Remove waypoint provider goal when providers change

src/main/java/net/citizensnpcs/trait/waypoint/GuidedWaypointProvider.java

@@ -138,6 +138,11 @@ public class GuidedWaypointProvider implements WaypointProvider {
         rebuildTree();
     }
 
+    @Override
+    public void onRemove() {
+        npc.getDefaultGoalController().removeGoal(currentGoal);
+    }
+
     @Override
     public void onSpawn(NPC npc) {
         this.npc = npc;

src/main/java/net/citizensnpcs/trait/waypoint/LinearWaypointProvider.java

@@ -86,6 +86,11 @@ public class LinearWaypointProvider implements WaypointProvider {
         }
     }
 
+    @Override
+    public void onRemove() {
+        npc.getDefaultGoalController().removeGoal(currentGoal);
+    }
+
     @Override
     public void onSpawn(NPC npc) {
         this.npc = npc;

src/main/java/net/citizensnpcs/trait/waypoint/WanderWaypointProvider.java

@@ -12,6 +12,7 @@ import org.bukkit.entity.Player;
 
 public class WanderWaypointProvider implements WaypointProvider {
     private Goal currentGoal;
+    private NPC npc;
     private volatile boolean paused;
     @Persist
     private final int xrange = DEFAULT_XRANGE;
@@ -42,8 +43,14 @@ public class WanderWaypointProvider implements WaypointProvider {
     public void load(DataKey key) {
     }
 
+    @Override
+    public void onRemove() {
+        npc.getDefaultGoalController().removeGoal(currentGoal);
+    }
+
     @Override
     public void onSpawn(NPC npc) {
+        this.npc = npc;
         if (currentGoal == null) {
             currentGoal = WanderGoal.createWithNPCAndRange(npc, xrange, yrange);
             CitizensAPI.registerEvents(currentGoal);
@@ -61,5 +68,6 @@ public class WanderWaypointProvider implements WaypointProvider {
     }
 
     private static final int DEFAULT_XRANGE = 3;
+
     private static final int DEFAULT_YRANGE = 25;
 }

src/main/java/net/citizensnpcs/trait/waypoint/WaypointProvider.java

@@ -33,6 +33,11 @@ public interface WaypointProvider {
      */
     public void load(DataKey key);
 
+    /**
+     * Called when the provider is removed from the NPC.
+     */
+    public void onRemove();
+
     /**
      * Called when the {@link NPC} attached to this provider is spawned.
      * 

src/main/java/net/citizensnpcs/trait/waypoint/Waypoints.java

@@ -81,8 +81,9 @@ public class Waypoints extends Trait {
 
     @Override
     public void onSpawn() {
-        if (provider != null)
+        if (provider != null) {
             provider.onSpawn(getNPC());
+        }
     }
 
     @Override
@@ -105,14 +106,15 @@ public class Waypoints extends Trait {
     public boolean setWaypointProvider(String name) {
         name = name.toLowerCase();
         Class<? extends WaypointProvider> clazz = providers.get(name);
-        if (clazz == null)
+        if (provider != null) {
-            return false;
+            provider.onRemove();
-        provider = create(clazz);
+        }
-        if (provider == null)
+        if (clazz == null || (provider = create(clazz)) == null)
             return false;
         providerName = name;
-        if (npc != null && npc.isSpawned())
+        if (npc != null && npc.isSpawned()) {
             provider.onSpawn(npc);
+        }
         return true;
     }