From 8fcc9b0e2fddf3a0d9d15330893cb5af19da1538 Mon Sep 17 00:00:00 2001
From: Richard Hansen <rhansen@rhansen.org>
Date: Mon, 29 Jun 2020 00:52:08 -0400
Subject: [PATCH] `group_hosts_by` improvements

  * Don't modify `$config{$h}{$v}` if variable `$v` for host `$h` is
    `undef`.
  * Tolerate the user passing `wantip` or duplicate keys.
---
 ddclient | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/ddclient b/ddclient
index 112acb8..fa2222c 100755
--- a/ddclient
+++ b/ddclient
@@ -2355,13 +2355,11 @@ sub extract_ipv6 {
 ######################################################################
 sub group_hosts_by {
     my ($hosts, $attributes) = @_;
-
+    my %attrs = (map({ ($_ => 1) } @$attributes), 'wantip' => 1);
+    my @attrs = sort(keys(%attrs));
     my %groups = ();
     foreach my $h (@$hosts) {
-        my @keys = (@$attributes, 'wantip');
-        map { $config{$h}{$_} = '' unless exists $config{$h}{$_} } @keys;
-        my $sig = join(',', map { "$_=$config{$h}{$_}" } @keys);
-
+        my $sig = join(',', map({ sprintf("%s=%s", $_, $config{$h}{$_} // '') } @attrs));
         push @{$groups{$sig}}, $h;
     }
     return %groups;