craftbukkit/nms-patches/net/minecraft/world/entity/Leashable.patch

--- a/net/minecraft/world/entity/Leashable.java
+++ b/net/minecraft/world/entity/Leashable.java
@@ -27,6 +27,11 @@
 import net.minecraft.world.phys.AxisAlignedBB;
 import net.minecraft.world.phys.Vec3D;
 
+// CraftBukkit start
+import org.bukkit.event.entity.EntityUnleashEvent;
+import org.bukkit.event.entity.EntityUnleashEvent.UnleashReason;
+// CraftBukkit end
+
 public interface Leashable {
 
     String LEASH_TAG = "leash";
@@ -68,11 +73,11 @@
 
     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
     }
 
     default void readLeashData(ValueInput valueinput) {
-        Leashable.a leashable_a = (Leashable.a) valueinput.read("leash", Leashable.a.CODEC).orElse((Object) null);
+        Leashable.a leashable_a = (Leashable.a) valueinput.read("leash", Leashable.a.CODEC).orElse(null); // CraftBukkit - decompile error
 
         if (this.getLeashData() != null && leashable_a == null) {
             this.removeLeash();
@@ -82,6 +87,14 @@
     }
 
     default void writeLeashData(ValueOutput valueoutput, @Nullable Leashable.a leashable_a) {
+        // CraftBukkit start - SPIGOT-7487: Don't save (and possible drop) leash, when the holder was removed by a plugin
+        if (leashable_a != null) {
+            Entity entity = leashable_a.leashHolder;
+            if (entity != null && entity.pluginRemoved) {
+                return;
+            }
+        }
+        // CraftBukkit end
         valueoutput.storeNullable("leash", Leashable.a.CODEC, leashable_a);
     }
 
@@ -107,7 +120,9 @@
                 }
 
                 if (e0.tickCount > 100) {
+                    e0.forceDrops = true; // CraftBukkit
                     e0.spawnAtLocation(worldserver, (IMaterial) Items.LEAD);
+                    e0.forceDrops = false; // CraftBukkit
                     ((Leashable) e0).setLeashData((Leashable.a) null);
                 }
             }
@@ -116,11 +131,11 @@
     }
 
     default void dropLeash() {
-        dropLeash((Entity) this, true, true);
+        dropLeash((Entity & Leashable) this, true, true); // CraftBukkit - decompile error
     }
 
     default void removeLeash() {
-        dropLeash((Entity) this, true, false);
+        dropLeash((Entity & Leashable) this, true, false); // CraftBukkit - decompile error
     }
 
     default void onLeashRemoved() {}
@@ -137,7 +152,9 @@
                 WorldServer worldserver = (WorldServer) world;
 
                 if (flag1) {
+                    e0.forceDrops = true; // CraftBukkit
                     e0.spawnAtLocation(worldserver, (IMaterial) Items.LEAD);
+                    e0.forceDrops = false; // CraftBukkit
                 }
 
                 if (flag) {
@@ -159,7 +176,8 @@
 
         if (leashable_a != null && leashable_a.leashHolder != null) {
             if (!e0.isAlive() || !leashable_a.leashHolder.isAlive()) {
-                if (worldserver.getGameRules().getBoolean(GameRules.RULE_DOENTITYDROPS)) {
+                worldserver.getCraftServer().getPluginManager().callEvent(new EntityUnleashEvent(e0.getBukkitEntity(), (!e0.isAlive()) ? UnleashReason.PLAYER_UNLEASH : UnleashReason.HOLDER_GONE)); // CraftBukkit
+                if (worldserver.getGameRules().getBoolean(GameRules.RULE_DOENTITYDROPS) && !e0.pluginRemoved) { // CraftBukkit - SPIGOT-7487: Don't drop leash, when the holder was removed by a plugin
                     ((Leashable) e0).dropLeash();
                 } else {
                     ((Leashable) e0).removeLeash();
@@ -211,6 +229,11 @@
     }
 
     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();
     }
 
@@ -218,7 +241,7 @@
 
     default boolean checkElasticInteractions(Entity entity, Leashable.a leashable_a) {
         boolean flag = entity.supportQuadLeashAsHolder() && this.supportQuadLeash();
-        List<Leashable.b> list = computeElasticInteraction((Entity) this, entity, flag ? Leashable.SHARED_QUAD_ATTACHMENT_POINTS : Leashable.ENTITY_ATTACHMENT_POINT, flag ? Leashable.SHARED_QUAD_ATTACHMENT_POINTS : Leashable.LEASHER_ATTACHMENT_POINT);
+        List<Leashable.b> list = computeElasticInteraction((Entity & Leashable) this, entity, flag ? Leashable.SHARED_QUAD_ATTACHMENT_POINTS : Leashable.ENTITY_ATTACHMENT_POINT, flag ? Leashable.SHARED_QUAD_ATTACHMENT_POINTS : Leashable.LEASHER_ATTACHMENT_POINT); // CraftBukkit - decompile error
 
         if (list.isEmpty()) {
             return false;
@@ -257,7 +280,7 @@
             Vec3D vec3d4 = e0.position().add(vec3d3);
             Vec3D vec3d5 = ((Vec3D) list1.get(i)).multiply(vec3d2).yRot(-f1);
             Vec3D vec3d6 = entity.position().add(vec3d5);
-            Optional optional = computeDampenedSpringInteraction(vec3d6, vec3d4, d0, vec3d, vec3d3);
+            Optional<Leashable.b> optional = computeDampenedSpringInteraction(vec3d6, vec3d4, d0, vec3d, vec3d3); // CraftBukkit - decompile error
 
             Objects.requireNonNull(list2);
             optional.ifPresent(list2::add);
@@ -314,7 +337,7 @@
 
     default void setLeashedTo(Entity entity, boolean flag) {
         if (this != entity) {
-            setLeashedTo((Entity) this, entity, flag);
+            setLeashedTo((Entity & Leashable) this, entity, flag); // CraftBukkit - decompile error
         }
     }
 
@@ -351,7 +374,7 @@
 
     @Nullable
     default Entity getLeashHolder() {
-        return getLeashHolder((Entity) this);
+        return getLeashHolder((Entity & Leashable) this); // CraftBukkit - decompile error
     }
 
     @Nullable