Hide system actor from user list and block show/edit

Index: filter out SystemActor.system_user_email() in query. Show/Form:
redirect to /users with flash when viewing or editing system actor user.
Index format_error: handle Ash errors without :message field.

lib/mv_web/live/user_live/form.ex

@@ -266,10 +266,31 @@ defmodule MvWeb.UserLive.Form do
 
     user =
       case params["id"] do
-        nil -> nil
-        id -> Ash.get!(Mv.Accounts.User, id, domain: Mv.Accounts, load: [:member], actor: actor)
+        nil ->
+          nil
+
+        id ->
+          loaded =
+            Ash.get!(Mv.Accounts.User, id, domain: Mv.Accounts, load: [:member], actor: actor)
+
+          if to_string(loaded.email) == Mv.Helpers.SystemActor.system_user_email() do
+            {:redirect, loaded}
+          else
+            loaded
+          end
       end
 
+    if match?({:redirect, _}, user) do
+      {:ok,
+       socket
+       |> put_flash(:error, gettext("This user cannot be edited."))
+       |> push_navigate(to: ~p"/users")}
+    else
+      mount_continue(user, params, socket)
+    end
+  end
+
+  defp mount_continue(user, params, socket) do
     action = if is_nil(user), do: gettext("New"), else: gettext("Edit")
     page_title = action <> " " <> gettext("User")
 

lib/mv_web/live/user_live/index.ex

@@ -25,10 +25,17 @@ defmodule MvWeb.UserLive.Index do
 
   import MvWeb.LiveHelpers, only: [current_actor: 1]
 
+  require Ash.Query
+
   @impl true
   def mount(_params, _session, socket) do
     actor = current_actor(socket)
-    users = Ash.read!(Mv.Accounts.User, domain: Mv.Accounts, load: [:member], actor: actor)
+
+    users =
+      Mv.Accounts.User
+      |> Ash.Query.filter(email != ^Mv.Helpers.SystemActor.system_user_email())
+      |> Ash.read!(domain: Mv.Accounts, load: [:member], actor: actor)
+
     sorted = Enum.sort_by(users, & &1.email)
 
     {:ok,
@@ -138,8 +145,11 @@ defmodule MvWeb.UserLive.Index do
   defp sort_fun(:asc), do: &<=/2
   defp sort_fun(:desc), do: &>=/2
 
-  defp format_error(%Ash.Error.Invalid{errors: errors}) do
-    Enum.map_join(errors, ", ", fn %{message: message} -> message end)
+  defp format_error(%Ash.Error.Invalid{errors: errors}) when is_list(errors) do
+    Enum.map_join(errors, ", ", fn
+      %{message: message} when is_binary(message) -> message
+      other -> inspect(other)
+    end)
   end
 
   defp format_error(error) do

lib/mv_web/live/user_live/show.ex

@@ -75,9 +75,16 @@ defmodule MvWeb.UserLive.Show do
     actor = current_actor(socket)
     user = Ash.get!(Mv.Accounts.User, id, domain: Mv.Accounts, load: [:member], actor: actor)
 
+    if to_string(user.email) == Mv.Helpers.SystemActor.system_user_email() do
+      {:ok,
+       socket
+       |> put_flash(:error, gettext("This user cannot be viewed."))
+       |> push_navigate(to: ~p"/users")}
+    else
       {:ok,
        socket
        |> assign(:page_title, gettext("Show User"))
        |> assign(:user, user)}
     end
+  end
 end