✨ Add error check for multiple apiTypes for the reconciliation

pkg/builder/controller.go

@@ -59,13 +59,18 @@ func ControllerManagedBy(m manager.Manager) *Builder {
 type ForInput struct {
 	object     runtime.Object
 	predicates []predicate.Predicate
+	err        error
 }
 
 // For defines the type of Object being *reconciled*, and configures the ControllerManagedBy to respond to create / delete /
 // update events by *reconciling the object*.
 // This is the equivalent of calling
 // Watches(&source.Kind{Type: apiType}, &handler.EnqueueRequestForObject{})
 func (blder *Builder) For(object runtime.Object, opts ...ForOption) *Builder {
+	if blder.forInput.object != nil {
+		blder.forInput.err = fmt.Errorf("For(...) should only be called once, could not assign multiple objects for reconciliation")
+		return blder
+	}
 	input := ForInput{object: object}
 	for _, opt := range opts {
 		opt.ApplyToFor(&input)
@@ -159,6 +164,9 @@ func (blder *Builder) Build(r reconcile.Reconciler) (controller.Controller, erro
 	if blder.mgr == nil {
 		return nil, fmt.Errorf("must provide a non-nil Manager")
 	}
+	if blder.forInput.err != nil {
+		return nil, blder.forInput.err
+	}
 
 	// Set the Config
 	blder.loadRestConfig()

pkg/builder/controller_test.go

@@ -90,6 +90,20 @@ var _ = Describe("application", func() {
 			Expect(instance).NotTo(BeNil())
 		})
 
+		It("should return error if given two apiType objects in For function", func() {
+			By("creating a controller manager")
+			m, err := manager.New(cfg, manager.Options{})
+			Expect(err).NotTo(HaveOccurred())
+
+			instance, err := ControllerManagedBy(m).
+				For(&appsv1.ReplicaSet{}).
+				For(&appsv1.Deployment{}).
+				Owns(&appsv1.ReplicaSet{}).
+				Build(noop)
+			Expect(err).To(MatchError(ContainSubstring("For(...) should only be called once, could not assign multiple objects for reconciliation")))
+			Expect(instance).To(BeNil())
+		})
+
 		It("should return an error if there is no GVK for an object, and thus we can't default the controller name", func() {
 			By("creating a controller manager")
 			m, err := manager.New(cfg, manager.Options{})