testing of direnv module for nixpkgs

hosts/gerg-desktop/default.nix

@@ -36,6 +36,12 @@
     "steam"
     "steam-original"
   ];
+  programs.direnv = {
+    enable = true;
+    loadInNixShell = false;
+    silent = true;
+  };
+  programs.fish.enable = true;
 
   nix.settings.system-features = ["kvm" "big-parallel" "nixos-test" "benchmark"];
 

modules/direnv.nix

@@ -1,25 +1,146 @@
-_: {pkgs, ...}: {
+_: {
-  environment = {
+  lib,
-    systemPackages = [pkgs.direnv];
+  config,
-    variables = {
+  pkgs,
-      DIRENV_LOG_FORMAT = "";
+  ...
-      DIRENV_CONFIG = "/etc/direnv";
+}: let
-    };
+  cfg = config.programs.direnv;
-    #other direnv configuration goes here
+in {
-    etc."direnv/direnvrc".text = ''
+  options.programs.direnv = {
-      source ${pkgs.nix-direnv}/share/nix-direnv/direnvrc
+    enable = lib.mkEnableOption (lib.mdDoc ''
+      direnv integration. Takes care of both installation and
+      setting up the sourcing of the shell. Additionally enables nix-direnv
+      integration. Note that you need to logout and login for this change to apply.
+    '');
+
+    package = lib.mkPackageOptionMD pkgs "direnv" {};
+
+    direnvrcExtra = lib.mkOption {
+      type = lib.types.lines;
+      default = "";
+      example = ''
+        export FOO="foo"
+        echo "loaded direnv!"
+      '';
+      description = lib.mdDoc ''
+        Extra lines to append to the sourced direnvrc
       '';
     };
+
+    silent = lib.mkEnableOption (lib.mdDoc ''
+      the hiding of direnv logging
+    '');
+
+    persistDerivations =
+      (lib.mkEnableOption (lib.mdDoc ''
+        setting keep-derivations and keep-outputs to true
+        to prevent shells from getting garbage collected
+      ''))
+      // {
+        default = true;
+      };
+
+    loadInNixShell =
+      lib.mkEnableOption (lib.mdDoc ''
+        loading direnv only outside of `nix-shell` `nix shell` or `nix develop`
+      '')
+      // {
+        default = true;
+      };
+
+    nix-direnv = {
+      enable =
+        (lib.mkEnableOption (lib.mdDoc ''
+          a faster, persistent implementation of use_nix and use_flake, to replace the built-in one
+        ''))
+        // {
+          default = true;
+        };
+
+      package = lib.mkPackageOptionMD pkgs "nix-direnv" {};
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
     programs = {
       zsh.interactiveShellInit = ''
-      if ! printenv PATH | grep -qc '/nix/store' && [ -z "$IN_NIX_SHELL" ] ; then
+        if ${lib.boolToString cfg.loadInNixShell} || printenv PATH | grep -vqc '/nix/store'; then
-        eval "$(direnv hook zsh)"
+         eval "$(${lib.getExe cfg.package} hook zsh)"
         fi
       '';
+
+      #$NIX_GCROOT for "nix develop" https://github.com/NixOS/nix/blob/6db66ebfc55769edd0c6bc70fcbd76246d4d26e0/src/nix/develop.cc#L530
+      #$IN_NIX_SHELL for "nix-shell"
       bash.interactiveShellInit = ''
-      if [[ $- == *i* ]] && ! printenv PATH | grep -qc '/nix/store' && [ -z "$IN_NIX_SHELL" ] ; then
+        if ${lib.boolToString cfg.loadInNixShell} || [ -z "$IN_NIX_SHELL$NIX_GCROOT$(printenv PATH | grep '/nix/store')" ] ; then
-        eval "$(direnv hook bash)"
+         eval "$(${lib.getExe cfg.package} hook bash)"
         fi
       '';
+
+      fish.interactiveShellInit = ''
+        if ${lib.boolToString cfg.loadInNixShell};
+        or printenv PATH | grep -vqc '/nix/store';
+         ${lib.getExe cfg.package} hook fish | source
+        end
+      '';
+    };
+
+    nix.settings = lib.mkIf cfg.persistDerivations {
+      keep-outputs = true;
+      keep-derivations = true;
+    };
+
+    environment = {
+      systemPackages =
+        #direnv has a fish library which sources direnv for some reason
+        if cfg.loadInNixShell
+        then [cfg.package]
+        else [
+          (cfg.package.overrideAttrs (old: {
+            installPhase =
+              (old.installPhase or "")
+              + ''
+                rm -rf $out/share/fish
+              '';
+          }))
+        ];
+
+      variables = {
+        DIRENV_CONFIG = "/etc/direnv";
+        DIRENV_LOG_FORMAT = lib.mkIf cfg.silent "";
+      };
+
+      etc = {
+        "direnv/direnvrc".text = ''
+          ${lib.optionalString cfg.nix-direnv.enable ''
+            #Load nix-direnv
+            source ${cfg.nix-direnv.package}/share/nix-direnv/direnvrc
+          ''}
+
+           #Load direnvrcExtra
+           ${cfg.direnvrcExtra}
+
+           #Load user-configuration if present (~/.direnvrc or ~/.config/direnv/direnvrc)
+           direnv_config_dir_home="''${DIRENV_CONFIG_HOME:-''${XDG_CONFIG_HOME:-$HOME/.config}/direnv}"
+           if [[ -f $direnv_config_dir_home/direnvrc ]]; then
+             source "$direnv_config_dir_home/direnvrc" >&2
+           elif [[ -f $HOME/.direnvrc ]]; then
+             source "$HOME/.direnvrc" >&2
+           fi
+
+           unset direnv_config_dir_home
+        '';
+
+        "direnv/lib/zz-user.sh".text = ''
+          direnv_config_dir_home="''${DIRENV_CONFIG_HOME:-''${XDG_CONFIG_HOME:-$HOME/.config}/direnv}"
+
+          for lib in "$direnv_config_dir_home/lib/"*.sh; do
+            source "$lib"
+          done
+
+          unset direnv_config_dir_home
+        '';
+      };
+    };
   };
 }