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

masque/pattern.py

@@ -349,6 +349,16 @@ class Pattern(PortList, AnnotatableImpl, Mirrorable):
         Returns:
             self
         """
+        annotation_conflicts: set[str] = set()
+        if other_pattern.annotations is not None and self.annotations is not None:
+            annotation_conflicts = set(self.annotations.keys()) & set(other_pattern.annotations.keys())
+            if annotation_conflicts:
+                raise PatternError(f'Annotation keys overlap: {annotation_conflicts}')
+
+        port_conflicts = set(self.ports.keys()) & set(other_pattern.ports.keys())
+        if port_conflicts:
+            raise PatternError(f'Port names overlap: {port_conflicts}')
+
         for target, rseq in other_pattern.refs.items():
             self.refs[target].extend(rseq)
         for layer, sseq in other_pattern.shapes.items():
@@ -359,14 +369,7 @@ class Pattern(PortList, AnnotatableImpl, Mirrorable):
         if other_pattern.annotations is not None:
             if self.annotations is None:
                 self.annotations = {}
-            annotation_conflicts = set(self.annotations.keys()) & set(other_pattern.annotations.keys())
-            if annotation_conflicts:
-                raise PatternError(f'Annotation keys overlap: {annotation_conflicts}')
             self.annotations.update(other_pattern.annotations)
-
-        port_conflicts = set(self.ports.keys()) & set(other_pattern.ports.keys())
-        if port_conflicts:
-            raise PatternError(f'Port names overlap: {port_conflicts}')
         self.ports.update(other_pattern.ports)
 
         return self

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))