refactor(decorators): automatic handling of missing child

Decorators no longer require missing child logic built into them. They will always return a failure
and exit early if a child is missing.

Author: ashblue

Assets/FluidBehaviorTree/Runtime/Decorators/DecoratorBase.cs

@@ -20,6 +20,13 @@ public abstract class DecoratorBase : GenericTaskBase, ITaskParent {
 
         public override TaskStatus Update () {
             base.Update();
+
+            if (Child == null) {
+                if (Application.isPlaying) Debug.LogWarning(
+                    $"Decorator {Name} has no child. Force returning failure. Please fix");
+                return TaskStatus.Failure;
+            }
+            
             var status = OnUpdate();
             LastStatus = status;
 

Assets/FluidBehaviorTree/Runtime/Decorators/DecoratorGeneric.cs

@@ -6,10 +6,6 @@ public class DecoratorGeneric : DecoratorBase {
         public Func<ITask, TaskStatus> updateLogic;
 
         protected override TaskStatus OnUpdate () {
-            if (Child == null) {
-                return TaskStatus.Success;
-            }
-            
             if (updateLogic != null) {
                 return updateLogic(Child);
             }

Assets/FluidBehaviorTree/Runtime/Decorators/Inverter.cs

@@ -5,10 +5,6 @@ public class Inverter : DecoratorBase {
         public override string IconPath { get; } = $"{PACKAGE_ROOT}/Invert.png";
 
         protected override TaskStatus OnUpdate () {
-            if (Child == null) {
-                return TaskStatus.Success;
-            }
-
             var childStatus = Child.Update();
             var status = childStatus;
 

Assets/FluidBehaviorTree/Tests/Editor/Decorators/DecoratorTest.cs

@@ -5,6 +5,8 @@
 
 namespace CleverCrow.Fluid.BTs.Testing {
     public class DecoratorTest {
+        private DecoratorExample _decorator;
+        
         public class DecoratorExample : DecoratorBase {
             public TaskStatus status;
 
@@ -13,46 +15,49 @@ protected override TaskStatus OnUpdate () {
             }
         }
 
-        public class EnabledProperty {
+        [SetUp]
+        public void BeforeEach () {
+            _decorator = new DecoratorExample();
+            _decorator.AddChild(A.TaskStub().Build());
+        }
+
+        public class EnabledProperty : DecoratorTest {
             [Test]
             public void Returns_true_if_child_is_set () {
-                var decorator = new DecoratorExample();
-                decorator.AddChild(A.TaskStub().Build());
-                
-                Assert.IsTrue(decorator.Enabled);
+                Assert.IsTrue(_decorator.Enabled);
             }
 
             [Test]
             public void Returns_false_if_child_is_set_but_set_to_false () {
-                var decorator = new DecoratorExample();
-                decorator.AddChild(A.TaskStub().Build());
-                decorator.Enabled = false;
+                _decorator.Enabled = false;
 
-                Assert.IsFalse(decorator.Enabled);
+                Assert.IsFalse(_decorator.Enabled);
             }
         }
 
-        public class UpdateMethod {
+        public class UpdateMethod : DecoratorTest {
             [Test]
             public void Sets_LastUpdate_to_returned_status_value () {
-                var decorator = new DecoratorExample();
-                decorator.status = TaskStatus.Failure;
+                _decorator.status = TaskStatus.Failure;
+
+                _decorator.Update();
 
-                decorator.Update();
+                Assert.AreEqual(TaskStatus.Failure, _decorator.LastStatus);
+            }
 
-                Assert.AreEqual(TaskStatus.Failure, decorator.LastStatus);
+            [Test]
+            public void It_should_return_failure_if_a_child_is_missing () {
+                _decorator.Children.RemoveAt(0);
+                Assert.AreEqual(TaskStatus.Failure, _decorator.Update());
             }
         }
 
-        public class EndMethod {
+        public class EndMethod : DecoratorTest {
             [Test]
             public void Calls_end_on_child () {
-                var decorator = new DecoratorExample();
-                decorator.AddChild(A.TaskStub().Build());
-
-                decorator.End();
+                _decorator.End();
 
-                decorator.Child.Received(1).End();
+                _decorator.Child.Received(1).End();
             }
         }
     }

Assets/FluidBehaviorTree/Tests/Editor/Decorators/InverterTest.cs

@@ -28,13 +28,6 @@ public void Returns_continue_when_child_returns_continue () {
 
                 Assert.AreEqual(TaskStatus.Continue, inverter.Update());
             }
-
-            [Test]
-            public void Does_not_crash_if_no_child () {
-                var inverter = new Inverter();
-
-                inverter.Update();
-            }
         }
     }
 }