From c501a8ff9960252f51979f21a7c2a1e0166f1c2e Mon Sep 17 00:00:00 2001
From: Jan Petykiewicz <jan@mpxd.net>
Date: Mon, 6 Apr 2026 15:30:37 -0700
Subject: [PATCH] [referenced_patterns] don't visit tops twice

---
 masque/library.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/masque/library.py b/masque/library.py
index d7a30af..e98d98d 100644
--- a/masque/library.py
+++ b/masque/library.py
@@ -180,6 +180,8 @@ class ILibraryView(Mapping[str, 'Pattern'], metaclass=ABCMeta):
 
         if isinstance(tops, str):
             tops = (tops,)
+        tops = set(tops)
+        skip |= tops     # don't re-visit tops
 
         # Get referenced patterns for all tops
         targets = set()