update to disallow update once external strategy type

Signed-off-by: Britania Rodriguez Reyes <[email protected]>

Author: britaniar

config/crd/bases/placement.kubernetes-fleet.io_clusterresourceplacements.yaml

@@ -2483,8 +2483,9 @@ spec:
                     - External
                     type: string
                     x-kubernetes-validations:
-                    - message: rollout strategy type is immutable
-                      rule: '!(self != oldSelf)'
+                    - message: cannot change rollout strategy type from 'External'
+                        to other types
+                      rule: '!(self != ''External'' && oldSelf == ''External'')'
                 type: object
             required:
             - resourceSelectors

config/crd/bases/placement.kubernetes-fleet.io_resourceplacements.yaml

@@ -993,8 +993,9 @@ spec:
                     - External
                     type: string
                     x-kubernetes-validations:
-                    - message: rollout strategy type is immutable
-                      rule: '!(self != oldSelf)'
+                    - message: cannot change rollout strategy type from 'External'
+                        to other types
+                      rule: '!(self != ''External'' && oldSelf == ''External'')'
                 type: object
             required:
             - resourceSelectors

test/apis/placement/v1beta1/api_validation_integration_test.go

@@ -142,6 +142,9 @@ var _ = Describe("Test placement v1beta1 API validation", func() {
 						PlacementType: placementv1beta1.PickFixedPlacementType,
 						ClusterNames:  []string{"cluster1", "cluster2"},
 					},
+					Strategy: placementv1beta1.RolloutStrategy{
+						Type: placementv1beta1.ExternalRolloutStrategyType,
+					},
 				},
 			}
 			Expect(hubClient.Create(ctx, &crp)).Should(Succeed())
@@ -167,13 +170,12 @@ var _ = Describe("Test placement v1beta1 API validation", func() {
 			Expect(statusErr.ErrStatus.Message).Should(MatchRegexp("placement type is immutable"))
 		})
 
-		It("should deny update of RolloutStrategy type", func() {
-			// Default RolloutStrategy type is RollingUpdate
-			crp.Spec.Strategy.Type = placementv1beta1.ExternalRolloutStrategyType
+		It("should deny update of RolloutStrategy type when External", func() {
+			crp.Spec.Strategy.Type = placementv1beta1.RollingUpdateRolloutStrategyType
 			err := hubClient.Update(ctx, &crp)
 			var statusErr *k8sErrors.StatusError
 			Expect(errors.As(err, &statusErr)).To(BeTrue(), fmt.Sprintf("Update CRP call produced error %s. Error type wanted is %s.", reflect.TypeOf(err), reflect.TypeOf(&k8sErrors.StatusError{})))
-			Expect(statusErr.ErrStatus.Message).Should(MatchRegexp("rollout strategy type is immutable"))
+			Expect(statusErr.ErrStatus.Message).Should(MatchRegexp("cannot change rollout strategy type from 'External' to other types"))
 		})
 	})