Allow kubernetes apiVersion upgrades

Use the API version of the desired state to get current state
and then determine the patch from there

Author: willthames

kustomize/resource_kustomization.go

@@ -190,12 +190,12 @@ func kustomizationResourceDiff(d *schema.ResourceDiff, m interface{}) error {
 		return nil
 	}
 
-	srcJSON := originalJSON.(string)
-	if srcJSON == "" {
+	desiredJSON := modifiedJSON.(string)
+	if desiredJSON == "" {
 		return nil
 	}
 
-	u, err := parseJSON(srcJSON)
+	u, err := parseJSON(desiredJSON)
 	if err != nil {
 		return logError(fmt.Errorf("JSON parse error: %s", err))
 	}

kustomize/util.go

@@ -50,7 +50,7 @@ func getOriginalModifiedCurrent(originalJSON string, modifiedJSON string, curren
 	setLastAppliedConfig(o, originalJSON)
 	setLastAppliedConfig(n, modifiedJSON)
 
-	mapping, err := mapper.RESTMapping(o.GroupVersionKind().GroupKind(), o.GroupVersionKind().Version)
+	mapping, err := mapper.RESTMapping(n.GroupVersionKind().GroupKind(), n.GroupVersionKind().Version)
 	if err != nil {
 		return nil, nil, nil, err
 	}
@@ -94,7 +94,6 @@ func getPatch(gvk k8sschema.GroupVersionKind, original []byte, modified []byte,
 		patchType = k8stypes.MergePatchType
 
 		preconditions := []mergepatch.PreconditionFunc{
-			mergepatch.RequireKeyUnchanged("apiVersion"),
 			mergepatch.RequireKeyUnchanged("kind"),
 			mergepatch.RequireMetadataKeyUnchanged("name"),
 		}