From 24d9dbdc6b1528dad9794f9bf8956ac9c4e325c3 Mon Sep 17 00:00:00 2001
From: QiuHu <74653499+2982136527@users.noreply.github.com>
Date: Thu, 13 Aug 2026 20:23:58 +0800
Subject: [PATCH] fix(inventory): decode block-placement and swing hands via
 from_packet_id (#2876)

The placement and swing packet 'hand' fields use 0 = main hand, but they were
decoded with TryFrom<i32>, which maps 0 -> Hand::Left (that conversion is for
the client's dominant-hand setting). Hand::Left means off-hand in the inventory
API, so the decremented stack was written back to the off-hand instead of the
main hand, causing non-consumed placement and duplication into the off-hand.

Use Hand::from_packet_id for these packet fields and read the item via
inventory.get_stack_in_hand, matching the existing use_item handler.
---
 crates/pumpkin/src/net/java/play.rs | 20 ++++++--------------
 1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/crates/pumpkin/src/net/java/play.rs b/crates/pumpkin/src/net/java/play.rs
index f19c6cf10..e5beac5ea 100644
--- a/crates/pumpkin/src/net/java/play.rs
+++ b/crates/pumpkin/src/net/java/play.rs
@@ -1354,7 +1354,7 @@ impl JavaClient {
         swing_arm: SSwingArm,
     ) {
         player.update_last_action_time();
-        let Ok(hand) = Hand::try_from(swing_arm.hand.0) else {
+        let Ok(hand) = Hand::from_packet_id(swing_arm.hand.0) else {
             self.kick(TextComponent::text("Invalid hand")).await;
             return;
         };
@@ -2284,7 +2284,7 @@ impl JavaClient {
             return Err(BlockPlacingError::InvalidBlockFace);
         };
 
-        let Ok(hand) = Hand::try_from(use_item_on.hand.0) else {
+        let Ok(hand) = Hand::from_packet_id(use_item_on.hand.0) else {
             return Err(BlockPlacingError::InvalidHand);
         };
 
@@ -2299,11 +2299,8 @@ impl JavaClient {
         let held_item_empty = held_item.is_empty();
         let off_hand_item_empty = off_hand_item.is_empty();
 
-        let item_id = if matches!(hand, Hand::Left) {
-            held_item.item.id
-        } else {
-            off_hand_item.item.id
-        };
+        let mut item = inventory.get_stack_in_hand(hand).await;
+        let item_id = item.item.id;
         player
             .increment_stat(StatisticCategory::Used, item_id as i32, 1)
             .await;
@@ -2333,12 +2330,7 @@ impl JavaClient {
             }
         }}
 
-        let mut item = if matches!(hand, Hand::Left) {
-            held_item
-        } else {
-            off_hand_item
-        };
-        let equipment_slot = if matches!(hand, Hand::Left) {
+        let equipment_slot = if matches!(hand, Hand::Right) {
             EquipmentSlot::MAIN_HAND
         } else {
             EquipmentSlot::OFF_HAND
@@ -2371,7 +2363,7 @@ impl JavaClient {
             }
         }
 
-        let slot_index = if matches!(hand, Hand::Left) {
+        let slot_index = if matches!(hand, Hand::Right) {
             inventory.get_selected_slot() as usize
         } else {
             PlayerInventory::OFF_HAND_SLOT