SPIGOT-1588: Fix cancelling mount related events

nms-patches/Entity.patch

@@ -449,6 +449,15 @@
              EntityItem entityitem = new EntityItem(this.world, this.locX, this.locY + (double) f, this.locZ, itemstack);
  
              entityitem.n();
+@@ -1678,7 +1963,7 @@
+             Entity entity = this.ax;
+ 
+             this.ax = null;
+-            entity.p(this);
++            if (!entity.p(this)) this.ax = entity; // CraftBukkit
+         }
+ 
+     }
 @@ -1687,6 +1972,24 @@
          if (entity.getVehicle() != this) {
              throw new IllegalStateException("Use x.startRiding(y), not y.addPassenger(x)");
@@ -474,7 +483,12 @@
              if (!this.world.isClientSide && entity instanceof EntityHuman && !(this.bO() instanceof EntityHuman)) {
                  this.passengers.add(0, entity);
              } else {
-@@ -1700,6 +2003,22 @@
+@@ -1696,13 +1999,30 @@
+         }
+     }
+ 
+-    protected void p(Entity entity) {
++    protected boolean p(Entity entity) { // CraftBukkit
          if (entity.getVehicle() == this) {
              throw new IllegalStateException("Use x.stopRiding(y), not y.removePassenger(x)");
          } else {
@@ -490,14 +504,18 @@
 +                CraftEntity craftn = (CraftEntity) entity.getBukkitEntity().getVehicle();
 +                Entity n = craftn == null ? null : craftn.getHandle();
 +                if (event.isCancelled() || n != orig) {
-+                    return;
++                    return false;
 +                }
 +            }
 +            // CraftBukkit end
              this.passengers.remove(entity);
              entity.k = 60;
          }
-@@ -1799,6 +2118,13 @@
++        return true; // CraftBukkit
+     }
+ 
+     protected boolean q(Entity entity) {
+@@ -1799,6 +2119,13 @@
      }
  
      public void setSwimming(boolean flag) {
@@ -511,7 +529,7 @@
          this.setFlag(4, flag);
      }
  
-@@ -1859,14 +2185,49 @@
+@@ -1859,14 +2186,49 @@
      }
  
      public void setAirTicks(int i) {
@@ -564,7 +582,7 @@
          }
  
      }
-@@ -2035,19 +2396,76 @@
+@@ -2035,19 +2397,76 @@
          if (!this.world.isClientSide && !this.dead) {
              this.world.methodProfiler.a("changeDimension");
              MinecraftServer minecraftserver = this.bK();
@@ -644,7 +662,7 @@
              BlockPosition blockposition;
  
              if (i == 1) {
-@@ -2076,12 +2494,18 @@
+@@ -2076,12 +2495,18 @@
                  blockposition = new BlockPosition(this);
              }
  
@@ -664,7 +682,7 @@
                  if (j == 1 && i == 1) {
                      BlockPosition blockposition1 = worldserver1.getHighestBlockYAt(HeightMap.Type.MOTION_BLOCKING_NO_LEAVES, worldserver1.getSpawn());
  
-@@ -2089,6 +2513,7 @@
+@@ -2089,6 +2514,7 @@
                  } else {
                      entity.setPositionRotation(blockposition, entity.yaw, entity.pitch);
                  }
@@ -672,7 +690,7 @@
  
                  boolean flag = entity.attachedToPlayer;
  
-@@ -2096,13 +2521,21 @@
+@@ -2096,13 +2522,21 @@
                  worldserver1.addEntity(entity);
                  entity.attachedToPlayer = flag;
                  worldserver1.entityJoinedWorld(entity, false);
@@ -695,7 +713,7 @@
              return entity;
          } else {
              return null;
-@@ -2242,7 +2675,26 @@
+@@ -2242,7 +2676,26 @@
      }
  
      public void a(AxisAlignedBB axisalignedbb) {