ifcpatch: fix MergeDuplicateTypes destroying distinct/cross-class types

MergeDuplicateTypes grouped IfcTypeObjects by a single attribute value
only, which caused two failures:

- With should_merge_null=True (the old default), every type with an empty
  Tag was treated as a duplicate and collapsed into one. On Bonsai-authored
  or mixed models this silently destroyed distinct, differently-named types
  (e.g. array-child proxy types), leaving BBIM_Array parents pointing at
  removed child GUIDs ("Arrays With Missing Children" on reload).
- Ignoring the IFC class let unrelated types merge, raising e.g.
  "IfcTypeProduct cannot type IfcBeam" from assign_type.

Include the IFC class in the merge key so only same-class types merge, and
default should_merge_null to False so untagged types are kept separate
unless explicitly opted in via ["Tag", True]. Genuine Revit duplicates
always carry a populated Tag, so the target workflow is unaffected.

Adds regression tests: distinct null-attribute types preserved by default,
and cross-class types never merged.

See https://github.com/IfcOpenShell/IfcOpenShell/issues/8609

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/ifcpatch/ifcpatch/recipes/MergeDuplicateTypes.py

@@ -25,7 +25,7 @@ import ifcopenshell.util.element
 
 
 class Patcher:
-    def __init__(self, file: ifcopenshell.file, logger: Logger, attribute: str = "Tag", should_merge_null: bool = True):
+    def __init__(self, file: ifcopenshell.file, logger: Logger, attribute: str = "Tag", should_merge_null: bool = False):
         """Merge duplicate element types via the Tag or another attribute
 
         Revit is notorious for creating many duplicate element types. Element
@@ -50,8 +50,18 @@ class Patcher:
         :param attribute: The name of the attribute to merge element types based
             on. Typically this will be "Tag" as it stores the unique ID from the
             proprietary BIM software.
-        :param should_merge_null: If True, all elements with an empty attribute
+        Only types of the same IFC class are ever merged, so e.g. an
-            will be merged. If False, they will be kept separate.
+        annotation type and a beam type that happen to share an attribute value
+        are never combined.
+
+        :param should_merge_null: If True, all types with an empty attribute
+            will be merged together. This defaults to False because an empty
+            attribute is an absence of evidence, not proof of duplication:
+            merging every untagged type into one silently destroys distinct
+            types (a common failure on Bonsai-authored or mixed models, where
+            genuine, differently-named types may all lack a Tag). Genuine Revit
+            duplicates always carry a populated Tag, so the default only affects
+            types the recipe has no reason to believe are duplicates.
 
         Example:
 
@@ -62,6 +72,9 @@ class Patcher:
 
             # Explicitly say we want to merge based on the Name attribute
             ifcpatch.execute({"file": model, "recipe": "MergeDuplicateTypes", "arguments": ["Name"]})
+
+            # Also merge all types that have an empty Tag into a single type
+            ifcpatch.execute({"file": model, "recipe": "MergeDuplicateTypes", "arguments": ["Tag", True]})
         """
         self.file = file
         self.logger = logger
@@ -71,9 +84,15 @@ class Patcher:
     def patch(self):
         keys: dict[Any, ifcopenshell.entity_instance] = {}
         for element_type in self.file.by_type("IfcTypeObject"):
-            key = getattr(element_type, self.attribute)
+            attribute_value = getattr(element_type, self.attribute)
-            if not key and not self.should_merge_null:
+            if not attribute_value and not self.should_merge_null:
                 continue
+            # Include the IFC class in the key so that only types of the same
+            # class are ever merged. Two types of different classes are not
+            # duplicates, and merging them would reassign occurrences to an
+            # incompatible type (e.g. an IfcTypeProduct used for annotations
+            # cannot type an IfcBeam), raising a TypeError in assign_type.
+            key = (element_type.is_a(), attribute_value)
             original_type = keys.get(key, None)
             if original_type:
                 elements = ifcopenshell.util.element.get_types(element_type)

src/ifcpatch/test/test_MergeDuplicateTypes.py

@@ -72,6 +72,35 @@ class TestMergeDuplicateTypes(test.bootstrap.IFC4):
         assert ifcopenshell.util.element.get_material(wall1, should_inherit=False) == None
         assert ifcopenshell.util.element.get_material(wall2, should_inherit=False) == None
 
+    def test_not_merging_different_classes(self):
+        # Types of different classes are not duplicates even if they share the
+        # merge attribute (here an empty Tag). Merging them would try to
+        # reassign occurrences to an incompatible type. See the IfcTypeProduct
+        # (annotation) vs IfcBeam case.
+        annotation_type = ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcTypeProduct")
+        annotation = ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcAnnotation")
+        ifcopenshell.api.type.assign_type(
+            self.file, related_objects=[annotation], relating_type=annotation_type, should_map_representations=False
+        )
+        beam_type = ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcBeamType")
+        beam = ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcBeam")
+        ifcopenshell.api.type.assign_type(
+            self.file, related_objects=[beam], relating_type=beam_type, should_map_representations=False
+        )
+        output = ifcpatch.execute({"file": self.file, "recipe": "MergeDuplicateTypes", "arguments": ["Tag", True]})
+        assert len(output.by_type("IfcTypeProduct")) == 2
+        assert output.by_type("IfcBeamType")
+
+    def test_empty_attributes_kept_separate_by_default(self):
+        # An empty attribute is an absence of evidence, not proof of
+        # duplication. By default (should_merge_null=False) distinct types that
+        # merely lack a Tag must be preserved, otherwise e.g. differently-named
+        # Bonsai-authored types get silently collapsed into one.
+        for name in ("Wire Ladder", "CMU Core", "Mortar Joint"):
+            ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcBuildingElementProxyType", name=name)
+        output = ifcpatch.execute({"file": self.file, "recipe": "MergeDuplicateTypes", "arguments": []})
+        assert len(output.by_type("IfcBuildingElementProxyType")) == 3
+
     def test_not_merging_empty_attributes(self):
         wall_type1 = ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcWallType", name="")
         wall_type2 = ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcWallType", name="")