fish: expose session variables package

This allows fish users to source the `hm-session-vars.fish` if they are
not using the generated `config.fish` (which now sources the same file).

docs/manual/faq/session-variables.md

@@ -17,8 +17,11 @@ way. In Bash and Z shell this can be done by adding
 to your `.profile` and `.zshrc` files, respectively. The
 `hm-session-vars.sh` file should work in most Bourne-like shells. For
 fish shell, it is possible to source it using [the foreign-env
-plugin](https://github.com/oh-my-fish/plugin-foreign-env)
+plugin](https://github.com/oh-my-fish/plugin-foreign-env) or using the builtin
+[babelfish](https://github.com/bouk/babelfish)-translated variables:
 
 ``` bash
 fenv source "$HOME/.nix-profile/etc/profile.d/hm-session-vars.sh" > /dev/null
+# or
+source "$HOME/.nix-profile/etc/profile.d/hm-session-vars.fish"
 ```

modules/programs/fish.nix

@@ -220,13 +220,16 @@ let
       passAsFile = [ "text" ];
     } "env HOME=$(mktemp -d) fish_indent < $textPath > $out";
 
+  profileDir = "/etc/profile.d";
+  translatedSessionVarsFile = "hm-session-vars.fish";
   translatedSessionVariables =
-    pkgs.runCommandLocal "hm-session-vars.fish" { } ''
+    pkgs.runCommandLocal translatedSessionVarsFile { } ''
+      mkdir -p $out/${profileDir}
       (echo "function setup_hm_session_vars;"
       ${pkgs.buildPackages.babelfish}/bin/babelfish \
         <${config.home.sessionVariablesPackage}/etc/profile.d/hm-session-vars.sh
       echo "end"
-      echo "setup_hm_session_vars") > $out
+      echo "setup_hm_session_vars") > $out/${profileDir}/${translatedSessionVarsFile}
     '';
 
 in {
@@ -393,11 +396,24 @@ in {
         <https://fishshell.com/docs/current/cmds/function.html>.
       '';
     };
+
+    # TODO: maybe this makes more sense as `programs.fish.sessionVariablesPackage`?
+    # if `programs.fish.sessionVariables` were added, would that need its own
+    # separate package, or would they just go in config.fish directly?
+    home.fishSessionVariablesPackage = mkOption {
+      type = types.package;
+      internal = true;
+      description = ''
+        The package containing the translated {file}`hm-session-vars.fish` file.
+      '';
+    };
   };
 
   config = mkIf cfg.enable (mkMerge [
-    { home.packages = [ cfg.package ]; }
-
+    {
+      home.fishSessionVariablesPackage = translatedSessionVariables;
+      home.packages = [ cfg.package config.home.fishSessionVariablesPackage ];
+    }
     (mkIf cfg.generateCompletions {
       # Support completion for `man` by building a cache for `apropos`.
       programs.man.generateCaches = mkDefault true;
@@ -473,7 +489,7 @@ in {
         set -q __fish_home_manager_config_sourced; and exit
         set -g __fish_home_manager_config_sourced 1
 
-        source ${translatedSessionVariables}
+        source ${config.home.fishSessionVariablesPackage}/${profileDir}/${translatedSessionVarsFile}
 
         ${cfg.shellInit}
 

tests/modules/programs/fish/default.nix

@@ -4,4 +4,5 @@
   fish-functions = ./functions.nix;
   fish-no-functions = ./no-functions.nix;
   fish-plugins = ./plugins.nix;
+  fish-session-variables = ./session-variables.nix;
 }

tests/modules/programs/fish/session-variables.nix

@@ -0,0 +1,26 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+{
+  config = {
+    home.sessionVariables = {
+      V1 = "v1";
+      V2 = "v2-${config.home.sessionVariables.V1}";
+    };
+
+    programs.fish = {
+      enable = true;
+
+      # TODO: should there be an equivalent sessionVariables here like bash + zsh?
+    };
+
+    nmt.script = ''
+      assertFileExists home-path/etc/profile.d/hm-session-vars.fish
+      assertFileRegex home-path/etc/profile.d/hm-session-vars.fish \
+        "set -gx V1 'v1'"
+      assertFileRegex home-path/etc/profile.d/hm-session-vars.fish \
+        "set -gx V1 'v1'"
+    '';
+  };
+}