Improve DefinedEntityType.SetBehaviorAccessControls method to avoid N…

…ullPointerException errors (#615)

Signed-off-by: abarreiro <abarreiro@vmware.com>

.changes/v2.22.0/615-improvements.md

@@ -0,0 +1,2 @@
+* Makes `DefinedEntityType` method `SetBehaviorAccessControls` more robust to avoid NullPointerException errors in VCD 
+when the input is a nil slice [GH-615]

govcd/defined_entity.go

@@ -306,6 +306,7 @@ func (rdeType *DefinedEntityType) DeleteBehaviorOverride(behaviorId string) erro
 }
 
 // SetBehaviorAccessControls sets the given slice of BehaviorAccess to the receiver Defined Entity Type.
+// If the input is nil, it removes all access controls from the receiver Defined Entity Type.
 func (det *DefinedEntityType) SetBehaviorAccessControls(acls []*types.BehaviorAccess) error {
 	if det.DefinedEntityType.ID == "" {
 		return fmt.Errorf("ID of the receiver Defined Entity Type is empty")
@@ -322,8 +323,13 @@ func (det *DefinedEntityType) SetBehaviorAccessControls(acls []*types.BehaviorAc
 		return err
 	}
 
+	sanitizedAcls := acls
+	if acls == nil {
+		sanitizedAcls = []*types.BehaviorAccess{}
+	}
+
 	// Wrap it in OpenAPI pages, this endpoint requires it
-	rawMessage, err := json.Marshal(acls)
+	rawMessage, err := json.Marshal(sanitizedAcls)
 	if err != nil {
 		return fmt.Errorf("error setting Access controls in payload: %s", err)
 	}

govcd/defined_entity_test.go

@@ -556,6 +556,17 @@ func testRdeTypeAccessControls(check *C, rdeType *DefinedEntityType, behavior *t
 	err = rdeType.SetBehaviorAccessControls([]*types.BehaviorAccess{})
 	check.Assert(err, IsNil)
 
+	var payload []*types.BehaviorAccess
+	// This one simulates a filtering that goes wrong and leaves "payload" nil
+	for _, acl := range allAccCtrl {
+		if acl.BehaviorId == "notExist" {
+			payload = append(payload, acl)
+		}
+	}
+
+	err = rdeType.SetBehaviorAccessControls(payload) // payload is nil, it should be equivalent to set an empty slice of access controls
+	check.Assert(err, IsNil)
+
 	allAccCtrl, err = rdeType.GetAllBehaviorsAccessControls(nil)
 	check.Assert(err, IsNil)
 	check.Assert(len(allAccCtrl), Equals, 0)