per_unit ~! check.mats_per_unit) // ~! in case of lists this operator checks only keys, but not values
 		return FALSE
 	if(is_cyborg) // No merging cyborg stacks into other stacks
 		return FALSE
+	if(ismob(loc) && !inhand) // no merging with items that are on the mob
+		return FALSE
 	return TRUE
 
 /**
@@ -505,7 +508,7 @@
 		INVOKE_ASYNC(src, .proc/merge, arrived)
 
 /obj/item/stack/hitby(atom/movable/hitting, skipcatch, hitpush, blocked, datum/thrownthing/throwingdatum)
-	if(can_merge(hitting))
+	if(can_merge(hitting, inhand = TRUE))
 		merge(hitting)
 	. = ..()
 
@@ -556,7 +559,7 @@
 	is_zero_amount(delete_if_zero = TRUE)
 
 /obj/item/stack/attackby(obj/item/W, mob/user, params)
-	if(can_merge(W))
+	if(can_merge(W, inhand = TRUE))
 		var/obj/item/stack/S = W
 		if(merge(S))
 			to_chat(user, span_notice("Your [S.name] stack now contains [S.get_amount()] [S.singular_name]\s."))
diff --git a/code/modules/unit_tests/outfit_sanity.dm b/code/modules/unit_tests/outfit_sanity.dm
index 1877d946c83..bfecf5e059c 100644
--- a/code/modules/unit_tests/outfit_sanity.dm
+++ b/code/modules/unit_tests/outfit_sanity.dm
@@ -8,6 +8,17 @@
 	outfit_item.on_outfit_equip(H, FALSE, ##slot_name); \
 }
 
+/// See #66313 and #60901. outfit_sanity used to runtime whenever you had two mergable sheets in either hand. Previously, this only had a 3% chance of occuring. Now 100%.
+/datum/outfit/stacks_in_hands
+	name = "Mr. Runtime"
+
+	uniform = /obj/item/clothing/under/suit/tuxedo
+	glasses = /obj/item/clothing/glasses/sunglasses
+	mask = /obj/item/clothing/mask/cigarette/cigar/havana
+	shoes = /obj/item/clothing/shoes/laceup
+	l_hand = /obj/item/stack/spacecash/c1000
+	r_hand = /obj/item/stack/spacecash/c1000
+
 /datum/unit_test/outfit_sanity/Run()
 	var/mob/living/carbon/human/H = allocate(/mob/living/carbon/human)