Inherited and overridden classification references per system is now supported

src/ifcopenshell-python/ifcopenshell/util/classification.py

@@ -24,15 +24,25 @@ def get_references(element, should_inherit=True):
     if should_inherit:
         element_type = ifcopenshell.util.element.get_type(element)
         if element_type and element_type != element:
-            results.update(get_references(element_type))
-    results.update(
-        {
-            r.RelatingClassification
-            for r in getattr(element, "HasAssociations", [])
-            if r.is_a("IfcRelAssociatesClassification")
-        }
-    )
-    return results
+            results = get_references(element_type)
+    occurrence_results = {
+        r.RelatingClassification
+        for r in getattr(element, "HasAssociations", [])
+        if r.is_a("IfcRelAssociatesClassification")
+    }
+    if results:
+        type_references_per_system = {}
+        occurrence_references_per_system = {}
+        for result in results:
+            type_references_per_system.setdefault(get_classification(result), []).append(result)
+        for result in occurrence_results:
+            occurrence_references_per_system.setdefault(get_classification(result), []).append(result)
+        type_references_per_system.update(occurrence_references_per_system)
+        results = set()
+        for values in type_references_per_system.values():
+            [results.add(v) for v in values]
+        return results
+    return occurrence_results
 
 
 def get_classification(reference):

src/ifcopenshell-python/test/util/test_classification.py

@@ -71,7 +71,10 @@ class TestGetReferences(test.bootstrap.IFC4):
             reference=reference2,
             classification=classification,
         )
-        assert subject.get_references(element) == set(self.file.by_type("IfcClassificationReference"))
+        reference1 = [r for r in self.file.by_type("IfcClassificationReference") if r.Identification == "1"][0]
+        reference2 = [r for r in self.file.by_type("IfcClassificationReference") if r.Identification == "2"][0]
+        assert subject.get_references(element_type) == set([reference2])
+        assert subject.get_references(element) == set([reference1])
 
     def test_getting_direct_classifications(self):
         library = ifcopenshell.file()