nixos/zfs: assert that pool names are not empty

a zfs fileSystems entry with an absolute (e.g. device) path rather than
a zfs dataser is parsed as an empty pool name, causing a doomed-to-fail
import job to be created as a boot dependency. Catch this as an assertion

1 files changed, 9 insertions, 0 deletions

diff --git a/nixos/modules/tasks/filesystems/zfs.nix b/nixos/modules/tasks/filesystems/zfs.nix
index 16dc0c44c18..c214e277db4 100644
--- a/nixos/modules/tasks/filesystems/zfs.nix
+++ b/nixos/modules/tasks/filesystems/zfs.nix
@@ -523,6 +523,15 @@ in
           assertion = cfgZfs.allowHibernation -> !cfgZfs.forceImportRoot && !cfgZfs.forceImportAll;
           message = "boot.zfs.allowHibernation while force importing is enabled will cause data corruption";
         }
+        {
+          assertion = !(elem "" allPools);
+          message = ''
+            Automatic pool detection found an empty pool name, which can't be used.
+            Hint: for `fileSystems` entries with `fsType = zfs`, the `device` attribute
+            should be a zfs dataset name, like `device = "pool/data/set"`.
+            This error can be triggered by using an absolute path, such as `"/dev/disks/..."`.
+          '';
+        }
       ];
 
       boot = {