issue 6693: partially fail restore if CSI snapshot is involved but CSI feature is not ready

Signed-off-by: Lyndon-Li <lyonghui@vmware.com>

pkg/features/verify.go

@@ -0,0 +1,67 @@
+/*
+Copyright the Velero contributors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package features
+
+import (
+	"errors"
+
+	velerov1api "github.com/vmware-tanzu/velero/pkg/apis/velero/v1"
+	"github.com/vmware-tanzu/velero/pkg/plugin/framework/common"
+)
+
+type PluginFinder interface {
+	Find(kind common.PluginKind, name string) bool
+}
+
+type Verifier struct {
+	finder PluginFinder
+}
+
+func NewVerifier(finder PluginFinder) *Verifier {
+	return &Verifier{
+		finder: finder,
+	}
+}
+
+func (v *Verifier) Verify(name string) (bool, error) {
+	enabled := IsEnabled(name)
+
+	switch name {
+	case velerov1api.CSIFeatureFlag:
+		return verifyCSIFeature(v.finder, enabled)
+	default:
+		return false, nil
+	}
+}
+
+func verifyCSIFeature(finder PluginFinder, enabled bool) (bool, error) {
+	installed := false
+	installed = finder.Find(common.PluginKindBackupItemActionV2, "velero.io/csi-pvc-backupper")
+	if installed {
+		installed = finder.Find(common.PluginKindRestoreItemActionV2, "velero.io/csi-pvc-restorer")
+	}
+
+	if !enabled && installed {
+		return false, errors.New("CSI plugins are registered, but the EnableCSI feature is not enabled")
+	} else if enabled && !installed {
+		return false, errors.New("CSI feature is enabled, but CSI plugins are not registered")
+	} else if !enabled && !installed {
+		return false, nil
+	} else {
+		return true, nil
+	}
+}