[ILibraryView] don't fail on nested dangling ref

masque/test/test_library.py

@@ -166,6 +166,24 @@ def test_library_flatten_repeated_ref_with_ports_raises() -> None:
         lib.flatten("parent", flatten_ports=True)
 
 
+def test_library_flatten_dangling_ok_nested_preserves_dangling_refs() -> None:
+    lib = Library()
+    child = Pattern()
+    child.ref("missing")
+    lib["child"] = child
+
+    parent = Pattern()
+    parent.ref("child")
+    lib["parent"] = parent
+
+    flat = lib.flatten("parent", dangling_ok=True)
+
+    assert set(flat["child"].refs) == {"missing"}
+    assert flat["child"].has_refs()
+    assert set(flat["parent"].refs) == {"missing"}
+    assert flat["parent"].has_refs()
+
+
 def test_lazy_library() -> None:
     lib = LazyLibrary()
     called = 0