Update RestoreCSISnapshot function's argument check to fail on zero r…

…estoreSize (#1553)

Signed-off-by: Ivan Sim <ivan.sim@kasten.io>

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

docs/functions.rst

@@ -1414,7 +1414,7 @@ Arguments:
    `pvc`, Yes, `string`, name of the new PVC
    `namespace`, Yes, `string`, namespace of the VolumeSnapshot and resultant PersistentVolumeClaim
    `storageClass`, Yes, `string`, name of the StorageClass
-   `restoreSize`, Yes, `string`, required memory size to restore PVC
+   `restoreSize`, Yes, `string`, required memory size to restore PVC. Must be greater than zero.
    `accessModes`, No, `[]string`, access modes for the underlying PV (Default is ``[]{"ReadWriteOnce"}```)
    `volumeMode`, No, `string`, mode of volume (Default is ``"Filesystem"```)
    `labels`, No, `map[string]string`, optional labels for the PersistentVolumeClaim

pkg/function/restore_csi_snapshot.go

@@ -17,6 +17,7 @@ package function
 import (
 	"context"
 	"errors"
+	"fmt"
 
 	v1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/api/resource"
@@ -113,6 +114,9 @@ func (*restoreCSISnapshotFunc) Exec(ctx context.Context, tp param.TemplateParams
 	if err != nil {
 		return nil, err
 	}
+	if size.IsZero() {
+		return nil, fmt.Errorf("Failed to restore CSI snapshot. restoreSize argument cannot be zero")
+	}
 	restoreArgs.RestoreSize = &size
 
 	kubeCli, err := getClient()