view: do not prune ghosts from threads

Keeping readers informed of ghost messages is important,
so do not ever prune them.  Previously, ghosts could get
pruned and sole children would get promoted as the new
root.

diff --git a/lib/PublicInbox/View.pm b/lib/PublicInbox/View.pm
index 2cf7e4f01ff120c8c6b4ef3634b944c7f0332043..5f9ecd108aacf444b1ad07a46bfd2b356865ecf8 100644 (file)
--- a/lib/PublicInbox/View.pm
+++ b/lib/PublicInbox/View.pm
@@ -729,8 +729,16 @@ sub thread_results {
        my ($msgs, $nosubject) = @_;
        require PublicInbox::Thread;
        my $th = PublicInbox::Thread->new(@$msgs);
+
+       # WARNING! both these Mail::Thread knobs were found by inspecting
+       # the Mail::Thread 2.55 source code, and we have some monkey patches
+       # in PublicInbox::Thread to fix memory leaks.  Since Mail::Thread
+       # appears unmaintained, I suppose it's safe to depend on these
+       # variables for now:
        no warnings 'once';
        $Mail::Thread::nosubject = $nosubject;
+       # Keep ghosts with only a single direct child:
+       $Mail::Thread::noprune = 1;
        $th->thread;
        $th->order(*sort_ts);
        $th