[Pattern.append] don't dirty pattern if append() fails

masque/test/test_pattern.py

@@ -151,6 +151,33 @@ def test_pattern_interface() -> None:
     assert iface.ports["out_A"].ptype == "test"
 
 
+def test_pattern_append_port_conflict_is_atomic() -> None:
+    pat1 = Pattern()
+    pat1.ports["A"] = Port((0, 0), 0)
+
+    pat2 = Pattern()
+    pat2.polygon((1, 0), vertices=[[0, 0], [1, 0], [0, 1]])
+    pat2.ports["A"] = Port((1, 0), 0)
+
+    with pytest.raises(PatternError, match="Port names overlap"):
+        pat1.append(pat2)
+
+    assert not pat1.shapes
+    assert set(pat1.ports) == {"A"}
+
+
+def test_pattern_append_annotation_conflict_is_atomic() -> None:
+    pat1 = Pattern(annotations={"k": [1]})
+    pat2 = Pattern(annotations={"k": [2]})
+    pat2.polygon((1, 0), vertices=[[0, 0], [1, 0], [0, 1]])
+
+    with pytest.raises(PatternError, match="Annotation keys overlap"):
+        pat1.append(pat2)
+
+    assert not pat1.shapes
+    assert pat1.annotations == {"k": [1]}
+
+
 def test_pattern_deepcopy_does_not_share_shape_repetitions() -> None:
     pat = Pattern()
     pat.polygon((1, 0), vertices=[[0, 0], [1, 0], [0, 1]], repetition=Grid(a_vector=(10, 0), a_count=2))