From 59296fbbc36a51892dbe03f5663ee92de20dd494 Mon Sep 17 00:00:00 2001
From: Vladimir Pouzanov <farcaller@gmail.com>
Date: Thu, 19 Jan 2023 16:28:54 +0000
Subject: [PATCH 1/2] Assert that fish configuration is enabled if any user has
 fish as their shell.

Suggested-By: matthiasbeyer
---
 nixos/modules/config/users-groups.nix | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/nixos/modules/config/users-groups.nix b/nixos/modules/config/users-groups.nix
index 76092e738eb..a727f8510f8 100644
--- 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;
+            '';
+          }
         ]
     ));
 

From 631b7f6f882b05c2a5c35f088bfdd99ebbcbf1f3 Mon Sep 17 00:00:00 2001
From: Vladimir Pouzanov <farcaller@gmail.com>
Date: Thu, 19 Jan 2023 16:59:11 +0000
Subject: [PATCH 2/2] Add support for the other shells

---
 nixos/modules/config/users-groups.nix | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/nixos/modules/config/users-groups.nix b/nixos/modules/config/users-groups.nix
index a727f8510f8..91d6c9026d8 100644
--- a/nixos/modules/config/users-groups.nix
+++ b/nixos/modules/config/users-groups.nix
@@ -693,17 +693,20 @@ in {
               users.groups.${user.name} = {};
             '';
           }
-          {
-            assertion = (user.shell == pkgs.fish) -> (config.programs.fish.enable == true);
+        ] ++ (map (shell: {
+            assertion = (user.shell == pkgs.${shell}) -> (config.programs.${shell}.enable == true);
             message = ''
-              users.users.${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
+              users.users.${user.name}.shell is set to ${shell}, but
+              programs.${shell}.enable is not true. This will cause the ${shell}
+              shell to lack the basic nix directories in its PATH and might make
               logging in as that user impossible. You can fix it with:
-              programs.fish.enable = true;
+              programs.${shell}.enable = true;
             '';
-          }
-        ]
+          }) [
+          "fish"
+          "xonsh"
+          "zsh"
+        ])
     ));
 
     warnings =