When downloading with skipVolumeData, keep volume tag

CHANGELOG.unreleased.md

@@ -21,6 +21,7 @@ For upgrade instructions, please check the [migration guide](MIGRATIONS.released
 - Node positions are always handled as integers. They have always been persisted as integers by the server, anyway, but the session in which a node was created handled the position as floating point in earlier versions. [#6589](https://github.com/scalableminds/webknossos/pull/6589)
 - When merging annotations, bounding boxes are no longer duplicated. [#6576](https://github.com/scalableminds/webknossos/pull/6576)
 - Jobs can no longer be started on datastores without workers. [#6595](https://github.com/scalableminds/webknossos/pull/6595)
+- When downloading volume annotations with volume data skipped, the nml volume tag is now included anyway (but has no location attribute in this case). [#6566](https://github.com/scalableminds/webknossos/pull/6566)
 
 ### Fixed
 

app/models/annotation/nml/NmlWriter.scala

@@ -206,21 +206,21 @@ class NmlWriter @Inject()(implicit ec: ExecutionContext) extends FoxImplicits {
                         isSingle: Boolean,
                         volumeFilename: Option[String],
                         skipVolumeData: Boolean)(implicit writer: XMLStreamWriter): Unit =
-    if (skipVolumeData) {
-      writer.writeComment(
-        f"A volume layer named ${volumeLayer.name} (id = $index) was omitted here while downloading this annotation without volume data.")
-    } else {
-      Xml.withinElementSync("volume") {
-        writer.writeAttribute("id", index.toString)
+    Xml.withinElementSync("volume") {
+      writer.writeAttribute("id", index.toString)
+      writer.writeAttribute("name", volumeLayer.name)
+      if (!skipVolumeData) {
         writer.writeAttribute("location", volumeFilename.getOrElse(volumeLayer.volumeDataZipName(index, isSingle)))
-        writer.writeAttribute("name", volumeLayer.name)
-        volumeLayer.tracing match {
-          case Right(volumeTracing) =>
-            volumeTracing.fallbackLayer.foreach(writer.writeAttribute("fallbackLayer", _))
-            volumeTracing.largestSegmentId.foreach(id => writer.writeAttribute("largestSegmentId", id.toString))
-            writeVolumeSegmentMetadata(volumeTracing.segments)
-          case _ => ()
-        }
+      }
+      volumeLayer.tracing match {
+        case Right(volumeTracing) =>
+          volumeTracing.fallbackLayer.foreach(writer.writeAttribute("fallbackLayer", _))
+          volumeTracing.largestSegmentId.foreach(id => writer.writeAttribute("largestSegmentId", id.toString))
+          if (skipVolumeData) {
+            writer.writeComment(f"Note that volume data was omitted when downloading this annotation.")
+          }
+          writeVolumeSegmentMetadata(volumeTracing.segments)
+        case _ => ()
       }
     }