[PATCH 3/6] lib: break reference loop by choosing arbitrary top level msg

[David Bremner]

Other parts of notmuch (e.g. notmuch show) expect each thread to
contain at least one top level message, and crash if this expectation
is not met.
---
 lib/thread.cc    | 8 +++++++-
 test/T050-new.sh | 1 -
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/lib/thread.cc b/lib/thread.cc
index 3561b27f..dbac002f 100644
--- a/lib/thread.cc
+++ b/lib/thread.cc
@@ -397,7 +397,13 @@ _resolve_thread_relationships (notmuch_thread_t *thread)
     for (node = thread->message_list->head; node; node = node->next) {
 	message = node->message;
 	in_reply_to = _notmuch_message_get_in_reply_to (message);
-	if (in_reply_to && strlen (in_reply_to) &&
+	/*
+	 * if we reach the end of the list without finding a top-level
+	 * message, that means the thread is a cycle (or set of
+	 * cycles) and any message can be considered top-level
+	 */
+	if ((thread->toplevel_list->head || node->next) &&
+	     in_reply_to && strlen (in_reply_to) &&
 	    g_hash_table_lookup_extended (thread->message_hash,
 					  in_reply_to, NULL,
 					  (void **) &parent))
diff --git a/test/T050-new.sh b/test/T050-new.sh
index b9854978..f3bfe7b1 100755
--- a/test/T050-new.sh
+++ b/test/T050-new.sh
@@ -356,7 +356,6 @@ test_expect_equal_file EXPECTED OUTPUT
 
 add_email_corpus broken
 test_begin_subtest "reference loop does not crash"
-test_subtest_known_broken
 test_expect_code 0 "notmuch show --format=json id:mid-loop-12 at example.org id:mid-loop-21 at example.org > OUTPUT"
 
 test_done
-- 
2.17.0