🌱 Expose handler.MapFunc to allow implementers to test mappers

This is a follow-up from a previous change to the handler package that
deprecated the old handler.ToRequestFunc in favor of
EnqueueRequestsFromMapFunc.

While we still want to prefer using EnqueueRequestsFromMapFunc, this
change also exposes the type of MapFunc signature expected. Users can
use this type to test their own mappers in unit tests.

Signed-off-by: Vince Prignano <vincepri@vmware.com>

pkg/handler/enqueue_mapped.go

@@ -24,6 +24,10 @@ import (
 	"sigs.k8s.io/controller-runtime/pkg/runtime/inject"
 )
 
+// MapFunc is the signature required for enqueueing requests from a generic function.
+// This type is usually used with EnqueueRequestsFromMapFunc when registering an event handler.
+type MapFunc func(MapObject) []reconcile.Request
+
 // EnqueueRequestsFromMapFunc enqueues Requests by running a transformation function that outputs a collection
 // of reconcile.Requests on each Event.  The reconcile.Requests may be for an arbitrary set of objects
 // defined by some user specified transformation of the source Event.  (e.g. trigger Reconciler for a set of objects
@@ -34,17 +38,17 @@ import (
 //
 // For UpdateEvents which contain both a new and old object, the transformation function is run on both
 // objects and both sets of Requests are enqueue.
-func EnqueueRequestsFromMapFunc(mapFN func(MapObject) []reconcile.Request) EventHandler {
+func EnqueueRequestsFromMapFunc(fn MapFunc) EventHandler {
 	return &enqueueRequestsFromMapFunc{
-		ToRequests: toRequestsFunc(mapFN),
+		toRequests: fn,
 	}
 }
 
 var _ EventHandler = &enqueueRequestsFromMapFunc{}
 
 type enqueueRequestsFromMapFunc struct {
 	// Mapper transforms the argument into a slice of keys to be reconciled
-	ToRequests mapper
+	toRequests MapFunc
 }
 
 // Create implements EventHandler
@@ -69,7 +73,7 @@ func (e *enqueueRequestsFromMapFunc) Generic(evt event.GenericEvent, q workqueue
 }
 
 func (e *enqueueRequestsFromMapFunc) mapAndEnqueue(q workqueue.RateLimitingInterface, object MapObject) {
-	for _, req := range e.ToRequests.Map(object) {
+	for _, req := range e.toRequests(object) {
 		q.Add(req)
 	}
 }
@@ -81,26 +85,10 @@ func (e *enqueueRequestsFromMapFunc) InjectFunc(f inject.Func) error {
 	if f == nil {
 		return nil
 	}
-	return f(e.ToRequests)
-}
-
-// mapper maps an object to a collection of keys to be enqueued
-type mapper interface {
-	// Map maps an object
-	Map(MapObject) []reconcile.Request
+	return f(e.toRequests)
 }
 
 // MapObject contains information from an event to be transformed into a Request.
 type MapObject struct {
 	Object controllerutil.Object
 }
-
-var _ mapper = toRequestsFunc(nil)
-
-// toRequestsFunc implements Mapper using a function.
-type toRequestsFunc func(MapObject) []reconcile.Request
-
-// Map implements Mapper
-func (m toRequestsFunc) Map(i MapObject) []reconcile.Request {
-	return m(i)
-}