Fix #2756. Bug where reassigning classes with a enum didn't work.

src/blenderbim/test/bim/feature/root.feature

@@ -6,11 +6,12 @@ Scenario: Reassign class
     And I add a cube
     And the object "Cube" is selected
     And I set "scene.BIMRootProperties.ifc_class" to "IfcWall"
-    And I press "bim.assign_class"
+    And I press "bim.assign_class(ifc_class='IfcWall', predefined_type='SOLIDWALL')"
     And I press "object.duplicate_move"
     When the object "IfcWall/Cube.001" is selected
     And I press "bim.enable_reassign_class"
     And I set "scene.BIMRootProperties.ifc_class" to "IfcSlab"
+    And I set "scene.BIMRootProperties.ifc_predefined_type" to "BASESLAB"
     And I press "bim.reassign_class"
     Then the object "IfcSlab/Cube" is an "IfcSlab"
 

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

@@ -20,6 +20,7 @@ import os
 import json
 import time
 import ifcopenshell
+import ifcopenshell.util.attribute
 
 # This is highly experimental and incomplete, however, it may work for simple datasets.
 # In this simple implementation, we only support 2X3<->4 right now
@@ -76,7 +77,11 @@ def reassign_class(ifc_file, element, new_class):
         name = attribute.name()
         old_attribute = info.get(name, None)
         if old_attribute:
-            new_attributes[name] = old_attribute
+            if ifcopenshell.util.attribute.get_primitive_type(attribute) == "enum":
+                if old_attribute in ifcopenshell.util.attribute.get_enum_items(attribute):
+                    new_attributes[name] = old_attribute
+            else:
+                new_attributes[name] = old_attribute
 
     inverse_pairs = ifc_file.get_inverse(element, allow_duplicate=True, with_attribute_indices=True)
     ifc_file.remove(element)

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

@@ -26,6 +26,7 @@ def is_x(value, x):
 
 
 def get_volume(geometry):
+    # https://stackoverflow.com/questions/1406029/how-to-calculate-the-volume-of-a-3d-mesh-object-the-surface-of-which-is-made-up
     def signed_triangle_volume(p1, p2, p3):
         v321 = p3[0] * p2[1] * p1[2]
         v231 = p2[0] * p3[1] * p1[2]