Provide helpful error message if informer isn't found in manager.

Author: pwittrock

pkg/controller/informers/informersindex.go

@@ -17,9 +17,9 @@ limitations under the License.
 package informers
 
 import (
+	"fmt"
 	"reflect"
 
-	"fmt"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/client-go/tools/cache"
 )

pkg/controller/listeningqueue.go

@@ -68,7 +68,8 @@ func (q *listeningQueue) addEventHandler(obj metav1.Object, eh eventhandlers.Eve
 func (q *listeningQueue) lookupInformer(obj metav1.Object) (cache.SharedInformer, error) {
 	i := q.informerProvider.GetInformer(obj)
 	if i == nil {
-		return i, fmt.Errorf("Could not find SharedInformer for %T in %s", obj, q.informerProvider)
+		return i, fmt.Errorf("Could not find SharedInformer for %T in %s.  Must register with "+
+			"// +kubebuilder:informer:", obj, q.informerProvider)
 	}
 	return i, nil
 }

pkg/controller/manager.go

@@ -18,6 +18,10 @@ package controller
 
 import (
 	"fmt"
+	"os"
+	"reflect"
+	"runtime"
+	"strings"
 	"sync"
 
 	"github.com/kubernetes-sigs/kubebuilder/pkg/controller/informers"
@@ -68,7 +72,11 @@ func AddInformerProvider(object metav1.Object, informerProvider informers.Inform
 // GetInformer returns the Informer for an object
 func (m *ControllerManager) GetInformer(object metav1.Object) cache.SharedInformer {
 	m.once.Do(m.init)
-	return m.sharedInformersByResource.Get(object)
+	si := m.sharedInformersByResource.Get(object)
+	if si == nil {
+		warningMissingInformer(object)
+	}
+	return si
 }
 
 // GetInformerProvider returns the InformerProvider for the object type
@@ -129,3 +137,52 @@ func RunInformersAndControllers(options run.RunArguments) {
 func (m *ControllerManager) String() string {
 	return fmt.Sprintf("ControllerManager SharedInformers: %v", m.sharedInformersByResource)
 }
+
+// warningMissingInformer prints a warning message to stderr that an informer was not registered
+func warningMissingInformer(obj interface{}) {
+	// Get the type of the object
+	t := reflect.TypeOf(reflect.Indirect(reflect.ValueOf(obj)).Interface())
+
+	// Parse the GVK from the object
+	path := t.PkgPath()
+	groupversion := strings.Split(path, "/")
+	group := groupversion[len(groupversion)-2]
+	version := groupversion[len(groupversion)-1]
+	kind := t.Name()
+
+	// Create a helpful error message
+	msg := fmt.Sprintf("\nWARNING: %s\nWARNING: Informer for %s.%s.%s not registered!  "+
+		"Must register informer with a // +kubebuilder:informers:group=%s,version=%s,kind=%s annotation on the"+
+		"Controller struct.\n",
+		provideControllerLine(), group, version, kind, group, version, kind)
+	fmt.Fprint(os.Stderr, msg)
+}
+
+// provideControllerLine returns a string with the file and line number where "ProvideController" was called
+// in the call stack
+func provideControllerLine() string {
+	ok := true
+	var file string
+	var pc uintptr
+	var line int
+	for i := 0; ok; i++ {
+		pc, file, line, ok = runtime.Caller(i)
+		if !ok {
+			break
+		}
+		f := runtime.FuncForPC(pc)
+		if f == nil {
+			ok = false
+			break
+		}
+		parts := strings.Split(f.Name(), ".")
+		fn := parts[len(parts)-1]
+		if fn == "ProvideController" {
+			break
+		}
+	}
+	if ok {
+		return fmt.Sprintf("%s:%v", file, line)
+	}
+	return ""
+}