flake.py: Add a custom error message for missing clan export

test_clan_create_api: Fix check for SelectCmdError

pkgs/clan-cli/clan_lib/flake/flake.py

@@ -907,6 +907,10 @@ class Flake:
                 ).stdout.strip()
             )
         except ClanCmdError as e:
+            if "error: attribute 'clan' missing" in str(e):
+                msg = ("This flake does not export the 'clan' attribute. \n"
+                    "Please write 'clan = clan.config' into your flake.nix.")
+                raise ClanError(msg) from e
             if "error: attribute" in str(e):
                 # If the error is about a missing attribute, we raise a ClanSelectError
                 # with the failed selectors and the flake identifier.

pkgs/clan-cli/clan_lib/tests/test_create.py

@@ -18,8 +18,8 @@ from clan_cli.vars.generate import get_generators, run_generators
 
 from clan_lib.cmd import RunOpts, run
 from clan_lib.dirs import specific_machine_dir
-from clan_lib.errors import ClanError
-from clan_lib.flake import ClanSelectError, Flake
+from clan_lib.errors import ClanCmdError, ClanError
+from clan_lib.flake import Flake
 from clan_lib.machines.machines import Machine
 from clan_lib.nix import nix_command
 from clan_lib.nix_models.clan import (
@@ -278,10 +278,10 @@ def test_clan_create_api(
 
     if in_sandbox:
         # In sandbox: expect build to fail due to network restrictions
-        with pytest.raises(ClanSelectError) as select_error:
+        with pytest.raises(ClanCmdError) as select_error:
             Path(machine.select("config.system.build.toplevel"))
         # The error should be a select_error without a failed_attr
-        assert select_error.value.failed_attr is None
+        assert "nixos-system-test-clan" in str(select_error.value.cmd.stderr)
     else:
         # Outside sandbox: build should succeed
         toplevel_path = Path(machine.select("config.system.build.toplevel"))