Ignore attempt to empty route spec.host field

pkg/route/registry/route/strategy.go

@@ -60,6 +60,11 @@ func (s routeStrategy) PrepareForUpdate(obj, old runtime.Object) {
 	// Limit to kind/name
 	// TODO: convert to LocalObjectReference
 	route.Spec.To = kapi.ObjectReference{Kind: route.Spec.To.Kind, Name: route.Spec.To.Name}
+	// Ignore attempts to clear the spec Host
+	// Prevents "immutable field" errors when applying the same route definition used to create
+	if len(route.Spec.Host) == 0 {
+		route.Spec.Host = oldRoute.Spec.Host
+	}
 }
 
 // allocateHost allocates a host name ONLY if the host name on the route is empty and an allocator

pkg/route/registry/route/strategy_test.go

@@ -0,0 +1,48 @@
+package route
+
+import (
+	"testing"
+
+	"github.com/openshift/origin/pkg/route/api"
+	kapi "k8s.io/kubernetes/pkg/api"
+	"k8s.io/kubernetes/pkg/types"
+)
+
+type testAllocator struct {
+}
+
+func (t testAllocator) AllocateRouterShard(*api.Route) (*api.RouterShard, error) {
+	return &api.RouterShard{}, nil
+}
+func (t testAllocator) GenerateHostname(*api.Route, *api.RouterShard) string {
+	return "mygeneratedhost.com"
+}
+
+func TestEmptyHostDefaulting(t *testing.T) {
+	strategy := NewStrategy(testAllocator{})
+
+	hostlessCreatedRoute := &api.Route{}
+	strategy.PrepareForCreate(hostlessCreatedRoute)
+	if hostlessCreatedRoute.Spec.Host != "mygeneratedhost.com" {
+		t.Fatalf("Expected host to be allocated, got %s", hostlessCreatedRoute.Spec.Host)
+	}
+
+	persistedRoute := &api.Route{
+		ObjectMeta: kapi.ObjectMeta{
+			Namespace:       "foo",
+			Name:            "myroute",
+			UID:             types.UID("abc"),
+			ResourceVersion: "1",
+		},
+		Spec: api.RouteSpec{
+			Host: "myhost.com",
+		},
+	}
+	obj, _ := kapi.Scheme.DeepCopy(persistedRoute)
+	hostlessUpdatedRoute := obj.(*api.Route)
+	hostlessUpdatedRoute.Spec.Host = ""
+	strategy.PrepareForUpdate(hostlessUpdatedRoute, persistedRoute)
+	if hostlessUpdatedRoute.Spec.Host != "myhost.com" {
+		t.Fatalf("expected empty spec.host to default to existing spec.host, got %s", hostlessUpdatedRoute.Spec.Host)
+	}
+}