Do now allow messages to be their own parents in threading

A message may send its own ID in the `references` header. In that case
the threading algorithm must ignore the closed loop and not set the
message as its own parent, to prevent an infinite loop later when
checking for anchestors.

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/IMAP/Threading/ThreadBuilder.php b/lib/IMAP/Threading/ThreadBuilder.php
index 84bcc8cb3..2b3c18f82 100644
--- a/lib/IMAP/Threading/ThreadBuilder.php
+++ b/lib/IMAP/Threading/ThreadBuilder.php
@@ -114,7 +114,7 @@ class ThreadBuilder {
 			// Step 1.C
 			//$parentId = $message->getReferences()[count($message->getReferences()) - 1] ?? null;
 			//$container->setParent($idTable[$parentId] ?? null);
-			if ($parent === null || !$parent->hasAncestor($container)) {
+			if (($parent === null || !$parent->hasAncestor($container)) && $container !== $parent) {
 				$container->setParent($parent);
 			}
 		}