Handle http unknown host exception

CHANGELOG.unreleased.md

@@ -19,6 +19,7 @@ For upgrade instructions, please check the [migration guide](MIGRATIONS.released
 - Searching the segments in the sidebar will highlight newly focused segments properly now. [#7406](https://github.com/scalableminds/webknossos/pull/7406)
 - Fixed a bug when opening a task for which a mag restriction exists. The bug only occurred when the referenced mag didn't exist in the dataset. [#7403](https://github.com/scalableminds/webknossos/pull/7403)
 - Fixed styling issues with the maintenance banner so that it no longer overlaps other menus, tabs, and buttons. [#7421](https://github.com/scalableminds/webknossos/pull/7421)
+- Exploring HTTP uris of unknown hosts no longer causes an exception error message to be displayed. [#7422](https://github.com/scalableminds/webknossos/pull/7422)
 
 ### Removed
 

util/src/main/scala/com/scalableminds/util/tools/Fox.scala

@@ -242,6 +242,18 @@ object Fox extends FoxImplicits {
 
     failure.msg + formatStackTrace(failure) + formatChain(failure.chain)
   }
+
+  /**
+    * Transform a Future[T] into a Fox[T] such that if the Future contains an exception, it is turned into a Fox.failure
+    */
+  def transformFuture[T](future: Future[T])(implicit ec: ExecutionContext): Fox[T] =
+    for {
+      fut <- future.transform {
+        case Success(value)        => Try(Fox.successful(value))
+        case scala.util.Failure(e) => Try(Fox.failure(e.getMessage, Full(e)))
+      }
+      f <- fut
+    } yield f
 }
 
 class Fox[+A](val futureBox: Future[Box[A]])(implicit ec: ExecutionContext) {

webknossos-datastore/app/com/scalableminds/webknossos/datastore/datavault/HttpsDataVault.scala

@@ -50,7 +50,7 @@ class HttpsDataVault(credential: Option[DataVaultCredential], ws: WSClient) exte
     headerInfoCache.getOrLoad(
       uri, { uri =>
         for {
-          response <- ws.url(uri.toString).withRequestTimeout(readTimeout).head()
+          response <- Fox.transformFuture(ws.url(uri.toString).withRequestTimeout(readTimeout).head())
           acceptsPartialRequests = response.headerValues("Accept-Ranges").contains("bytes")
           dataSize = response.header("Content-Length").map(_.toLong).getOrElse(0L)
         } yield (acceptsPartialRequests, dataSize)
@@ -60,19 +60,20 @@ class HttpsDataVault(credential: Option[DataVaultCredential], ws: WSClient) exte
   private def getWithRange(uri: URI, range: NumericRange[Long])(implicit ec: ExecutionContext): Fox[WSResponse] =
     for {
       _ <- ensureRangeRequestsSupported(uri)
-      response <- buildRequest(uri).withHttpHeaders("Range" -> s"bytes=${range.start}-${range.end - 1}").get()
+      response <- Fox.transformFuture(
+        buildRequest(uri).withHttpHeaders("Range" -> s"bytes=${range.start}-${range.end - 1}").get())
       _ = updateRangeRequestsSupportedForResponse(response)
     } yield response
 
   private def getWithSuffixRange(uri: URI, length: Long)(implicit ec: ExecutionContext): Fox[WSResponse] =
     for {
       _ <- ensureRangeRequestsSupported(uri)
-      response <- buildRequest(uri).withHttpHeaders("Range" -> s"bytes=-$length").get()
+      response <- Fox.transformFuture(buildRequest(uri).withHttpHeaders("Range" -> s"bytes=-$length").get())
       _ = updateRangeRequestsSupportedForResponse(response)
     } yield response
 
   private def getComplete(uri: URI)(implicit ec: ExecutionContext): Fox[WSResponse] =
-    buildRequest(uri).get()
+    Fox.transformFuture(buildRequest(uri).get())
 
   private def ensureRangeRequestsSupported(uri: URI)(implicit ec: ExecutionContext): Fox[Unit] =
     for {