Unify environment configuration and don't run in child shells

This should enable `nix run` to work under shells like fish and zsh,
as well as making child shells not needlessly reset any environment
that should be inherited.

Implementation adapted from NixOS.

4 files changed, 13 insertions, 9 deletions

diff --git a/modules/environment/default.nix b/modules/environment/default.nix
index 6d77cd6..8ba0735 100644
--- a/modules/environment/default.nix
+++ b/modules/environment/default.nix
@@ -184,6 +184,10 @@ in {
     };
 
     system.build.setEnvironment = pkgs.writeText "set-environment" ''
+      # Prevent this file from being sourced by child shells.
+      export __NIX_DARWIN_SET_ENVIRONMENT_DONE=1
+
+      export PATH=${config.environment.systemPath}
       ${concatStringsSep "\n" exportVariables}
 
       # Extra initialisation
diff --git a/modules/programs/bash/default.nix b/modules/programs/bash/default.nix
index ea5afe2..6f5c8e7 100644
--- a/modules/programs/bash/default.nix
+++ b/modules/programs/bash/default.nix
@@ -61,8 +61,9 @@ in
       # Don't execute this file when running in a pure nix-shell.
       if test -n "$IN_NIX_SHELL"; then return; fi
 
-      export PATH=${config.environment.systemPath}
-      ${config.system.build.setEnvironment.text}
+      if [ -z "$__NIX_DARWIN_SET_ENVIRONMENT_DONE" ]; then
+        . ${config.system.build.setEnvironment}
+      fi
 
       # Return early if not running interactively, but after basic nix setup.
       [[ $- != *i* ]] && return
diff --git a/modules/programs/fish.nix b/modules/programs/fish.nix
index 6ee5355..470dcac 100644
--- a/modules/programs/fish.nix
+++ b/modules/programs/fish.nix
@@ -109,8 +109,9 @@ in
       set fish_function_path ${pkgs.fish-foreign-env}/share/fish-foreign-env/functions $__fish_datadir/functions
       
       # source the NixOS environment config
-      fenv export PATH=${config.environment.systemPath}
-      fenv source ${config.system.build.setEnvironment}
+      if [ -z "$__NIX_DARWIN_SET_ENVIRONMENT_DONE" ]
+          fenv source ${config.system.build.setEnvironment}
+      end
 
       # clear fish_function_path so that it will be correctly set when we return to $__fish_datadir/config.fish
       set -e fish_function_path
diff --git a/modules/programs/zsh/default.nix b/modules/programs/zsh/default.nix
index de90433..4d5559a 100644
--- a/modules/programs/zsh/default.nix
+++ b/modules/programs/zsh/default.nix
@@ -120,8 +120,9 @@ in
       # Don't execute this file when running in a pure nix-shell.
       if test -n "$IN_NIX_SHELL"; then return; fi
 
-      export PATH=${config.environment.systemPath}
-      ${config.system.build.setEnvironment.text}
+      if [ -z "$__NIX_DARWIN_SET_ENVIRONMENT_DONE" ]; then
+        . ${config.system.build.setEnvironment}
+      fi
 
       ${cfg.shellInit}
 
@@ -158,9 +159,6 @@ in
       if [ -n "$__ETC_ZSHRC_SOURCED" -o -n "$NOSYSZSHRC" ]; then return; fi
       __ETC_ZSHRC_SOURCED=1
 
-      # Also set to fix `nix run` shells.
-      __ETC_BASHRC_SOURCED=1
-
       # history defaults
       SAVEHIST=2000
       HISTSIZE=2000