Correctly fire VehicleExitEvent. Fixes BUKKIT-3761

This change makes it so that EntityHuman#setPassengerOf(Entity) invokes
its parent method when leaving vehicles so that VehicleExitEvent is fired
for players leaving vehicles.

This change also fixes BUKKIT-2110, making it so VehicleExitEvent
correctly handles cancellation. The implementation of VehicleExitEvent
completely ignored the cancellation state of the event, making it so that
cancelling the event had no effect.  Cancelling a VehicleExitEvent now
causes the entity to remain inside of the vehicle, with no visual stutter.

1 files changed, 25 insertions, 1 deletions

diff --git a/src/main/java/net/minecraft/server/Entity.java b/src/main/java/net/minecraft/server/Entity.java
index 671384d5..50edbdb5 100644
--- a/src/main/java/net/minecraft/server/Entity.java
+++ b/src/main/java/net/minecraft/server/Entity.java
@@ -1391,6 +1391,8 @@ public abstract class Entity {
         // b(null) doesn't really fly for overloaded methods,
         // so this method is needed
 
+        Entity originalVehicle = this.vehicle;
+        Entity originalPassenger = this.vehicle == null ? null : this.vehicle.passenger;
         PluginManager pluginManager = Bukkit.getPluginManager();
         this.getBukkitEntity(); // make sure bukkitEntity is initialised
         // CraftBukkit end
@@ -1402,6 +1404,10 @@ public abstract class Entity {
                 if ((this.bukkitEntity instanceof LivingEntity) && (this.vehicle.getBukkitEntity() instanceof Vehicle)) {
                     VehicleExitEvent event = new VehicleExitEvent((Vehicle) this.vehicle.getBukkitEntity(), (LivingEntity) this.bukkitEntity);
                     pluginManager.callEvent(event);
+
+                    if (event.isCancelled() || this.vehicle != originalVehicle) {
+                        return;
+                    }
                 }
                 // CraftBukkit end
 
@@ -1413,10 +1419,28 @@ public abstract class Entity {
         } else {
             // CraftBukkit start
             if ((this.bukkitEntity instanceof LivingEntity) && (entity.getBukkitEntity() instanceof Vehicle) && entity.world.isChunkLoaded((int) entity.locX >> 4, (int) entity.locZ >> 4)) {
+                // It's possible to move from one vehicle to another.  We need to check if they're already in a vehicle, and fire an exit event if they are.
+                VehicleExitEvent exitEvent = null;
+                if (this.vehicle != null) {
+                    exitEvent = new VehicleExitEvent((Vehicle) this.vehicle.getBukkitEntity(), (LivingEntity) this.bukkitEntity);
+                    pluginManager.callEvent(exitEvent);
+
+                    if (exitEvent.isCancelled() || this.vehicle != originalVehicle || (this.vehicle != null && this.vehicle.passenger != originalPassenger)) {
+                        return;
+                    }
+                }
+
                 VehicleEnterEvent event = new VehicleEnterEvent((Vehicle) entity.getBukkitEntity(), this.bukkitEntity);
                 pluginManager.callEvent(event);
 
-                if (event.isCancelled()) {
+                // If a plugin messes with the vehicle or the vehicle's passenger
+                if (event.isCancelled() || this.vehicle != originalVehicle || (this.vehicle != null && this.vehicle.passenger != originalPassenger)) {
+                    // If we only cancelled the enterevent then we need to put the player in a decent position.
+                    if (exitEvent != null && this.vehicle == originalVehicle && this.vehicle != null && this.vehicle.passenger == originalPassenger) {
+                        this.setPositionRotation(this.vehicle.locX, this.vehicle.boundingBox.b + (double) this.vehicle.length, this.vehicle.locZ, this.yaw, this.pitch);
+                        this.vehicle.passenger = null;
+                        this.vehicle = null;
+                    }
                     return;
                 }
             }