From 601f6faea523d3106cbac86ea6ef7c2bf15e5031 Mon Sep 17 00:00:00 2001
From: MrMelbert <51863163+MrMelbert@users.noreply.github.com>
Date: Sun, 5 Oct 2025 17:24:35 -0500
Subject: [PATCH] Chainsaw nullrod fix (#93283)

## About The Pull Request

Fixes #93280

It would give you the null rod arm, then equip the null rod, then try to
give you the null rod arm again, which removed your null rod arm and
caused... problems

## Changelog

:cl: Melbert
fix: Fixed chainsaw nullrod
/:cl:
---
 code/datums/components/prosthetic_item.dm     |  3 +++
 .../job_types/chaplain/chaplain_nullrod.dm    |  3 ++-
 code/modules/unit_tests/surgeries.dm          | 22 +++++++++++++++++++
 3 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/code/datums/components/prosthetic_item.dm b/code/datums/components/prosthetic_item.dm
index b8876f5484f..1537535974f 100644
--- a/code/datums/components/prosthetic_item.dm
+++ b/code/datums/components/prosthetic_item.dm
@@ -137,6 +137,9 @@
  * Returns the created pseudopart
  */
 /mob/living/carbon/proc/make_item_prosthetic(obj/item/some_thing, target_zone = BODY_ZONE_R_ARM, fall_prob = 0)
+	if(HAS_TRAIT_FROM(some_thing, TRAIT_NODROP, HAND_REPLACEMENT_TRAIT))
+		CRASH("make_item_prosthetic given an item that is already a prosthetic limb!")
+
 	var/obj/item/bodypart/existing = get_bodypart(target_zone)
 	existing?.drop_limb(special = TRUE)
 
diff --git a/code/modules/jobs/job_types/chaplain/chaplain_nullrod.dm b/code/modules/jobs/job_types/chaplain/chaplain_nullrod.dm
index de65b4e7021..96587e0159e 100644
--- a/code/modules/jobs/job_types/chaplain/chaplain_nullrod.dm
+++ b/code/modules/jobs/job_types/chaplain/chaplain_nullrod.dm
@@ -459,13 +459,14 @@
 /obj/item/nullrod/chainsaw/on_selected(obj/item/nullrod/old_weapon, mob/living/picker)
 	if(!iscarbon(picker))
 		return
+	to_chat(picker, span_warning("[src] takes the place of your arm!"))
 	var/obj/item/bodypart/active = picker.get_active_hand()
 	var/mob/living/carbon/new_hero = picker
 	new_hero.make_item_prosthetic(src, active.body_zone)
 
 /obj/item/nullrod/chainsaw/equipped(mob/living/carbon/user, slot, initial)
 	. = ..()
-	if(!iscarbon(user))
+	if(!iscarbon(user) || HAS_TRAIT_FROM(src, TRAIT_NODROP, HAND_REPLACEMENT_TRAIT))
 		return
 	if(!(slot & ITEM_SLOT_HANDS))
 		return
diff --git a/code/modules/unit_tests/surgeries.dm b/code/modules/unit_tests/surgeries.dm
index 8d2901bf77f..726e9808679 100644
--- a/code/modules/unit_tests/surgeries.dm
+++ b/code/modules/unit_tests/surgeries.dm
@@ -131,3 +131,25 @@
 	basic_brute_heal.success(user, clothed_patient, BODY_ZONE_CHEST)
 
 	TEST_ASSERT(naked_patient.getBruteLoss() < clothed_patient.getBruteLoss(), "Naked patient did not heal more from wounds tending than a clothed patient")
+
+/// Tests items-as-prosthetic-limbs can apply
+/datum/unit_test/prosthetic_item
+
+/datum/unit_test/prosthetic_item/Run()
+	var/mob/living/carbon/human/patient = allocate(/mob/living/carbon/human/consistent)
+	var/obj/item/claymore/sword = allocate(/obj/item/claymore)
+
+	patient.make_item_prosthetic(sword)
+
+	TEST_ASSERT(HAS_TRAIT_FROM(sword, TRAIT_NODROP, HAND_REPLACEMENT_TRAIT), "Prosthetic item attachment failed! Item does not have the nodrop trait")
+
+/// Specifically checks the chainsaw nullrod
+/datum/unit_test/prosthetic_item/nullrod
+
+/datum/unit_test/prosthetic_item/nullrod/Run()
+	var/mob/living/carbon/human/picker = allocate(/mob/living/carbon/human/consistent)
+	var/obj/item/nullrod/chainsaw/nullrod = allocate(/obj/item/nullrod/chainsaw)
+
+	nullrod.on_selected(null, picker)
+
+	TEST_ASSERT(HAS_TRAIT_FROM(nullrod, TRAIT_NODROP, HAND_REPLACEMENT_TRAIT), "Chainsaw nullrod item attachment failed! Item does not have the nodrop trait")