direnv: add nix-direnv to lib instead of sourcing

Also removes use of `with lib`.

modules/programs/direnv.nix

@@ -1,8 +1,8 @@
 { config, lib, pkgs, ... }:
-
-with lib;
-
 let
+  inherit (lib)
+    mkOption mkRenamedOptionModule mkRemovedOptionModule mkEnableOption types
+    mkPackageOption mkIf mkAfter getExe;
 
   cfg = config.programs.direnv;
 
@@ -19,7 +19,7 @@ in {
       "Flake support is now always enabled.")
   ];
 
-  meta.maintainers = [ maintainers.rycee ];
+  meta.maintainers = [ lib.maintainers.rycee ];
 
   options.programs.direnv = {
     enable = mkEnableOption "direnv, the environment switcher";
@@ -104,11 +104,12 @@ in {
       source = tomlFormat.generate "direnv-config" cfg.config;
     };
 
-    xdg.configFile."direnv/direnvrc" = let
-      text = concatStringsSep "\n" (optional (cfg.stdlib != "") cfg.stdlib
-        ++ optional cfg.nix-direnv.enable
-        "source ${cfg.nix-direnv.package}/share/nix-direnv/direnvrc");
-    in mkIf (text != "") { inherit text; };
+    xdg.configFile."direnv/lib/hm-nix-direnv.sh" = mkIf cfg.nix-direnv.enable {
+      source = "${cfg.nix-direnv.package}/share/nix-direnv/direnvrc";
+    };
+
+    xdg.configFile."direnv/direnvrc" =
+      lib.mkIf (cfg.stdlib != "") { text = cfg.stdlib; };
 
     programs.bash.initExtra = mkIf cfg.enableBashIntegration (
       # Using mkAfter to make it more likely to appear after other

tests/modules/programs/direnv/nix-direnv.nix

@@ -10,9 +10,7 @@ with lib;
 
     nmt.script = ''
       assertFileExists home-files/.bashrc
-      assertFileRegex \
-        home-files/.config/direnv/direnvrc \
-        'source /nix/store/.*nix-direnv.*/share/nix-direnv/direnvrc'
+      assertFileExists home-files/.config/direnv/lib/hm-nix-direnv.sh
     '';
   };
 }

tests/modules/programs/direnv/stdlib-and-nix-direnv.nix

@@ -12,9 +12,7 @@ in {
 
     nmt.script = ''
       assertFileExists home-files/.bashrc
-      assertFileRegex \
-        home-files/.config/direnv/direnvrc \
-        'source /nix/store/.*nix-direnv.*/share/nix-direnv/direnvrc'
+      assertFileExists home-files/.config/direnv/lib/hm-nix-direnv.sh
       assertFileRegex \
         home-files/.config/direnv/direnvrc \
         '${expectedContent}'

tests/modules/programs/direnv/stdlib.nix

@@ -10,6 +10,7 @@ in {
     programs.direnv.stdlib = expectedContent;
 
     nmt.script = ''
+      assertPathNotExists home-files/.config/direnv/lib/hm-nix-direnv.sh
       assertFileExists home-files/.bashrc
       assertFileRegex \
         home-files/.config/direnv/direnvrc \