Assert that fish configuration is enabled if any user has fish as their shell.

farcaller · farcaller · commit 59296fbbc36a · 2023-01-19T16:28:54.000Z
Suggested-By: matthiasbeyer
diff --git a/nixos/modules/config/users-groups.nix b/nixos/modules/config/users-groups.nix
@@ -693,6 +693,16 @@ in {
               users.groups.${user.name} = {};
             '';
           }
+          {
+            assertion = (user.shell == pkgs.fish) -> (config.programs.fish.enable == true);
+            message = ''
+              users.users.${user.name}.shell is set to fish, but
+              programs.fish.enable is not true. This will cause the fish shell
+              to lack the basic nix directories in its PATH and might make
+              logging in as that user impossible. You can fix it with:
+              programs.fish.enable = true;
+            '';
+          }
         ]
     ));
 
