From aebf72de902c86ae2379fe2bef60932a46b1e1a7 Mon Sep 17 00:00:00 2001
From: Tyreece Rozycki <57762380+KrystilizeNevaDies@users.noreply.github.com>
Date: Sun, 29 Jan 2023 22:05:28 +1000
Subject: [PATCH] Correctly send the player's main hand setting. (#1724)

* Update Player.java

* Use setNotifyAboutChanges and add integration test
---
 .../net/minestom/server/entity/Player.java    |  3 ++
 .../entity/player/PlayerIntegrationTest.java  | 32 +++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/src/main/java/net/minestom/server/entity/Player.java b/src/main/java/net/minestom/server/entity/Player.java
index 930c173ea..e7261e24e 100644
--- a/src/main/java/net/minestom/server/entity/Player.java
+++ b/src/main/java/net/minestom/server/entity/Player.java
@@ -2204,7 +2204,10 @@ public class Player extends LivingEntity implements CommandSender, Localizable,
             this.allowServerListings = allowServerListings;
 
             // TODO: Use the metadata object here
+            metadata.setNotifyAboutChanges(false);
             metadata.setIndex((byte) 17, Metadata.Byte(displayedSkinParts));
+            metadata.setIndex((byte) 18, Metadata.Byte((byte) (this.mainHand == MainHand.RIGHT ? 1 : 0)));
+            metadata.setNotifyAboutChanges(true);
         }
 
     }
diff --git a/src/test/java/net/minestom/server/entity/player/PlayerIntegrationTest.java b/src/test/java/net/minestom/server/entity/player/PlayerIntegrationTest.java
index 59ddf8a94..c9e3ddbe3 100644
--- a/src/test/java/net/minestom/server/entity/player/PlayerIntegrationTest.java
+++ b/src/test/java/net/minestom/server/entity/player/PlayerIntegrationTest.java
@@ -1,5 +1,7 @@
 package net.minestom.server.entity.player;
 
+import net.minestom.server.message.ChatMessageType;
+import net.minestom.server.network.packet.client.play.ClientSettingsPacket;
 import net.minestom.testing.Collector;
 import net.minestom.testing.Env;
 import net.minestom.testing.EnvTest;
@@ -45,6 +47,36 @@ public class PlayerIntegrationTest {
         assertAbilities(player, false, false, false, false);
     }
 
+    @Test
+    public void handSwapTest(Env env) {
+        ClientSettingsPacket packet = new ClientSettingsPacket("en_us", (byte) 16, ChatMessageType.FULL,
+                true, (byte) 127, Player.MainHand.LEFT, true, true);
+
+        var instance = env.createFlatInstance();
+        var connection = env.createConnection();
+        var player = connection.connect(instance, new Pos(0, 42, 0)).join();
+        assertEquals(instance, player.getInstance());
+        env.tick();
+        env.tick();
+
+        player.addPacketToQueue(packet);
+        var collector = connection.trackIncoming();
+        env.tick();
+        env.tick();
+        assertEquals(Player.MainHand.LEFT, player.getSettings().getMainHand());
+
+        boolean found = false;
+        for (ServerPacket serverPacket : collector.collect()) {
+            if (!(serverPacket instanceof EntityMetaDataPacket metaDataPacket)) {
+                continue;
+            }
+            assertEquals((byte) 0, metaDataPacket.entries().get(18).value(),
+                    "EntityMetaDataPacket has the incorrect hand after client settings update.");
+            found = true;
+        }
+        Assertions.assertTrue(found, "EntityMetaDataPacket not sent after client settings update.");
+    }
+
     private void assertAbilities(Player player, boolean isInvulnerable, boolean isFlying, boolean isAllowFlying,
                                  boolean isInstantBreak) {
         assertEquals(isInvulnerable, player.isInvulnerable());