1 files changed, 36 insertions, 18 deletions

diff --git a/t/thread-cycle.t b/t/thread-cycle.t
index 484ea443..1e5dfb51 100644
--- a/t/thread-cycle.t
+++ b/t/thread-cycle.t
@@ -1,19 +1,16 @@
-# Copyright (C) 2016-2020 all contributors <meta@public-inbox.org>
+# Copyright (C) 2016-2021 all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
-use strict;
-use warnings;
-use Test::More;
-use PublicInbox::TestCommon;
-require_mods 'Email::Simple';
+use strict; use v5.10.1; use PublicInbox::TestCommon;
 use_ok('PublicInbox::SearchThread');
 my $mt = eval {
         require Mail::Thread;
         no warnings 'once';
         $Mail::Thread::nosubject = 1;
         $Mail::Thread::noprune = 1;
+        require Email::Simple; # required by Mail::Thread (via Email::Abstract)
 };
 
-sub make_objs {
+my $make_objs = sub {
         my @simples;
         my $n = 0;
         my @msgs = map {
@@ -21,17 +18,19 @@ sub make_objs {
                 $msg->{ds} ||= ++$n;
                 $msg->{references} =~ s/\s+/ /sg if $msg->{references};
                 $msg->{blob} = '0'x40; # any dummy value will do, here
-                my $simple = Email::Simple->create(header => [
-                        'Message-ID' => "<$msg->{mid}>",
-                        'References' => $msg->{references},
-                ]);
-                push @simples, $simple;
+                if ($mt) {
+                        my $simple = Email::Simple->create(header => [
+                                'Message-ID' => "<$msg->{mid}>",
+                                'References' => $msg->{references},
+                        ]);
+                        push @simples, $simple;
+                }
                 bless $msg, 'PublicInbox::Smsg'
         } @_;
         (\@simples, \@msgs);
-}
+};
 
-my ($simples, $smsgs) = make_objs(
+my ($simples, $smsgs) = $make_objs->(
 # data from t/testbox-6 in Mail::Thread 2.55:
         { mid => '20021124145312.GA1759@nlin.net' },
         { mid => 'slrnau448m.7l4.markj+0111@cloaked.freeserve.co.uk',
@@ -79,13 +78,13 @@ my @backwards = (
         { mid => 8, references => '' }
 );
 
-($simples, $smsgs) = make_objs(@backwards);
+($simples, $smsgs) = $make_objs->(@backwards);
 my $backward = thread_to_s($smsgs);
 SKIP: {
         skip 'Mail::Thread missing', 1 unless $mt;
         check_mt($backward, $simples, 'matches Mail::Thread backwards');
 }
-($simples, $smsgs) = make_objs(reverse @backwards);
+($simples, $smsgs) = $make_objs->(reverse @backwards);
 my $forward = thread_to_s($smsgs);
 unless ('Mail::Thread sorts by Date') {
         SKIP: {
@@ -97,12 +96,31 @@ if ('sorting by Date') {
         is("\n".$backward, "\n".$forward, 'forward and backward matches');
 }
 
-done_testing();
+SKIP: {
+        require_mods 'Devel::Cycle', 1;
+        Devel::Cycle->import('find_cycle');
+        my @dup = (
+                { mid => 5, references => '<6>' },
+                { mid => 5, references => '<6> <1>' },
+        );
+        open my $fh, '+>', \(my $out = '') or xbail "open: $!";
+        (undef, $smsgs) = $make_objs->(@dup);
+        eval 'package EmptyInbox; sub smsg_by_mid { undef }';
+        my $ctx = { ibx => bless {}, 'EmptyInbox' };
+        my $rootset = PublicInbox::SearchThread::thread($smsgs, sub {
+                @{$_[0]} = sort { $a->{mid} cmp $b->{mid} } @{$_[0]} }, $ctx);
+        my $oldout = select $fh;
+        find_cycle($rootset);
+        select $oldout;
+        is($out, '', 'nothing from find_cycle');
+} # Devel::Cycle check
+
+done_testing;
 
 sub thread_to_s {
         my ($msgs) = @_;
         my $rootset = PublicInbox::SearchThread::thread($msgs, sub {
-                [ sort { $a->{mid} cmp $b->{mid} } @{$_[0]} ] });
+                @{$_[0]} = sort { $a->{mid} cmp $b->{mid} } @{$_[0]} });
         my $st = '';
         my @q = map { (0, $_) } @$rootset;
         while (@q) {