Install direnv.

nix/configuration/roles/direnv/default.nix

@@ -0,0 +1,55 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+
+let
+  direnv_zsh_hook = pkgs.writeTextFile {
+    name = "direnv_zsh_hook.zsh";
+    text = ''
+      eval "$(direnv hook zsh)"
+    '';
+  };
+in
+{
+  imports = [ ];
+
+  options.me = {
+    direnv.enable = lib.mkOption {
+      type = lib.types.bool;
+      default = false;
+      example = true;
+      description = "Whether we want to install direnv.";
+    };
+  };
+
+  config = lib.mkIf config.me.direnv.enable (
+    lib.mkMerge [
+      {
+        environment.systemPackages = with pkgs; [
+          direnv
+          nix-direnv
+        ];
+
+        me.zsh.includes = [ direnv_zsh_hook ];
+
+        environment.persistence."/persist" = lib.mkIf (!config.me.buildingIso) {
+          hideMounts = true;
+          users.talexander = {
+            directories = [
+              {
+                # List of allowed directories from `direnv allow`.
+                directory = ".local/share/direnv";
+                user = "talexander";
+                group = "talexander";
+                mode = "0755";
+              }
+            ];
+          };
+        };
+      }
+    ]
+  );
+}

nix/configuration/roles/zsh/default.nix

@@ -49,6 +49,8 @@ let
 
       source ${pkgs.zsh-histdb}/share/zsh/plugins/zsh-histdb/histdb-interactive.zsh
       bindkey '^r' _histdb-isearch
+
+      ${lib.concatMapStringsSep "\n" (item: "source ${item}") config.me.zsh.includes}
     '';
   };
 in
@@ -62,6 +64,16 @@ in
       example = true;
       description = "Whether we want to install zsh.";
     };
+    zsh.includes = lib.mkOption {
+      type = lib.types.listOf lib.types.package;
+      default = [ ];
+      example = lib.literalExpression ''
+        [ (pkgs.writeTextFile {
+            name = "launch-kanshi.conf";
+            text = "exec kanshi";
+          }) ]'';
+      description = "List of zshrc files to import.";
+    };
   };
 
   config = lib.mkIf config.me.zsh.enable (