PaperMC/paper-server/nms-patches/net/minecraft/world/item/ItemWorldMap.patch

--- a/net/minecraft/world/item/ItemWorldMap.java
+++ b/net/minecraft/world/item/ItemWorldMap.java
@@ -30,6 +30,11 @@
 import net.minecraft.world.level.material.MaterialMapColor;
 import net.minecraft.world.level.saveddata.maps.WorldMap;
 
+// CraftBukkit start
+import org.bukkit.Bukkit;
+import org.bukkit.event.server.MapInitializeEvent;
+// CraftBukkit end
+
 public class ItemWorldMap extends ItemWorldMapBase {
 
     public ItemWorldMap(Item.Info item_info) {
@@ -62,7 +67,7 @@
     public static int d(ItemStack itemstack) {
         NBTTagCompound nbttagcompound = itemstack.getTag();
 
-        return nbttagcompound != null && nbttagcompound.hasKeyOfType("map", 99) ? nbttagcompound.getInt("map") : 0;
+        return nbttagcompound != null && nbttagcompound.hasKeyOfType("map", 99) ? nbttagcompound.getInt("map") : -1; // CraftBukkit - make new maps for no tag
     }
 
     private static WorldMap a(ItemStack itemstack, World world, int i, int j, int k, boolean flag, boolean flag1, ResourceKey<World> resourcekey) {
@@ -72,6 +77,11 @@
         worldmap.a(i, j, k, flag, flag1, resourcekey);
         world.a(worldmap);
         itemstack.getOrCreateTag().setInt("map", l);
+
+        // CraftBukkit start
+        MapInitializeEvent event = new MapInitializeEvent(worldmap.mapView);
+        Bukkit.getServer().getPluginManager().callEvent(event);
+        // CraftBukkit end
         return worldmap;
     }