From 3ad22341a27c856a8dd390ef7a036e0007153acf Mon Sep 17 00:00:00 2001
From: Mika Naylor <mail@autophagy.io>
Date: Sat, 24 Dec 2022 14:00:20 +0100
Subject: [PATCH] direnv: enable nushell integration

This enables nushell integration by default for direnv, similar to
bash/zsh/fish. The slightly verbose way of setting this is to ensure
that peoples' existing nushell configuration isn't overwritten, only
appended to, as would be the case if we just used the integration
example from the nushell docs:

  https://www.nushell.sh/cookbook/direnv.html

Closes #3520
---
 modules/programs/direnv.nix               | 25 +++++++++++++++++++++++
 tests/modules/programs/direnv/default.nix |  1 +
 tests/modules/programs/direnv/nushell.nix | 19 +++++++++++++++++
 3 files changed, 45 insertions(+)
 create mode 100644 tests/modules/programs/direnv/nushell.nix

diff --git a/modules/programs/direnv.nix b/modules/programs/direnv.nix
index ad294b2e..1d6ef212 100644
--- a/modules/programs/direnv.nix
+++ b/modules/programs/direnv.nix
@@ -80,6 +80,15 @@ in {
       '';
     };
 
+    enableNushellIntegration = mkOption {
+      default = true;
+      type = types.bool;
+      readOnly = true;
+      description = ''
+        Whether to enable Nushell integration.
+      '';
+    };
+
     nix-direnv = {
       enable = mkEnableOption ''
         <link
@@ -119,5 +128,21 @@ in {
       mkAfter ''
         ${pkgs.direnv}/bin/direnv hook fish | source
       '');
+
+    programs.nushell.extraConfig = mkIf cfg.enableNushellIntegration (
+      # Using mkAfter to make it more likely to appear after other
+      # manipulations of the prompt.
+      mkAfter ''
+        let-env config = ($env | default {} config).config
+        let-env config = ($env.config | default {} hooks)
+        let-env config = ($env.config | update hooks ($env.config.hooks | default [] pre_prompt))
+        let-env config = ($env.config | update hooks.pre_prompt ($env.config.hooks.pre_prompt | append {
+          code: "
+            let direnv = (${pkgs.direnv}/bin/direnv export json | from json)
+            let direnv = if ($direnv | length) == 1 { $direnv } else { {} }
+            $direnv | load-env
+            "
+        }))
+      '');
   };
 }
diff --git a/tests/modules/programs/direnv/default.nix b/tests/modules/programs/direnv/default.nix
index 3efad2b6..a0e61848 100644
--- a/tests/modules/programs/direnv/default.nix
+++ b/tests/modules/programs/direnv/default.nix
@@ -1,6 +1,7 @@
 {
   direnv-bash = ./bash.nix;
   direnv-nix-direnv = ./nix-direnv.nix;
+  direnv-nushell = ./nushell.nix;
   direnv-stdlib = ./stdlib.nix;
   direnv-stdlib-and-nix-direnv = ./stdlib-and-nix-direnv.nix;
 }
diff --git a/tests/modules/programs/direnv/nushell.nix b/tests/modules/programs/direnv/nushell.nix
new file mode 100644
index 00000000..3041770c
--- /dev/null
+++ b/tests/modules/programs/direnv/nushell.nix
@@ -0,0 +1,19 @@
+{ pkgs, ... }:
+
+{
+  programs.nushell.enable = true;
+  programs.direnv.enable = true;
+
+  test.stubs.nushell = { };
+
+  nmt.script = let
+    configFile = if pkgs.stdenv.isDarwin then
+      "home-files/Library/Application Support/nushell/config.nu"
+    else
+      "home-files/.config/nushell/config.nu";
+  in ''
+    assertFileExists "${configFile}"
+    assertFileRegex "${configFile}" \
+      'let direnv = (/nix/store/.*direnv.*/bin/direnv export json | from json)'
+  '';
+}