From 54a13b07d5925c8e890e0d9aaa0842cd7ae0d8d6 Mon Sep 17 00:00:00 2001
From: edef <edef@edef.eu>
Date: Sat, 12 Aug 2017 21:14:36 +0200
Subject: [PATCH] switch-to-configuration: use Net::DBus to retrieve the list
 of units

This resolves the FIXME, and opens up the possibility of using more of
the systemd DBus interface to make things more robust.
---
 .../activation/switch-to-configuration.pl     | 19 +++++++++----------
 nixos/modules/system/activation/top-level.nix |  3 ++-
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/nixos/modules/system/activation/switch-to-configuration.pl b/nixos/modules/system/activation/switch-to-configuration.pl
index 87a4ab2a586d..2ce04ed5342c 100644
--- a/nixos/modules/system/activation/switch-to-configuration.pl
+++ b/nixos/modules/system/activation/switch-to-configuration.pl
@@ -4,6 +4,7 @@ use strict;
 use warnings;
 use File::Basename;
 use File::Slurp;
+use Net::DBus;
 use Sys::Syslog qw(:standard :macros);
 use Cwd 'abs_path';
 
@@ -67,17 +68,15 @@ EOF
 $SIG{PIPE} = "IGNORE";
 
 sub getActiveUnits {
-    # FIXME: use D-Bus or whatever to query this, since parsing the
-    # output of list-units is likely to break.
-    # Use current version of systemctl binary before daemon is reexeced.
-    my $lines = `LANG= /run/current-system/sw/bin/systemctl list-units --full --no-legend`;
+    my $mgr = Net::DBus->system->get_service("org.freedesktop.systemd1")->get_object("/org/freedesktop/systemd1");
+    my $units = $mgr->ListUnitsByPatterns([], []);
     my $res = {};
-    foreach my $line (split '\n', $lines) {
-        chomp $line;
-        last if $line eq "";
-        $line =~ /^(\S+)\s+(\S+)\s+(\S+)\s+(\S+)\s/ or next;
-        next if $1 eq "UNIT";
-        $res->{$1} = { load => $2, state => $3, substate => $4 };
+    for my $item (@$units) {
+        my ($id, $description, $load_state, $active_state, $sub_state,
+            $following, $unit_path, $job_id, $job_type, $job_path) = @$item;
+        next unless $following eq '';
+        next if $job_id == 0 and $active_state eq 'inactive';
+        $res->{$id} = { load => $load_state, state => $active_state, substate => $sub_state };
     }
     return $res;
 }
diff --git a/nixos/modules/system/activation/top-level.nix b/nixos/modules/system/activation/top-level.nix
index 091a2e412eed..e2d1dd49ef0e 100644
--- a/nixos/modules/system/activation/top-level.nix
+++ b/nixos/modules/system/activation/top-level.nix
@@ -127,7 +127,8 @@ let
       configurationName = config.boot.loader.grub.configurationName;
 
       # Needed by switch-to-configuration.
-      perl = "${pkgs.perl}/bin/perl -I${pkgs.perlPackages.FileSlurp}/lib/perl5/site_perl";
+
+      perl = "${pkgs.perl}/bin/perl " + (concatMapStringsSep " " (lib: "-I${lib}/${pkgs.perl.libPrefix}") (with pkgs.perlPackages; [ FileSlurp NetDBus XMLParser XMLTwig ]));
   } else throw "\nFailed assertions:\n${concatStringsSep "\n" (map (x: "- ${x}") failed)}");
 
   # Replace runtime dependencies