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

masque/library.py

@@ -303,7 +303,8 @@ class ILibraryView(Mapping[str, 'Pattern'], metaclass=ABCMeta):
                 target_pat = flattened[target]
                 if target_pat is None:
                     raise PatternError(f'Circular reference in {name} to {target}')
-                if target_pat.is_empty():        # avoid some extra allocations
+                ports_only = flatten_ports and bool(target_pat.ports)
+                if target_pat.is_empty() and not ports_only:        # avoid some extra allocations
                     continue
 
                 for ref in pat.refs[target]:

masque/pattern.py

@@ -1077,7 +1077,8 @@ class Pattern(PortList, AnnotatableImpl, Mirrorable):
 
                 if target_pat is None:
                     raise PatternError(f'Circular reference in {name} to {target}')
-                if target_pat.is_empty():        # avoid some extra allocations
+                ports_only = flatten_ports and bool(target_pat.ports)
+                if target_pat.is_empty() and not ports_only:        # avoid some extra allocations
                     continue
 
                 for ref in refs:

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

masque/test/test_pattern.py

@@ -1,12 +1,15 @@
+import pytest
 from typing import cast
 from numpy.testing import assert_equal, assert_allclose
 from numpy import pi
 
+from ..error import PatternError
 from ..pattern import Pattern
 from ..shapes import Polygon
 from ..ref import Ref
 from ..ports import Port
 from ..label import Label
+from ..repetition import Grid
 
 
 def test_pattern_init() -> None:
@@ -99,6 +102,18 @@ def test_pattern_get_bounds() -> None:
     assert_equal(bounds, [[-5, -5], [10, 10]])
 
 
+def test_pattern_flatten_preserves_ports_only_child() -> None:
+    child = Pattern(ports={"P1": Port((1, 2), 0)})
+
+    parent = Pattern()
+    parent.ref("child", offset=(10, 10))
+
+    parent.flatten({"child": child}, flatten_ports=True)
+
+    assert set(parent.ports) == {"P1"}
+    assert parent.ports["P1"].rotation == 0
+    assert tuple(parent.ports["P1"].offset) == (11.0, 12.0)
+
 def test_pattern_interface() -> None:
     source = Pattern()
     source.ports["A"] = Port((10, 20), 0, ptype="test")