Add unsupported config option and internal API to simplify remote item matching

This is important for 1.21.5 servers/clients and non-Vanilla clients that may not be able to match 1.21.5 data hashes anymore

paper-server/patches/sources/net/minecraft/server/level/ServerPlayer.java.patch

@@ -10,7 +10,7 @@
      @Nullable
      private Vec3 startingToFallPosition;
      @Nullable
-@@ -258,6 +_,13 @@
+@@ -258,6 +_,20 @@
              }
          }
  
@@ -20,6 +20,13 @@
 +            ServerPlayer.this.connection.send(new ClientboundContainerSetSlotPacket(ServerPlayer.this.inventoryMenu.containerId, ServerPlayer.this.inventoryMenu.incrementStateId(), net.minecraft.world.inventory.InventoryMenu.SHIELD_SLOT, ServerPlayer.this.inventoryMenu.getSlot(net.minecraft.world.inventory.InventoryMenu.SHIELD_SLOT).getItem().copy()));
 +        }
 +        // Paper end - Sync offhand slot in menus
++
++        // Paper start - add flag to simplify remote matching logic
++        @Override
++        public ServerPlayer player() {
++            return ServerPlayer.this;
++        }
++        // Paper end - add flag to simplify remote matching logic
 +
          @Override
          public void sendSlotChange(AbstractContainerMenu container, int slot, ItemStack itemStack) {

paper-server/patches/sources/net/minecraft/world/inventory/AbstractContainerMenu.java.patch

@@ -72,6 +72,41 @@
              }
          }
      }
+@@ -243,7 +_,7 @@
+     private void synchronizeSlotToRemote(int slotIndex, ItemStack stack, Supplier<ItemStack> supplier) {
+         if (!this.suppressRemoteUpdates) {
+             ItemStack itemStack = this.remoteSlots.get(slotIndex);
+-            if (!ItemStack.matches(itemStack, stack)) {
++            if (!this.matchesRemote(itemStack, stack)) { // Paper - add flag to simplify remote matching logic
+                 ItemStack itemStack1 = supplier.get();
+                 this.remoteSlots.set(slotIndex, itemStack1);
+                 if (this.synchronizer != null) {
+@@ -267,7 +_,7 @@
+ 
+     private void synchronizeCarriedToRemote() {
+         if (!this.suppressRemoteUpdates) {
+-            if (!ItemStack.matches(this.getCarried(), this.remoteCarried)) {
++            if (!this.matchesRemote(this.getCarried(), this.remoteCarried)) { // Paper - add flag to simplify remote matching logic
+                 this.remoteCarried = this.getCarried().copy();
+                 if (this.synchronizer != null) {
+                     this.synchronizer.sendCarriedChange(this, this.remoteCarried);
+@@ -276,6 +_,16 @@
+         }
+     }
+ 
++    // Paper start - add flag to simplify remote matching logic
++    private boolean matchesRemote(final ItemStack stack, final ItemStack other) {
++        if (this.synchronizer != null && this.synchronizer.player() != null && this.synchronizer.player().getBukkitEntity().simplifyContainerDesyncCheck()) {
++            // Only check the item type and count
++            return stack == other || (stack.getCount() == other.getCount() && ItemStack.isSameItem(stack, other));
++        }
++        return ItemStack.matches(stack, other);
++    }
++    // Paper end - add flag to simplify remote matching logic
++
+     public void setRemoteSlot(int slot, ItemStack stack) {
+         this.remoteSlots.set(slot, stack.copy());
+     }
 @@ -343,6 +_,7 @@
                      this.resetQuickCraft();
                  }

paper-server/patches/sources/net/minecraft/world/inventory/ContainerSynchronizer.java.patch

@@ -1,9 +1,15 @@
 --- a/net/minecraft/world/inventory/ContainerSynchronizer.java
 +++ b/net/minecraft/world/inventory/ContainerSynchronizer.java
-@@ -11,4 +_,6 @@
+@@ -11,4 +_,12 @@
      void sendCarriedChange(AbstractContainerMenu containerMenu, ItemStack stack);
  
      void sendDataChange(AbstractContainerMenu container, int id, int value);
 +
 +    default void sendOffHandSlotChange() {} // Paper - Sync offhand slot in menus
++
++    // Paper start - add flag to simplify remote matching logic
++    default net.minecraft.server.level.@org.jspecify.annotations.Nullable ServerPlayer player() {
++        return null;
++    }
++    // Paper end - add flag to simplify remote matching logic
  }

paper-server/src/main/java/io/papermc/paper/configuration/GlobalConfiguration.java

@@ -186,6 +186,8 @@ public class GlobalConfiguration extends ConfigurationPart {
         public CompressionFormat compressionFormat = CompressionFormat.ZLIB;
         @Comment("This setting controls if equipment should be updated when handling certain player actions.")
         public boolean updateEquipmentOnPlayerActions = true;
+        @Comment("Only checks an item's amount and type instead of its full data during inventory desync checks.")
+        public boolean simplifyRemoteItemMatching = false;
 
         public enum CompressionFormat {
             GZIP,

paper-server/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java

@@ -8,6 +8,7 @@ import com.mojang.authlib.GameProfile;
 import com.mojang.datafixers.util.Pair;
 import io.netty.buffer.Unpooled;
 import io.papermc.paper.FeatureHooks;
+import io.papermc.paper.configuration.GlobalConfiguration;
 import io.papermc.paper.entity.LookAnchor;
 import io.papermc.paper.entity.PaperPlayerGiveResult;
 import io.papermc.paper.entity.PlayerGiveResult;
@@ -225,6 +226,7 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
     private BorderChangeListener clientWorldBorderListener = this.createWorldBorderListener();
     public org.bukkit.event.player.PlayerResourcePackStatusEvent.Status resourcePackStatus; // Paper - more resource pack API
     private static final boolean DISABLE_CHANNEL_LIMIT = System.getProperty("paper.disableChannelLimit") != null; // Paper - add a flag to disable the channel limit
+    private boolean simplifyContainerDesyncCheck = GlobalConfiguration.get().unsupportedSettings.simplifyRemoteItemMatching;
     private long lastSaveTime; // Paper - getLastPlayed replacement API
 
     public CraftPlayer(CraftServer server, ServerPlayer entity) {
@@ -3606,4 +3608,20 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
     public void setDeathScreenScore(final int score) {
         getHandle().setScore(score);
     }
+
+    /**
+     * Returns whether container desync checks should skip the full item comparison of remote carried and changed slots
+     * and should instead only check their type and amount.
+     * <p>
+     * This is useful if the client is not able to produce the same item stack (or as of 1.21.5, its data hashes) as the server.
+     *
+     * @return whether to simplify container desync checks
+     */
+    public boolean simplifyContainerDesyncCheck() {
+        return simplifyContainerDesyncCheck;
+    }
+
+    public void setSimplifyContainerDesyncCheck(final boolean simplifyContainerDesyncCheck) {
+        this.simplifyContainerDesyncCheck = simplifyContainerDesyncCheck;
+    }
 }