Add snapshotClass parameter validation

Validate the snapshotClass parameter in Action.validate(): it must only
appear on snapshot actions, must be a string, and must not be empty.
Follows the same validation pattern as the dataMover parameter.

Ref: #8807

Signed-off-by: Shubham Pampattiwar <spampatt@redhat.com>

internal/resourcepolicies/volume_resources_validator.go

@@ -118,5 +118,19 @@ func (a *Action) validate() error {
 		}
 	}
 
+	if raw, ok := a.Parameters[SnapshotClassParameter]; ok {
+		if a.Type != Snapshot {
+			return fmt.Errorf("parameter %q is only supported for the %q action, but the action type is %q",
+				SnapshotClassParameter, Snapshot, a.Type)
+		}
+		snapshotClass, ok := raw.(string)
+		if !ok {
+			return fmt.Errorf("parameter %q must be a string, got %T", SnapshotClassParameter, raw)
+		}
+		if snapshotClass == "" {
+			return fmt.Errorf("parameter %q must not be empty", SnapshotClassParameter)
+		}
+	}
+
 	return nil
 }

internal/resourcepolicies/volume_resources_validator_test.go

@@ -658,6 +658,86 @@ func TestValidate(t *testing.T) {
 			},
 			wantErr: false,
 		},
+		{
+			name: "snapshot action with valid snapshotClass",
+			res: &ResourcePolicies{
+				Version: "v1",
+				VolumePolicies: []VolumePolicy{
+					{
+						Action: Action{
+							Type:       Snapshot,
+							Parameters: map[string]any{"snapshotClass": "my-vsc"},
+						},
+						Conditions: map[string]any{"storageClass": []string{"gp2"}},
+					},
+				},
+			},
+			wantErr: false,
+		},
+		{
+			name: "snapshot action with both snapshotClass and dataMover",
+			res: &ResourcePolicies{
+				Version: "v1",
+				VolumePolicies: []VolumePolicy{
+					{
+						Action: Action{
+							Type:       Snapshot,
+							Parameters: map[string]any{"snapshotClass": "my-vsc", "dataMover": "velero-fs"},
+						},
+						Conditions: map[string]any{"storageClass": []string{"gp2"}},
+					},
+				},
+			},
+			wantErr: false,
+		},
+		{
+			name: "snapshotClass parameter on non-snapshot action is rejected",
+			res: &ResourcePolicies{
+				Version: "v1",
+				VolumePolicies: []VolumePolicy{
+					{
+						Action: Action{
+							Type:       FSBackup,
+							Parameters: map[string]any{"snapshotClass": "my-vsc"},
+						},
+						Conditions: map[string]any{"storageClass": []string{"gp2"}},
+					},
+				},
+			},
+			wantErr: true,
+		},
+		{
+			name: "snapshot action with non-string snapshotClass is rejected",
+			res: &ResourcePolicies{
+				Version: "v1",
+				VolumePolicies: []VolumePolicy{
+					{
+						Action: Action{
+							Type:       Snapshot,
+							Parameters: map[string]any{"snapshotClass": 123},
+						},
+						Conditions: map[string]any{"storageClass": []string{"gp2"}},
+					},
+				},
+			},
+			wantErr: true,
+		},
+		{
+			name: "snapshot action with empty snapshotClass is rejected",
+			res: &ResourcePolicies{
+				Version: "v1",
+				VolumePolicies: []VolumePolicy{
+					{
+						Action: Action{
+							Type:       Snapshot,
+							Parameters: map[string]any{"snapshotClass": ""},
+						},
+						Conditions: map[string]any{"storageClass": []string{"gp2"}},
+					},
+				},
+			},
+			wantErr: true,
+		},
 	}
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {