nushell: load session environment at runtime

docs/release-notes/rl-2611.md

@@ -20,6 +20,13 @@ This release has the following notable changes:
   domain to `user` for agents that should run without an active graphical login
   session.
 
+- [](#opt-programs.nushell.enable) now loads [](#opt-home.sessionVariables)
+  when Nushell starts directly. When Home Manager is used as a NixOS or
+  nix-darwin module, it also loads the system environment. This makes its
+  environment consistent with managed Bash and Zsh sessions. If you manage
+  Nushell's `env.nu` independently, migrate its contents to
+  [](#opt-programs.nushell.envFile) or [](#opt-programs.nushell.extraEnv).
+
 ## State Version Changes {#sec-release-26.11-state-version-changes}
 
 The state version in this release includes the changes below. These

modules/programs/nushell.nix

@@ -1,6 +1,7 @@
 {
   config,
   lib,
+  osConfig,
   pkgs,
   ...
 }:
@@ -9,6 +10,102 @@ let
   inherit (lib.hm.nushell) isNushellInline toNushell;
   cfg = config.programs.nushell;
 
+  systemEnvironmentPath = [
+    "system"
+    "build"
+    "setEnvironment"
+  ];
+  effectiveOsConfig = if osConfig == null then { } else osConfig;
+  getSystemEnvironment = lib.attrByPath systemEnvironmentPath null;
+  systemEnvironmentFile = getSystemEnvironment effectiveOsConfig;
+  hasSystemEnvironment = systemEnvironmentFile != null;
+  sessionVariablesPackage = toString config.home.sessionVariablesPackage;
+  sessionVariablesFile = "/etc/profile.d/hm-session-vars.sh";
+  homeSessionVariablesFile = sessionVariablesPackage + sessionVariablesFile;
+  hasSessionEnvironment =
+    systemEnvironmentFile != null
+    || config.home.sessionVariables != { }
+    || config.home.sessionSearchVariables != { }
+    || config.home.sessionVariablesExtra != "";
+  hasUserEnvFile = cfg.envFile != null || cfg.extraEnv != "";
+  writeEnvFile = hasSessionEnvironment || hasUserEnvFile;
+
+  # Translate the POSIX session scripts at shell startup so references to
+  # runtime values such as HOME and USER are expanded in the user environment.
+  sessionVariablesLoader =
+    let
+      sourceSystemEnvironment = lib.optionalString hasSystemEnvironment ''
+        if [ -z "''${__NIXOS_SET_ENVIRONMENT_DONE-}" ] \
+          && [ -z "''${__NIX_DARWIN_SET_ENVIRONMENT_DONE-}" ]; then
+          . ${lib.escapeShellArg systemEnvironmentFile} >/dev/null
+        fi
+      '';
+      captureEnvironment = ''
+        ${lib.getExe' pkgs.coreutils "env"} -0
+        printf '\0'
+        ${sourceSystemEnvironment}
+        . ${lib.escapeShellArg homeSessionVariablesFile} >/dev/null
+        ${lib.getExe' pkgs.coreutils "env"} -0
+      '';
+      shouldLoadSystemEnvironment = lib.optionalString hasSystemEnvironment ''
+        or (
+          "__NIXOS_SET_ENVIRONMENT_DONE" not-in $env
+          and "__NIX_DARWIN_SET_ENVIRONMENT_DONE" not-in $env
+        )
+      '';
+    in
+    pkgs.writeText "hm-session-vars.nu" ''
+      if (
+        "__HM_SESS_VARS_SOURCED" not-in $env
+        ${shouldLoadSystemEnvironment}
+      ) {
+        let captured = (
+          ^${pkgs.runtimeShell} -c ${toNushell { } captureEnvironment}
+          | complete
+        )
+
+        if $captured.exit_code != 0 {
+          error make {
+            msg: "failed to load the Home Manager session environment"
+            help: $captured.stderr
+          }
+        }
+
+        let separator = $"(char nul)(char nul)"
+        let sections = ($captured.stdout | split row $separator)
+
+        if ($sections | length) != 2 {
+          error make {
+            msg: "failed to parse the Home Manager session environment"
+          }
+        }
+
+        let before = (
+          $sections
+          | first
+          | split row (char nul)
+          | compact --empty
+        )
+        let changed = (
+          $sections
+          | last
+          | split row (char nul)
+          | compact --empty
+          | where { |entry| $entry not-in $before }
+          | parse --regex '(?s)^(?<name>[^=]+)=(?<value>.*)$'
+          | where { |entry| $entry.name not-in ["_" "_AST_FEATURES" "SHLVL"] }
+          | transpose --header-row --as-record
+        )
+        let changed = if "PATH" in $changed {
+          $changed | update PATH ($changed.PATH | split row (char esep))
+        } else {
+          $changed
+        }
+
+        load-env $changed
+      }
+    '';
+
   linesOrSource =
     name:
     types.submodule (
@@ -279,8 +376,9 @@ in
         }
       )
 
-      (lib.mkIf (cfg.envFile != null || cfg.extraEnv != "") {
+      (lib.mkIf writeEnvFile {
         "${cfg.configDir}/env.nu".text = lib.mkMerge [
+          (lib.mkIf hasSessionEnvironment "source ${sessionVariablesLoader}")
           (lib.mkIf (cfg.envFile != null) cfg.envFile.text)
           cfg.extraEnv
         ];

tests/modules/programs/nushell/default.nix

@@ -1,4 +1,5 @@
 {
   nushell-example-settings = ./example-settings.nix;
   nushell-config-dir = ./config-dir.nix;
+  nushell-session-variables = ./session-variables.nix;
 }

tests/modules/programs/nushell/env-expected.nu

@@ -1,2 +1,2 @@
+source /nix/store/00000000000000000000000000000000-hm-session-vars.nu
 $env.FOO = 'BAR'
-

tests/modules/programs/nushell/example-settings.nix

@@ -19,9 +19,7 @@
       }
     '';
 
-    envFile.text = ''
-      $env.FOO = 'BAR'
-    '';
+    envFile.text = "$env.FOO = 'BAR'";
 
     loginFile.text = ''
       # Prints "Hello, World" upon logging into tty1
@@ -75,7 +73,7 @@
         "${configDir}/config.nu" \
         ${./config-expected.nu}
       assertFileContent \
-        "${configDir}/env.nu" \
+        "$(normalizeStorePaths "${configDir}/env.nu")" \
         ${./env-expected.nu}
       assertFileContent \
         "${configDir}/login.nu" \

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

@@ -0,0 +1,80 @@
+{
+  config,
+  lib,
+  pkgs,
+  realPkgs,
+  ...
+}:
+
+let
+  systemEnvironment = realPkgs.writeText "set-environment" ''
+    export __NIXOS_SET_ENVIRONMENT_DONE=1
+    export SYSTEM_VALUE="$HOME/$USER"
+    export PATH="/system/bin:$PATH"
+  '';
+  expected = pkgs.writeText "expected-session-variables" ''
+    /runtime/home/runtime-user
+    /runtime/home/.config
+    fallback
+    home-is-set
+    /runtime/home/.local/bin:/system/bin
+    env-file-loaded
+  '';
+in
+{
+  _module.args.osConfig.system.build.setEnvironment = systemEnvironment;
+
+  nixpkgs.overlays = [
+    (_final: _prev: { runtimeShell = "/bin/sh"; })
+  ];
+
+  home = {
+    sessionPath = [ "$HOME/.local/bin" ];
+    sessionVariables = {
+      ALTERNATE_VALUE = "\${HOME:+home-is-set}";
+      DEFAULT_VALUE = "\${UNSET_VARIABLE:-fallback}";
+      EXPANDED_HOME = "$HOME/.config";
+    };
+  };
+
+  programs.nushell = {
+    enable = true;
+    package = realPkgs.nushell;
+    envFile.text = ''
+      $env.USER_ENV_FILE = "env-file-loaded"
+    '';
+  };
+
+  nmt.script =
+    let
+      homePrefix = "${config.home.homeDirectory}/";
+      configDir = lib.removePrefix homePrefix config.programs.nushell.configDir;
+      envFile = "home-files/${configDir}/env.nu";
+    in
+    ''
+      assertFileRegex ${envFile} \
+        '^source /nix/store/[^/]*-hm-session-vars.nu$'
+
+      actual="$PWD/actual"
+      env -i \
+        HOME=/runtime/home \
+        USER=runtime-user \
+        PATH=/initial/bin \
+        ${lib.getExe realPkgs.nushell} \
+          --no-history \
+          --config /dev/null \
+          --env-config "$(_abs ${envFile})" \
+          --commands '
+            print ([
+              $env.SYSTEM_VALUE
+              $env.EXPANDED_HOME
+              $env.DEFAULT_VALUE
+              $env.ALTERNATE_VALUE
+              ($env.PATH | first 2 | str join (char esep))
+              $env.USER_ENV_FILE
+            ] | str join (char newline))
+          ' > "$actual"
+
+      assertFileContent "$actual" ${expected}
+    '';
+}