Predicate on callback-action to avoid NPE issues on some conditions.

Author: jamailun

api/src/main/java/fr/jamailun/ultimatespellsystem/api/entities/CallbackAction.java

@@ -8,6 +8,7 @@
 import org.jetbrains.annotations.NotNull;
 
 import java.util.function.Function;
+import java.util.function.Predicate;
 
 /**
  * An action for a callback.
@@ -20,6 +21,21 @@ public final class CallbackAction<E extends Event, A> {
     private final CallbackEvent dslDefinition;
     private final Class<E> listenedEvent;
     private final Function<E, A> argumentExtractor;
+    private final Predicate<E> conditionalPredicate;
+
+    /**
+     * Create a new callback definition.
+     * @param dslDefinition DSL definition to register.
+     * @param listenedEvent type of event to react to.
+     * @param argumentExtractor argument extractor. Must extract an argument from the event instance (matching the type).
+     * @param conditionalPredicate optional predicate to determine if the callback should be executed.
+     */
+    public CallbackAction(@NotNull CallbackEvent dslDefinition, @NotNull Class<E> listenedEvent, @NotNull Function<E, A> argumentExtractor, @NotNull Predicate<E> conditionalPredicate) {
+        this.dslDefinition = dslDefinition;
+        this.listenedEvent = listenedEvent;
+        this.argumentExtractor = argumentExtractor;
+        this.conditionalPredicate = conditionalPredicate;
+    }
 
     /**
      * Create a new callback definition.
@@ -31,6 +47,7 @@ public CallbackAction(@NotNull CallbackEvent dslDefinition, @NotNull Class<E> li
         this.dslDefinition = dslDefinition;
         this.listenedEvent = listenedEvent;
         this.argumentExtractor = argumentExtractor;
+        this.conditionalPredicate = x -> true;
     }
 
     /**
@@ -42,11 +59,16 @@ public CallbackAction(@NotNull CallbackEvent dslDefinition, @NotNull Class<E> li
      */
     public void registerToSummon(@NotNull SummonAttributes summon, String argVarName, @NotNull SpellRuntime runtime, @NotNull RuntimeStatement child) {
         summon.registerCallback(listenedEvent, (event) -> {
-            // 1. Register variable
+            // 1. Check predicate
+            if( ! conditionalPredicate.test(event))
+                return;
+
+            // 2. Register variable, if variable exists
             if(argVarName != null) {
                 runtime.variables().set(argVarName, argumentExtractor.apply(event));
             }
-            // 2. Execute child
+
+            // 3. Execute child
             child.run(runtime);
         });
     }

plugin/src/main/java/fr/jamailun/ultimatespellsystem/extension/callbacks/EntityDeathCallbacks.java

@@ -12,26 +12,26 @@
 import java.util.List;
 
 /**
- * Used by {@code LAND} callbacks.
+ * Used by {@code DIE} callbacks.
  */
 public class EntityDeathCallbacks extends CallbackProvider<EntityDeathEvent> {
 
-    @EventHandler
-    void onEvent(@NotNull EntityDeathEvent event) {
-        SummonAttributes summon = UltimateSpellSystem.getSummonsManager().find(event.getEntity().getUniqueId());
-        if(summon == null) return;
-        summon.applyCallback(event);
-    }
+  @EventHandler
+  void onEvent(@NotNull EntityDeathEvent event) {
+    SummonAttributes summon = UltimateSpellSystem.getSummonsManager().find(event.getEntity().getUniqueId());
+    if (summon != null)
+      summon.applyCallback(event);
+  }
 
-    @Override
-    public @NotNull Collection<CallbackAction<EntityDeathEvent, ?>> getCallbacks() {
-        return List.of(
-                new CallbackAction<>(
-                    CallbackEvent.of("die"),
-                    EntityDeathEvent.class,
-                    x -> null
-                )
-        );
-    }
+  @Override
+  public @NotNull Collection<CallbackAction<EntityDeathEvent, ?>> getCallbacks() {
+    return List.of(
+        new CallbackAction<>(
+            CallbackEvent.of("die"),
+            EntityDeathEvent.class,
+            x -> null
+        )
+    );
+  }
 
 }

plugin/src/main/java/fr/jamailun/ultimatespellsystem/extension/callbacks/ProjectileLandCallbacks.java

@@ -19,27 +19,31 @@
  */
 public class ProjectileLandCallbacks extends CallbackProvider<ProjectileHitEvent> {
 
-    @EventHandler
-    void onEvent(@NotNull ProjectileHitEvent event) {
-        SummonAttributes summon = UltimateSpellSystem.getSummonsManager().find(event.getEntity().getUniqueId());
-        if(summon == null) return;
-        summon.applyCallback(event);
-    }
+  @EventHandler
+  void onEvent(@NotNull ProjectileHitEvent event) {
+    SummonAttributes summon = UltimateSpellSystem.getSummonsManager().find(event.getEntity().getUniqueId());
+    if (summon != null)
+      summon.applyCallback(event);
+  }
 
-    @Override
-    public @NotNull Collection<CallbackAction<ProjectileHitEvent, ?>> getCallbacks() {
-        return List.of(
-                new CallbackAction<>(
-                    CallbackEvent.of("landed", TokenType.AT, TypePrimitive.LOCATION),
-                    ProjectileHitEvent.class,
-                    e -> e.getEntity().getLocation()
-                ),
-                new CallbackAction<>(
-                        CallbackEvent.of("hit", TokenType.TO, TypePrimitive.ENTITY),
-                        ProjectileHitEvent.class,
-                        e -> new BukkitSpellEntity(e.getHitEntity())
-                )
-        );
-    }
+  @Override
+  public @NotNull Collection<CallbackAction<ProjectileHitEvent, ?>> getCallbacks() {
+    return List.of(
+        // Always valid.
+        new CallbackAction<>(
+            CallbackEvent.of("landed", TokenType.AT, TypePrimitive.LOCATION),
+            ProjectileHitEvent.class,
+            e -> e.getEntity().getLocation().clone()
+        ),
+
+        // Hit (requires an entity)
+        new CallbackAction<>(
+            CallbackEvent.of("hit", TokenType.TO, TypePrimitive.ENTITY),
+            ProjectileHitEvent.class,
+            e -> e.getHitEntity() == null ? null : new BukkitSpellEntity(e.getHitEntity()),
+            e -> e.getHitEntity() != null // Must have an entity to be triggered
+        )
+    );
+  }
 
 }