geometry.unassign_representation to remove shape aspects

previously it was leaving unused shape aspects unconnected to any other elements, now it will purge them

src/ifcopenshell-python/ifcopenshell/api/geometry/unassign_representation.py

@@ -50,13 +50,16 @@ class Usecase:
             return
         representations.remove(representation)
         if not representations:
-            self.file.remove(product.Representation)
+            product_def = product.Representation
+            # TODO: should somehow find matching shape aspect and remove it
+            # even before the last representation is removed.
+            self.process_shape_aspects(product_def)
+            self.file.remove(product_def)
         else:
             product.Representation.Representations = representations
 
     def unassign_type_representation(self) -> None:
         matching_representation_map = None
-        representation_maps = self.settings["product"].RepresentationMaps or []
 
         for representation_map in self.settings["product"].RepresentationMaps or []:
             if representation_map.MappedRepresentation == self.settings["representation"]:
@@ -68,8 +71,26 @@ class Usecase:
             self.settings["product"].RepresentationMaps = [
                 rm for rm in self.settings["product"].RepresentationMaps if rm != matching_representation_map
             ] or None
+            self.process_shape_aspects(matching_representation_map)
             self.remove_representation_map_only(matching_representation_map)
 
+    def process_shape_aspects(self, product_representation: ifcopenshell.entity_instance) -> None:
+        # Technically IfcShapeAspect doesn't become invalid when product representation is removed,
+        # but shape aspect makes sense only in context of some other representation.
+        if self.file.schema == "IFC2X3" and product_representation.is_a("IfcRepresentationMap"):
+            shape_aspects = [
+                a
+                for a in self.file.by_type("IfcShapeAspect")
+                if a.PartOfProductDefinitionShape == product_representation
+            ]
+        else:
+            shape_aspects = product_representation.HasShapeAspects
+        for shape_aspect in shape_aspects:
+            representations = shape_aspect.ShapeRepresentations
+            self.file.remove(shape_aspect)
+            for rep in representations:
+                ifcopenshell.api.geometry.remove_representation(self.file, rep)
+
     def remove_representation_map_only(self, representation_map: ifcopenshell.entity_instance) -> None:
         representation_map.MappedRepresentation = self.file.createIfcShapeRepresentation()
         ifcopenshell.util.element.remove_deep2(self.file, representation_map)

src/ifcopenshell-python/test/api/geometry/test_unassign_representation.py

@@ -25,26 +25,41 @@ class TestUnassignRepresentation(test.bootstrap.IFC4):
     def test_unassigning_a_product_representation(self):
         representation = self.file.createIfcShapeRepresentation()
         representation2 = self.file.createIfcShapeRepresentation()
+        item = self.file.create_entity("IfcExtrudedAreaSolid")
+        representation2.Items = (item,)
         wall = self.file.createIfcWall(
             Representation=self.file.createIfcProductDefinitionShape(Representations=[representation, representation2])
         )
+
+        shape_aspect = self.file.create_entity("IfcShapeAspect")
+        shape_aspect.ShapeRepresentations = (self.file.createIfcShapeRepresentation(Items=(item,)),)
+        shape_aspect.PartOfProductDefinitionShape = wall.Representation
+
         ifcopenshell.api.geometry.unassign_representation(self.file, product=wall, representation=representation)
         assert representation not in wall.Representation.Representations
         ifcopenshell.api.geometry.unassign_representation(self.file, product=wall, representation=representation2)
         assert not wall.Representation
         assert len(self.file.by_type("IfcShapeRepresentation")) == 2
         assert len(self.file.by_type("IfcProductDefinitionShape")) == 0
+        assert len(self.file.by_type("IfcShapeAspect")) == 0
 
     def test_unassigning_a_type_product_representation(self):
-        representation = self.file.createIfcShapeRepresentation()
+        item = self.file.create_entity("IfcExtrudedAreaSolid")
+        representation = self.file.createIfcShapeRepresentation(Items=(item,))
         origin = self.file.createIfcAxis2Placement3D()
         repmap = self.file.createIfcRepresentationMap(MappedRepresentation=representation, MappingOrigin=origin)
         walltype = self.file.createIfcWallType(RepresentationMaps=[repmap])
+
+        shape_aspect = self.file.create_entity("IfcShapeAspect")
+        shape_aspect.ShapeRepresentations = (self.file.createIfcShapeRepresentation(Items=(item,)),)
+        shape_aspect.PartOfProductDefinitionShape = repmap
+
         ifcopenshell.api.geometry.unassign_representation(self.file, product=walltype, representation=representation)
         assert not walltype.RepresentationMaps
         assert len(self.file.by_type("IfcAxis2Placement3D")) == 0
         assert len(self.file.by_type("IfcRepresentationMap")) == 0
         assert len(self.file.by_type("IfcShapeRepresentation")) == 1
+        assert len(self.file.by_type("IfcShapeAspect")) == 0
 
     def test_unassigning_a_type_product_representation_used_by_instances(self):
         representation = self.file.createIfcShapeRepresentation()