PaperMC/patches/unapplied/server/0723-Fix-incosistency-issue-with-empty-map-items-in-CB.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Shane Freeder <theboyetronic@gmail.com>
Date: Sun, 1 Aug 2021 09:49:06 +0100
Subject: [PATCH] Fix incosistency issue with empty map items in CB


diff --git a/src/main/java/net/minecraft/world/item/MapItem.java b/src/main/java/net/minecraft/world/item/MapItem.java
index 24700c7e6a32cc30c97dccc21c5f3e3e6b6438e5..4365d8bd4b5c63c1d112b3cd68b6c7163aa56600 100644
--- a/src/main/java/net/minecraft/world/item/MapItem.java
+++ b/src/main/java/net/minecraft/world/item/MapItem.java
@@ -72,7 +72,7 @@ public class MapItem extends ComplexItem {
     public static Integer getMapId(ItemStack stack) {
         CompoundTag nbttagcompound = stack.getTag();
 
-        return nbttagcompound != null && nbttagcompound.contains("map", 99) ? nbttagcompound.getInt("map") : -1; // CraftBukkit - make new maps for no tag
+        return nbttagcompound != null && nbttagcompound.contains("map", 99) ? nbttagcompound.getInt("map") : null; // CraftBukkit - make new maps for no tag // Paper - don't return invalid ID
     }
 
     public static int createNewSavedData(Level world, int x, int z, int scale, boolean showIcons, boolean unlimitedTracking, ResourceKey<Level> dimension) {
diff --git a/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaMap.java b/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaMap.java
index 96ab7d53f4e089c7666872f9fd0f09283259a726..8e634ccb91b58000412c572903e57d30ddb2caba 100644
--- a/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaMap.java
+++ b/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaMap.java
@@ -144,6 +144,7 @@ class CraftMetaMap extends CraftMetaItem implements MapMeta {
 
     @Override
     public int getMapId() {
+        Preconditions.checkState(this.hasMapView(), "Item does not have map associated - check hasMapView() first!"); // Paper - more friendly message
         return this.mapId;
     }