material.remove_material_set to remove usages

To prevent them from being invalidated.

Noticed this as a possible issue investigating https://community.osarch.org/discussion/2820/error-message-in-bonsai-bim

src/ifcopenshell-python/ifcopenshell/api/material/remove_material_set.py

@@ -17,6 +17,7 @@
 # along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
 
 import ifcopenshell
+import ifcopenshell.api.material
 import ifcopenshell.util.element
 
 
@@ -24,7 +25,9 @@ def remove_material_set(file: ifcopenshell.file, material: ifcopenshell.entity_i
     """Removes a material set
 
     All set items, such as layers, profiles, or constituents will also be
-    removed. However, the materials and profile curves used by the layers,
+    removed. All set usages are also removed.
+
+    However, the materials and profile curves used by the layers,
     profiles and constituents will not be removed.
 
     :param material: The IfcMaterialLayerSet, IfcMaterialConstituentSet,
@@ -53,7 +56,15 @@ def remove_material_set(file: ifcopenshell.file, material: ifcopenshell.entity_i
         ifcopenshell.api.material.remove_material_set(model, material=material_set)
     """
 
-    inverse_elements = file.get_inverse(material)
+    # Remove all usages for sets.
+    has_usages = material.is_a("IfcMaterialLayerSet") or material.is_a("IfcMaterialProfileSet")
+    if has_usages:
+        # Usage is invalid if it is not associated with some element,
+        # so we can remove usages through unassignment.
+        elements = ifcopenshell.util.element.get_elements_by_material(file, material)
+        if elements:
+            ifcopenshell.api.material.unassign_material(file, products=list(elements))
+
     if material.is_a("IfcMaterialLayerSet"):
         set_items = material.MaterialLayers or []
     elif material.is_a("IfcMaterialProfileSet"):
@@ -66,9 +77,13 @@ def remove_material_set(file: ifcopenshell.file, material: ifcopenshell.entity_i
         raise ValueError(f"Unknown material set type: {material.is_a()}")
     for set_item in set_items:
         file.remove(set_item)
+
+    inverse_elements = file.get_inverse(material)
     file.remove(material)
+
     for inverse in inverse_elements:
         if inverse.is_a("IfcRelAssociatesMaterial"):
+            # NOTE: for has_usages already handled by unassign_material.
             history = inverse.OwnerHistory
             file.remove(inverse)
             if history:

src/ifcopenshell-python/ifcopenshell/api/material/unassign_material.py

@@ -31,6 +31,9 @@ def unassign_material(file: ifcopenshell.file, products: list[ifcopenshell.entit
 
     If the product does not have a material, nothing happens.
 
+    Unassigning a LayerSet or ProfileSet from the product type will also
+    remove all Usages of the set.
+
     :param products: The list IfcProducts that may or may not have a material
     :return: None
 
@@ -76,6 +79,8 @@ class Usecase:
                 continue
             if material.is_a() in ["IfcMaterialLayerSet", "IfcMaterialProfileSet"]:
                 # Remove set usages
+                # TODO: be more considerate and remove only usages
+                # associated with the set + product type, not all usages?
                 for inverse in self.file.get_inverse(material):
                     if self.file.schema == "IFC2X3":
                         if not inverse.is_a("IfcMaterialLayerSetUsage"):

src/ifcopenshell-python/test/api/material/test_remove_material_set.py

@@ -17,9 +17,10 @@
 # along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
 
 import test.bootstrap
+import ifcopenshell.api.material
 import ifcopenshell.api.pset
 import ifcopenshell.api.root
-import ifcopenshell.api.material
+import ifcopenshell.api.type
 
 
 class TestRemoveMaterialSetIFC2X3(test.bootstrap.IFC2X3):
@@ -45,6 +46,19 @@ class TestRemoveMaterialSetIFC2X3(test.bootstrap.IFC2X3):
         assert len(self.file.by_type("IfcMaterialLayer")) == 0
         assert len(self.file.by_type("IfcMaterial")) == 1
 
+    def test_removing_a_material_set_with_usages(self):
+        material = ifcopenshell.api.material.add_material_set(self.file, set_type="IfcMaterialLayerSet")
+        element_type = ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcWallType")
+        element = ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcWall")
+        ifcopenshell.api.type.assign_type(self.file, related_objects=[element], relating_type=element_type)
+        ifcopenshell.api.material.assign_material(self.file, products=[element_type], material=material)
+        ifcopenshell.api.material.assign_material(
+            self.file, products=[element], material=material, type="IfcMaterialLayerSetUsage"
+        )
+        ifcopenshell.api.material.remove_material_set(self.file, material=material)
+        assert len(self.file.by_type("IfcMaterialLayerSet")) == 0
+        assert len(self.file.by_type("IfcMaterialLayerSetUsage")) == 0
+
 
 class TestRemoveMaterialSetIFC4(test.bootstrap.IFC4, TestRemoveMaterialSetIFC2X3):
     # IFC2X3 doesn't support adding a pset to IfcMaterialLayerSet