PaperMC/paper-server/nms-patches/net/minecraft/world/entity/Leashable.patch

--- a/net/minecraft/world/entity/Leashable.java
+++ b/net/minecraft/world/entity/Leashable.java
@@ -15,6 +15,11 @@
 import net.minecraft.world.level.IMaterial;
 import net.minecraft.world.level.World;
 
+// CraftBukkit start
+import org.bukkit.event.entity.EntityUnleashEvent;
+import org.bukkit.event.entity.EntityUnleashEvent.UnleashReason;
+// CraftBukkit end
+
 public interface Leashable {
 
     String LEASH_TAG = "leash";
@@ -44,7 +49,7 @@
 
     default void setDelayedLeashHolderId(int i) {
         this.setLeashData(new Leashable.a(i));
-        dropLeash((Entity) this, false, false);
+        dropLeash((Entity & Leashable) this, false, false); // CraftBukkit - decompile error
     }
 
     @Nullable
@@ -53,7 +58,7 @@
             return new Leashable.a(Either.left(nbttagcompound.getCompound("leash").getUUID("UUID")));
         } else {
             if (nbttagcompound.contains("leash", 11)) {
-                Either<UUID, BlockPosition> either = (Either) GameProfileSerializer.readBlockPos(nbttagcompound, "leash").map(Either::right).orElse((Object) null);
+                Either<UUID, BlockPosition> either = (Either) GameProfileSerializer.readBlockPos(nbttagcompound, "leash").map(Either::right).orElse(null); // CraftBukkit - decompile error
 
                 if (either != null) {
                     return new Leashable.a(either);
@@ -68,6 +73,11 @@
         if (leashable_a != null) {
             Either<UUID, BlockPosition> either = leashable_a.delayedLeashInfo;
             Entity entity = leashable_a.leashHolder;
+            // CraftBukkit start - SPIGOT-7487: Don't save (and possible drop) leash, when the holder was removed by a plugin
+            if (entity != null && entity.pluginRemoved) {
+                return;
+            }
+            // CraftBukkit end
 
             if (entity instanceof EntityLeash) {
                 EntityLeash entityleash = (EntityLeash) entity;
@@ -110,7 +120,9 @@
                 }
 
                 if (e0.tickCount > 100) {
+                    e0.forceDrops = true; // CraftBukkit
                     e0.spawnAtLocation((IMaterial) Items.LEAD);
+                    e0.forceDrops = false; // CraftBukkit
                     ((Leashable) e0).setLeashData((Leashable.a) null);
                 }
             }
@@ -119,7 +131,7 @@
     }
 
     default void dropLeash(boolean flag, boolean flag1) {
-        dropLeash((Entity) this, flag, flag1);
+        dropLeash((Entity & Leashable) this, flag, flag1); // CraftBukkit - decompile error
     }
 
     private static <E extends Entity & Leashable> void dropLeash(E e0, boolean flag, boolean flag1) {
@@ -128,7 +140,9 @@
         if (leashable_a != null && leashable_a.leashHolder != null) {
             ((Leashable) e0).setLeashData((Leashable.a) null);
             if (!e0.level().isClientSide && flag1) {
+                e0.forceDrops = true; // CraftBukkit
                 e0.spawnAtLocation((IMaterial) Items.LEAD);
+                e0.forceDrops = false; // CraftBukkit
             }
 
             if (flag) {
@@ -153,7 +167,8 @@
 
         if (leashable_a != null && leashable_a.leashHolder != null) {
             if (!e0.isAlive() || !leashable_a.leashHolder.isAlive()) {
-                dropLeash(e0, true, true);
+                e0.level().getCraftServer().getPluginManager().callEvent(new EntityUnleashEvent(e0.getBukkitEntity(), (!e0.isAlive()) ? UnleashReason.PLAYER_UNLEASH : UnleashReason.HOLDER_GONE)); // CraftBukkit
+                dropLeash(e0, true, !e0.pluginRemoved); // CraftBukkit - SPIGOT-7487: Don't drop leash, when the holder was removed by a plugin
             }
 
             Entity entity = ((Leashable) e0).getLeashHolder();
@@ -183,13 +198,18 @@
     }
 
     default void leashTooFarBehaviour() {
+        // CraftBukkit start
+        if (this instanceof Entity entity) {
+            entity.level().getCraftServer().getPluginManager().callEvent(new EntityUnleashEvent(entity.getBukkitEntity(), EntityUnleashEvent.UnleashReason.DISTANCE));
+        }
+        // CraftBukkit end
         this.dropLeash(true, true);
     }
 
     default void closeRangeLeashBehaviour(Entity entity) {}
 
     default void elasticRangeLeashBehaviour(Entity entity, float f) {
-        legacyElasticRangeLeashBehaviour((Entity) this, entity, f);
+        legacyElasticRangeLeashBehaviour((Entity & Leashable) this, entity, f); // CraftBukkit - decompile error
     }
 
     private static <E extends Entity & Leashable> void legacyElasticRangeLeashBehaviour(E e0, Entity entity, float f) {
@@ -201,7 +221,7 @@
     }
 
     default void setLeashedTo(Entity entity, boolean flag) {
-        setLeashedTo((Entity) this, entity, flag);
+        setLeashedTo((Entity & Leashable) this, entity, flag); // CraftBukkit - decompile error
     }
 
     private static <E extends Entity & Leashable> void setLeashedTo(E e0, Entity entity, boolean flag) {
@@ -232,7 +252,7 @@
 
     @Nullable
     default Entity getLeashHolder() {
-        return getLeashHolder((Entity) this);
+        return getLeashHolder((Entity & Leashable) this); // CraftBukkit - decompile error
     }
 
     @Nullable