Handle items with invalid amount in 1.20.3->.5 (#3889)

api/src/main/java/com/viaversion/viaversion/api/configuration/ViaVersionConfig.java

@@ -457,4 +457,11 @@ public interface ViaVersionConfig extends Config {
      * @return the value sent to 1.19+ clients on join
      */
     boolean enforceSecureChat();
+
+    /**
+     * Handles items with invalid count values (higher than max stack size) on 1.20.3 servers.
+     *
+     * @return true if enabled
+     */
+    boolean handleInvalidItemCount();
 }

common/src/main/java/com/viaversion/viaversion/configuration/AbstractViaConfig.java

@@ -90,6 +90,7 @@ public abstract class AbstractViaConfig extends Config implements ViaVersionConf
     private boolean cache1_17Light;
     private boolean translateOcelotToCat;
     private boolean enforceSecureChat;
+    private boolean handleInvalidItemCount;
 
     protected AbstractViaConfig(final File configFile, final Logger logger) {
         super(configFile, logger);
@@ -159,6 +160,7 @@ public abstract class AbstractViaConfig extends Config implements ViaVersionConf
         cache1_17Light = getBoolean("cache-1_17-light", true);
         translateOcelotToCat = getBoolean("translate-ocelot-to-cat", true);
         enforceSecureChat = getBoolean("enforce-secure-chat", false);
+        handleInvalidItemCount = getBoolean("handle-invalid-item-count", false);
     }
 
     private BlockedProtocolVersions loadBlockedProtocolVersions() {
@@ -535,4 +537,9 @@ public abstract class AbstractViaConfig extends Config implements ViaVersionConf
     public boolean enforceSecureChat() {
         return enforceSecureChat;
     }
+
+    @Override
+    public boolean handleInvalidItemCount() {
+        return handleInvalidItemCount;
+    }
 }

common/src/main/java/com/viaversion/viaversion/protocols/v1_20_3to1_20_5/data/MaxStackSize1_20_3.java

@@ -0,0 +1,79 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2024 ViaVersion and contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package com.viaversion.viaversion.protocols.v1_20_3to1_20_5.data;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public final class MaxStackSize1_20_3 {
+
+    private static final Map<Integer, Integer> mapping = new HashMap<>();
+
+    static {
+        fill(521, 537, 1);
+        fill(764, 790, 1);
+        mapping.put(793, 1);
+        mapping.put(795, 1);
+        mapping.put(797, 1);
+        fill(814, 843, 1);
+        mapping.put(846, 1);
+        mapping.put(853, 1);
+        fill(854, 876, 1);
+        fill(883, 905, 16);
+        fill(906, 908, 1);
+        mapping.put(909, 16);
+        fill(911, 917, 1);
+        mapping.put(924, 16);
+        mapping.put(927, 1);
+        mapping.put(928, 1);
+        mapping.put(930, 1);
+        fill(960, 976, 1);
+        mapping.put(980, 1);
+        mapping.put(990, 16);
+        mapping.put(995, 1);
+        mapping.put(1085, 1);
+        mapping.put(1086, 16);
+        mapping.put(1107, 1);
+        mapping.put(1113, 1);
+        mapping.put(1116, 16);
+        fill(1117, 1120, 1);
+        mapping.put(1123, 1);
+        fill(1126, 1141, 16);
+        mapping.put(1149, 1);
+        mapping.put(1151, 1);
+        fill(1154, 1156, 1);
+        fill(1159, 1176, 1);
+        mapping.put(1178, 1);
+        mapping.put(1182, 1);
+        mapping.put(1183, 1);
+        fill(1185, 1191, 1);
+        mapping.put(1212, 16);
+        mapping.put(1256, 1);
+    }
+
+    public static int getMaxStackSize(final int identifier) {
+        return mapping.getOrDefault(identifier, 64);
+    }
+
+    private static void fill(final int start, final int end, final int value) {
+        for (int i = start; i <= end; i++) {
+            mapping.put(i, value);
+        }
+    }
+
+}

common/src/main/java/com/viaversion/viaversion/protocols/v1_20_3to1_20_5/rewriter/BlockItemPacketRewriter1_20_5.java

@@ -88,6 +88,7 @@ import com.viaversion.viaversion.protocols.v1_20_3to1_20_5.data.BannerPatterns1_
 import com.viaversion.viaversion.protocols.v1_20_3to1_20_5.data.DyeColors;
 import com.viaversion.viaversion.protocols.v1_20_3to1_20_5.data.Enchantments1_20_5;
 import com.viaversion.viaversion.protocols.v1_20_3to1_20_5.data.EquipmentSlots1_20_5;
+import com.viaversion.viaversion.protocols.v1_20_3to1_20_5.data.MaxStackSize1_20_3;
 import com.viaversion.viaversion.protocols.v1_20_3to1_20_5.data.Instruments1_20_3;
 import com.viaversion.viaversion.protocols.v1_20_3to1_20_5.data.MapDecorations1_20_5;
 import com.viaversion.viaversion.protocols.v1_20_3to1_20_5.data.PotionEffects1_20_5;
@@ -364,6 +365,14 @@ public final class BlockItemPacketRewriter1_20_5 extends ItemRewriter<Clientboun
         }
 
         final Item structuredItem = toStructuredItem(connection, item);
+
+        if (Via.getConfig().handleInvalidItemCount()) {
+            // Server can send amounts which are higher than vanilla's default, and 1.20.4 will still accept them,
+            // let's use the new added data key to emulate this behavior
+            if (structuredItem.amount() > MaxStackSize1_20_3.getMaxStackSize(structuredItem.identifier())) {
+                structuredItem.structuredData().set(StructuredDataKey.MAX_STACK_SIZE, structuredItem.amount());
+            }
+        }
         return super.handleItemToClient(connection, structuredItem);
     }
 

common/src/main/resources/assets/viaversion/config.yml

@@ -182,6 +182,9 @@ translate-ocelot-to-cat: false
 # It is not recommended to fake this value if your server is running 1.19 or later, as 1.20.5 have stricter chat handling and may get kicked otherwise.
 enforce-secure-chat: false
 #
+# Handles items with invalid count values (higher than max stack size) on 1.20.3 servers.
+handle-invalid-item-count: false
+#
 #----------------------------------------------------------#
 #             1.9+ CLIENTS ON 1.8 SERVERS OPTIONS          #
 #----------------------------------------------------------#