Clone mutables to prevent unexpected issues

There are lots of locations in the API where mutable
types are not cloned, either on return or when passed
as a parameter and assigned to a field, which can cause
unexpected behaviors. Let this be a lesson to use
immutable types for simple things Location, Vector, and
others.

paper-api/src/main/java/org/bukkit/event/block/BlockCanBuildEvent.java

@@ -102,7 +102,7 @@ public class BlockCanBuildEvent extends BlockEvent {
      */
     @NotNull
     public BlockData getBlockData() {
-        return blockData;
+        return blockData.clone(); // Paper - clone because mutation isn't used
     }
 
     /**

paper-api/src/main/java/org/bukkit/event/entity/EntityChangeBlockEvent.java

@@ -61,7 +61,7 @@ public class EntityChangeBlockEvent extends EntityEvent implements Cancellable {
      */
     @NotNull
     public BlockData getBlockData() {
-        return to;
+        return to.clone(); // Paper - clone because mutation isn't used
     }
 
     @NotNull

paper-api/src/main/java/org/bukkit/event/entity/EntityExplodeEvent.java

@@ -72,7 +72,7 @@ public class EntityExplodeEvent extends EntityEvent implements Cancellable {
      */
     @NotNull
     public Location getLocation() {
-        return location;
+        return location.clone(); // Paper - clone to avoid changes
     }
 
     /**

paper-api/src/main/java/org/bukkit/event/entity/EntityPortalEnterEvent.java

@@ -35,7 +35,7 @@ public class EntityPortalEnterEvent extends EntityEvent implements org.bukkit.ev
      */
     @NotNull
     public Location getLocation() {
-        return location;
+        return location.clone(); // Paper - clone to avoid changes
     }
 
     // Paper start

paper-api/src/main/java/org/bukkit/event/entity/ItemDespawnEvent.java

@@ -46,7 +46,7 @@ public class ItemDespawnEvent extends EntityEvent implements Cancellable {
      */
     @NotNull
     public Location getLocation() {
-        return location;
+        return location.clone(); // Paper - clone to avoid changes
     }
 
     @NotNull

paper-api/src/main/java/org/bukkit/event/vehicle/VehicleBlockCollisionEvent.java

@@ -31,7 +31,7 @@ public class VehicleBlockCollisionEvent extends VehicleCollisionEvent {
      */
     @NotNull
     public org.bukkit.util.Vector getVelocity() {
-        return velocity;
+        return velocity.clone();
     }
     // Paper end
 

paper-api/src/main/java/org/bukkit/event/vehicle/VehicleMoveEvent.java

@@ -27,7 +27,7 @@ public class VehicleMoveEvent extends VehicleEvent {
      */
     @NotNull
     public Location getFrom() {
-        return from;
+        return from.clone(); // Paper - clone to avoid changes
     }
 
     /**
@@ -37,7 +37,7 @@ public class VehicleMoveEvent extends VehicleEvent {
      */
     @NotNull
     public Location getTo() {
-        return to;
+        return to.clone(); // Paper - clone to avoid changes
     }
 
 

paper-api/src/main/java/org/bukkit/event/world/GenericGameEvent.java

@@ -49,7 +49,7 @@ public class GenericGameEvent extends WorldEvent implements Cancellable {
      */
     @NotNull
     public Location getLocation() {
-        return location;
+        return location.clone(); // Paper - clone to avoid changes
     }
 
     /**

paper-api/src/main/java/org/bukkit/event/world/SpawnChangeEvent.java

@@ -25,7 +25,7 @@ public class SpawnChangeEvent extends WorldEvent {
      */
     @NotNull
     public Location getPreviousLocation() {
-        return previousLocation;
+        return previousLocation.clone(); // Paper - clone to avoid changes
     }
 
     @NotNull

paper-api/src/main/java/org/bukkit/event/world/StructureGrowEvent.java

@@ -39,7 +39,7 @@ public class StructureGrowEvent extends WorldEvent implements Cancellable {
      */
     @NotNull
     public Location getLocation() {
-        return location;
+        return location.clone(); // Paper - clone to avoid changes
     }
 
     /**