[ILibraryView / Pattern] flatten() shouldn't drop ports-only patterns if flatten_ports=True

masque/test/test_library.py

@@ -2,7 +2,9 @@ import pytest
 from typing import cast, TYPE_CHECKING
 from ..library import Library, LazyLibrary
 from ..pattern import Pattern
-from ..error import LibraryError
+from ..error import LibraryError, PatternError
+from ..ports import Port
+from ..repetition import Grid
 
 if TYPE_CHECKING:
     from ..shapes import Polygon
@@ -59,6 +61,22 @@ def test_library_flatten() -> None:
     assert tuple(assert_vertices[0]) == (10.0, 10.0)
 
 
+def test_library_flatten_preserves_ports_only_child() -> None:
+    lib = Library()
+    child = Pattern(ports={"P1": Port((1, 2), 0)})
+    lib["child"] = child
+
+    parent = Pattern()
+    parent.ref("child", offset=(10, 10))
+    lib["parent"] = parent
+
+    flat_parent = lib.flatten("parent", flatten_ports=True)["parent"]
+
+    assert set(flat_parent.ports) == {"P1"}
+    assert cast("Port", flat_parent.ports["P1"]).rotation == 0
+    assert tuple(flat_parent.ports["P1"].offset) == (11.0, 12.0)
+
+
 def test_lazy_library() -> None:
     lib = LazyLibrary()
     called = 0