material.unassign_material - support batching #4474

src/blenderbim/blenderbim/bim/module/geometry/operator.py

@@ -324,8 +324,8 @@ class UpdateRepresentation(bpy.types.Operator, Operator):
                 # We are explicitly casting to a tessellation, so remove all parametric materials.
                 element_type = ifcopenshell.util.element.get_type(product)
                 if element_type:  # Some invalid IFCs use material sets without a type.
-                    ifcopenshell.api.run("material.unassign_material", tool.Ifc.get(), product=element_type)
-                ifcopenshell.api.run("material.unassign_material", tool.Ifc.get(), product=product)
+                    ifcopenshell.api.run("material.unassign_material", tool.Ifc.get(), products=[element_type])
+                ifcopenshell.api.run("material.unassign_material", tool.Ifc.get(), products=[product])
             else:
                 # These objects are parametrically based on an axis and should not be modified as a mesh
                 return

src/blenderbim/blenderbim/bim/module/model/product.py

@@ -551,7 +551,7 @@ def ensure_material_assigned(usecase_path, ifc_file, settings):
 
 
 def ensure_material_unassigned(usecase_path, ifc_file, settings):
-    elements = [settings["product"]]
+    elements = settings["products"]
     if elements[0].is_a("IfcElementType"):
         elements.extend(ifcopenshell.util.element.get_types(elements[0]))
     for element in elements:

src/blenderbim/blenderbim/core/material.py

@@ -116,12 +116,12 @@ def unassign_material(ifc, material_tool, objects):
             inherited_material = material_tool.get_material(element, should_inherit=True)
             if material and "Usage" in material.is_a():
                 element_type = material_tool.get_type(element)
-                ifc.run("material.unassign_material", product=element_type)
+                ifc.run("material.unassign_material", products=[element_type])
             elif not material and inherited_material:
                 element_type = material_tool.get_type(element)
-                ifc.run("material.unassign_material", product=element_type)
+                ifc.run("material.unassign_material", products=[element_type])
             elif material:
-                ifc.run("material.unassign_material", product=element)
+                ifc.run("material.unassign_material", products=[element])
 
 
 def patch_non_parametric_mep_segment(ifc, material_tool, profile_tool, obj):

src/ifcopenshell-python/ifcopenshell/api/__init__.py

@@ -79,15 +79,14 @@ ARGUMENTS_DEPRECATION = {
     "type.unassign_type": partial(
         batching_argument_deprecation, prev_argument="related_object", new_argument="related_objects"
     ),
-    "system.assign_system": partial(
-        batching_argument_deprecation, prev_argument="product", new_argument="products"
-    ),
-    "system.unassign_system": partial(
-        batching_argument_deprecation, prev_argument="product", new_argument="products"
-    ),
+    "system.assign_system": partial(batching_argument_deprecation, prev_argument="product", new_argument="products"),
+    "system.unassign_system": partial(batching_argument_deprecation, prev_argument="product", new_argument="products"),
     "material.assign_material": partial(
         batching_argument_deprecation, prev_argument="product", new_argument="products"
     ),
+    "material.unassign_material": partial(
+        batching_argument_deprecation, prev_argument="product", new_argument="products"
+    ),
 }
 
 

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

@@ -155,10 +155,9 @@ class Usecase:
             return
 
         # NOTE: we always reassign material, even if it might be assigned before
-        for product in self.products:
-            material = ifcopenshell.util.element.get_material(product)
-            if material:
-                ifcopenshell.api.run("material.unassign_material", self.file, product=product)
+        products_to_unassign_material = [p for p in self.products if ifcopenshell.util.element.get_material(p)]
+        if products_to_unassign_material:
+            ifcopenshell.api.run("material.unassign_material", self.file, products=products_to_unassign_material)
 
         if self.settings["type"] == "IfcMaterial" or (
             self.settings["material"] and not self.settings["material"].is_a("IfcMaterial")

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

@@ -17,12 +17,13 @@
 # along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
 
 import ifcopenshell
+import ifcopenshell.api
 import ifcopenshell.util.element
 
 
 class Usecase:
-    def __init__(self, file, product=None):
-        """Removes any material relationship with a product
+    def __init__(self, file: ifcopenshell.file, products: list[ifcopenshell.entity_instance]):
+        """Removes any material relationship with the list of products
 
         A product can only have one material assigned to it, which is why it is
         not necessary to specify the material to unassign. The material is not
@@ -30,8 +31,8 @@ class Usecase:
 
         If the product does not have a material, nothing happens.
 
-        :param product: The IfcProduct that may or may not have a material
-        :type product: ifcopenshell.entity_instance.entity_instance
+        :param products: The list IfcProducts that may or may not have a material
+        :type product: list[ifcopenshell.entity_instance.entity_instance]
         :return: None
         :rtype: None
 
@@ -49,20 +50,34 @@ class Usecase:
             # Let's change our mind and remove the concrete assignment. The
             # concrete material still exists, but the bench is no longer made
             # out of concrete now.
-            ifcopenshell.api.run("material.unassign_material", model, product=bench_type)
+            ifcopenshell.api.run("material.unassign_material", model, products=[bench_type])
         """
         self.file = file
-        self.settings = {"product": product}
+        self.settings = {"products": products}
 
-    def execute(self):
-        if self.settings["product"].is_a("IfcTypeObject"):
-            material = ifcopenshell.util.element.get_material(self.settings["product"])
+    def execute(self) -> None:
+        self.products = set(self.settings["products"])
+        if not self.products:
+            return
+
+        self.remove_material_usages_from_types()
+        self.unassign_materials()
+
+    def remove_material_usages_from_types(self) -> None:
+        # remove material usages from types
+        for product in self.products:
+            if not product.is_a("IfcTypeObject"):
+                continue
+            material = ifcopenshell.util.element.get_material(product)
+            if not material:
+                continue
             if material.is_a() in ["IfcMaterialLayerSet", "IfcMaterialProfileSet"]:
                 # Remove set usages
                 for inverse in self.file.get_inverse(material):
                     if self.file.schema == "IFC2X3":
                         if not inverse.is_a("IfcMaterialLayerSetUsage"):
                             continue
+                        # in IFC2X3 there is no .AssociatedTo
                         for inverse2 in self.file.get_inverse(inverse):
                             if inverse2.is_a("IfcRelAssociatesMaterial"):
                                 history = inverse2.OwnerHistory
@@ -73,21 +88,40 @@ class Usecase:
                         if not inverse.is_a("IfcMaterialUsageDefinition"):
                             continue
                         for rel in inverse.AssociatedTo:
+                            history = rel.OwnerHistory
                             self.file.remove(rel)
+                            if history:
+                                ifcopenshell.util.element.remove_deep2(self.file, history)
                     self.file.remove(inverse)
 
-        for rel in self.settings["product"].HasAssociations:
-            if rel.is_a("IfcRelAssociatesMaterial"):
-                if rel.RelatingMaterial.is_a() in ["IfcMaterialLayerSetUsage", "IfcMaterialProfileSetUsage"]:
+    def unassign_materials(self) -> None:
+        associations: set[ifcopenshell.entity_instance] = set()
+        for product in self.products:
+            associations.update(product.HasAssociations)
+
+        # we ensure that `associations` won't have removed elements
+        # to avoid crash during `material_inverses.issubset(associations)`
+        while associations:
+            rel = next(iter(associations))
+
+            if not rel.is_a("IfcRelAssociatesMaterial"):
+                associations.remove(rel)
+            else:
+                material = rel.RelatingMaterial
+                related_objects = set(rel.RelatedObjects) - self.products
+
+                if material.is_a() in ["IfcMaterialLayerSetUsage", "IfcMaterialProfileSetUsage"]:
                     # Warning: this may leave the model in a non-compliant state.
-                    if self.file.get_total_inverses(rel.RelatingMaterial) == 1 and len(rel.RelatedObjects) == 1:
-                        self.file.remove(rel.RelatingMaterial)
-                if len(rel.RelatedObjects) == 1:
+                    material_inverses = set(self.file.get_inverse(material))
+                    if material_inverses.issubset(associations) and not related_objects:
+                        self.file.remove(material)
+                associations.remove(rel)
+
+                if not related_objects:
                     history = rel.OwnerHistory
                     self.file.remove(rel)
                     if history:
                         ifcopenshell.util.element.remove_deep2(self.file, history)
                     continue
-                related_objects = set(rel.RelatedObjects)
-                related_objects.remove(self.settings["product"])
                 rel.RelatedObjects = list(related_objects)
+                ifcopenshell.api.run("owner.update_owner_history", self.file, **{"element": rel})

src/ifcopenshell-python/ifcopenshell/api/root/remove_product.py

@@ -126,7 +126,7 @@ class Usecase:
                     pset=inverse.RelatingPropertyDefinition,
                 )
             elif inverse.is_a("IfcRelAssociatesMaterial"):
-                ifcopenshell.api.run("material.unassign_material", self.file, product=self.settings["product"])
+                ifcopenshell.api.run("material.unassign_material", self.file, products=[self.settings["product"]])
             elif inverse.is_a("IfcRelDefinesByType"):
                 if inverse.RelatingType == self.settings["product"]:
                     ifcopenshell.api.run("type.unassign_type", self.file, related_objects=inverse.RelatedObjects)

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

@@ -21,16 +21,17 @@ import ifcopenshell.api
 import ifcopenshell.util.element
 
 
-class TestUnassignMaterial(test.bootstrap.IFC4):
+class TestUnassignMaterialIFC2X3(test.bootstrap.IFC2X3):
     def test_unassign_single_material(self):
-        element = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
+        element1 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
+        element2 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
         material = ifcopenshell.api.run("material.add_material", self.file, name="CON01")
         ifcopenshell.api.run(
-            "material.assign_material", self.file, products=[element], type="IfcMaterial", material=material
+            "material.assign_material", self.file, products=[element1, element2], type="IfcMaterial", material=material
         )
-        ifcopenshell.api.run("material.unassign_material", self.file, product=element)
+        ifcopenshell.api.run("material.unassign_material", self.file, products=[element1, element2])
         assert len(self.file.by_type("IfcRelAssociatesMaterial")) == 0
-        assert len(self.file.by_type("IfcWall")) == 1
+        assert len(self.file.by_type("IfcWall")) == 2
         assert len(self.file.by_type("IfcMaterial")) == 1
 
     def test_unassign_single_material_with_multiple_elements(self):
@@ -38,12 +39,9 @@ class TestUnassignMaterial(test.bootstrap.IFC4):
         element2 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
         material = ifcopenshell.api.run("material.add_material", self.file, name="CON01")
         ifcopenshell.api.run(
-            "material.assign_material", self.file, products=[element1], type="IfcMaterial", material=material
+            "material.assign_material", self.file, products=[element1, element2], type="IfcMaterial", material=material
         )
-        ifcopenshell.api.run(
-            "material.assign_material", self.file, products=[element2], type="IfcMaterial", material=material
-        )
-        ifcopenshell.api.run("material.unassign_material", self.file, product=element2)
+        ifcopenshell.api.run("material.unassign_material", self.file, products=[element2])
         assert element1.HasAssociations
         assert not element2.HasAssociations
         assert len(self.file.by_type("IfcRelAssociatesMaterial")) == 1
@@ -51,36 +49,63 @@ class TestUnassignMaterial(test.bootstrap.IFC4):
         assert len(self.file.by_type("IfcMaterial")) == 1
 
     def test_unassign_material_layer_set_from_type(self):
-        element = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWallType")
-        material = ifcopenshell.api.run("material.add_material", self.file, name="CON01")
-        ifcopenshell.api.run("material.assign_material", self.file, products=[element], type="IfcMaterialLayerSet")
-        ifcopenshell.api.run("material.unassign_material", self.file, product=element)
+        element1 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWallType")
+        element2 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWallType")
+        ifcopenshell.api.run(
+            "material.assign_material", self.file, products=[element1, element2], type="IfcMaterialLayerSet"
+        )
+        ifcopenshell.api.run("material.unassign_material", self.file, products=[element1, element2])
         assert len(self.file.by_type("IfcRelAssociatesMaterial")) == 0
-        assert len(self.file.by_type("IfcWallType")) == 1
+        assert len(self.file.by_type("IfcWallType")) == 2
         assert len(self.file.by_type("IfcMaterialLayerSet")) == 1
 
     def test_unassign_material_layer_set_usage_from_element(self):
         element_type = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWallType")
-        element = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
-        ifcopenshell.api.run("type.assign_type", self.file, related_objects=[element], relating_type=element_type)
-        material = ifcopenshell.api.run("material.add_material", self.file, name="CON01")
+        element1 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
+        element2 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
+        ifcopenshell.api.run(
+            "type.assign_type", self.file, related_objects=[element1, element2], relating_type=element_type
+        )
         ifcopenshell.api.run("material.assign_material", self.file, products=[element_type], type="IfcMaterialLayerSet")
-        ifcopenshell.api.run("material.assign_material", self.file, products=[element], type="IfcMaterialLayerSetUsage")
-        ifcopenshell.api.run("material.unassign_material", self.file, product=element)
+        ifcopenshell.api.run(
+            "material.assign_material", self.file, products=[element1, element2], type="IfcMaterialLayerSetUsage"
+        )
+        ifcopenshell.api.run("material.unassign_material", self.file, products=[element1, element2])
         assert len(self.file.by_type("IfcRelAssociatesMaterial")) == 1
         assert element_type.HasAssociations
         assert len(self.file.by_type("IfcWallType")) == 1
-        assert len(self.file.by_type("IfcWall")) == 1
+        assert len(self.file.by_type("IfcWall")) == 2
         assert len(self.file.by_type("IfcMaterialLayerSet")) == 1
         assert len(self.file.by_type("IfcMaterialLayerSetUsage")) == 0
 
+    def test_unassign_material_layer_set_usage_shouldnt_remove_other_usages_of_the_type(self):
+        element_type = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWallType")
+        element1 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
+        element2 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
+        ifcopenshell.api.run(
+            "type.assign_type", self.file, related_objects=[element1, element2], relating_type=element_type
+        )
+        ifcopenshell.api.run("material.assign_material", self.file, products=[element_type], type="IfcMaterialLayerSet")
+        ifcopenshell.api.run(
+            "material.assign_material", self.file, products=[element1], type="IfcMaterialLayerSetUsage"
+        )
+        ifcopenshell.api.run(
+            "material.assign_material", self.file, products=[element2], type="IfcMaterialLayerSetUsage"
+        )
+        ifcopenshell.api.run("material.unassign_material", self.file, products=[element1])
+        assert len(self.file.by_type("IfcRelAssociatesMaterial")) == 2
+        assert element_type.HasAssociations
+        assert len(self.file.by_type("IfcWallType")) == 1
+        assert len(self.file.by_type("IfcWall")) == 2
+        assert len(self.file.by_type("IfcMaterialLayerSet")) == 1
+        assert len(self.file.by_type("IfcMaterialLayerSetUsage")) == 1
+
     def test_unassign_material_layer_set_usage_from_element_with_multiple_invalid_usages(self):
         element_type = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWallType")
         element = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
         element2 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
         ifcopenshell.api.run("type.assign_type", self.file, related_objects=[element], relating_type=element_type)
         ifcopenshell.api.run("type.assign_type", self.file, related_objects=[element2], relating_type=element_type)
-        material = ifcopenshell.api.run("material.add_material", self.file, name="CON01")
         ifcopenshell.api.run("material.assign_material", self.file, products=[element_type], type="IfcMaterialLayerSet")
         rel = ifcopenshell.api.run(
             "material.assign_material", self.file, products=[element], type="IfcMaterialLayerSetUsage"
@@ -89,7 +114,7 @@ class TestUnassignMaterial(test.bootstrap.IFC4):
         # In some invalid IFCs from Revit, they reuse usages. Let's recreate this invalid scenario
         rel.RelatedObjects = list(rel.RelatedObjects) + [element2]
 
-        ifcopenshell.api.run("material.unassign_material", self.file, product=element)
+        ifcopenshell.api.run("material.unassign_material", self.file, products=[element])
 
         assert len(self.file.by_type("IfcRelAssociatesMaterial")) == 2
         for rel in self.file.by_type("IfcRelAssociatesMaterial"):
@@ -102,46 +127,72 @@ class TestUnassignMaterial(test.bootstrap.IFC4):
         assert ifcopenshell.util.element.get_material(element, should_inherit=False) is None
         assert ifcopenshell.util.element.get_material(element2, should_inherit=False).is_a("IfcMaterialLayerSetUsage")
 
-    def test_unassign_material_profile_set_from_type(self):
-        element = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWallType")
-        material = ifcopenshell.api.run("material.add_material", self.file, name="CON01")
-        ifcopenshell.api.run("material.assign_material", self.file, products=[element], type="IfcMaterialProfileSet")
-        ifcopenshell.api.run("material.unassign_material", self.file, product=element)
+    def test_unassign_element_material_list(self):
+        element1 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
+        element2 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
+        material1 = ifcopenshell.api.run("material.add_material", self.file, name="CON01")
+        ifcopenshell.api.run(
+            "material.assign_material",
+            self.file,
+            products=[element1, element2],
+            type="IfcMaterialList",
+            material=material1,
+        )
+        element3 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
+        material3 = ifcopenshell.api.run("material.add_material", self.file, name="CON01")
+        ifcopenshell.api.run(
+            "material.assign_material", self.file, products=[element3], type="IfcMaterialList", material=material3
+        )
+        ifcopenshell.api.run("material.unassign_material", self.file, products=[element1, element2, element3])
         assert len(self.file.by_type("IfcRelAssociatesMaterial")) == 0
-        assert len(self.file.by_type("IfcWallType")) == 1
-        assert len(self.file.by_type("IfcMaterialProfileSet")) == 1
+        assert len(self.file.by_type("IfcMaterialList")) == 2
+        assert len(self.file.by_type("IfcMaterial")) == 2
+
+
+class TestUnassignMaterialIFC4(test.bootstrap.IFC4, TestUnassignMaterialIFC2X3):
+
+    def test_unassign_material_profile_set_from_type(self):
+        element1 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWallType")
+        ifcopenshell.api.run("material.assign_material", self.file, products=[element1], type="IfcMaterialProfileSet")
+        element2 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWallType")
+        ifcopenshell.api.run("material.assign_material", self.file, products=[element2], type="IfcMaterialProfileSet")
+        ifcopenshell.api.run("material.unassign_material", self.file, products=[element1, element2])
+        assert len(self.file.by_type("IfcRelAssociatesMaterial")) == 0
+        assert len(self.file.by_type("IfcWallType")) == 2
+        assert len(self.file.by_type("IfcMaterialProfileSet")) == 2
 
     def test_unassign_material_profile_set_usage_from_element(self):
         element_type = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWallType")
-        element = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
-        ifcopenshell.api.run("type.assign_type", self.file, related_objects=[element], relating_type=element_type)
-        material = ifcopenshell.api.run("material.add_material", self.file, name="CON01")
-        ifcopenshell.api.run("material.assign_material", self.file, products=[element_type], type="IfcMaterialProfileSet")
-        ifcopenshell.api.run("material.assign_material", self.file, products=[element], type="IfcMaterialProfileSetUsage")
-        ifcopenshell.api.run("material.unassign_material", self.file, product=element)
+        element1 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
+        element2 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
+        ifcopenshell.api.run(
+            "type.assign_type", self.file, related_objects=[element1, element2], relating_type=element_type
+        )
+        ifcopenshell.api.run(
+            "material.assign_material", self.file, products=[element_type], type="IfcMaterialProfileSet"
+        )
+        ifcopenshell.api.run(
+            "material.assign_material", self.file, products=[element1, element2], type="IfcMaterialProfileSetUsage"
+        )
+        ifcopenshell.api.run("material.unassign_material", self.file, products=[element1, element2])
         assert len(self.file.by_type("IfcRelAssociatesMaterial")) == 1
         assert element_type.HasAssociations
         assert len(self.file.by_type("IfcWallType")) == 1
-        assert len(self.file.by_type("IfcWall")) == 1
+        assert len(self.file.by_type("IfcWall")) == 2
         assert len(self.file.by_type("IfcMaterialProfileSet")) == 1
         assert len(self.file.by_type("IfcMaterialProfileSetUsage")) == 0
 
     def test_unassign_material_constituent_set_from_type(self):
-        element = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWallType")
-        material = ifcopenshell.api.run("material.add_material", self.file, name="CON01")
-        ifcopenshell.api.run("material.assign_material", self.file, products=[element], type="IfcMaterialConstituentSet")
-        ifcopenshell.api.run("material.unassign_material", self.file, product=element)
-        assert len(self.file.by_type("IfcRelAssociatesMaterial")) == 0
-        assert len(self.file.by_type("IfcWallType")) == 1
-        assert len(self.file.by_type("IfcMaterialConstituentSet")) == 1
-
-    def test_unassign_element_material_list(self):
-        element = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
-        material = ifcopenshell.api.run("material.add_material", self.file, name="CON01")
+        element1 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWallType")
+        element2 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWallType")
         ifcopenshell.api.run(
-            "material.assign_material", self.file, products=[element], type="IfcMaterialList", material=material
+            "material.assign_material", self.file, products=[element1, element2], type="IfcMaterialConstituentSet"
         )
-        ifcopenshell.api.run("material.unassign_material", self.file, product=element)
+        element3 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWallType")
+        ifcopenshell.api.run(
+            "material.assign_material", self.file, products=[element3], type="IfcMaterialConstituentSet"
+        )
+        ifcopenshell.api.run("material.unassign_material", self.file, products=[element1, element2, element3])
         assert len(self.file.by_type("IfcRelAssociatesMaterial")) == 0
-        assert len(self.file.by_type("IfcMaterialList")) == 1
-        assert len(self.file.by_type("IfcMaterial")) == 1
+        assert len(self.file.by_type("IfcWallType")) == 3
+        assert len(self.file.by_type("IfcMaterialConstituentSet")) == 2

src/ifcopenshell-python/test/api/test_api.py

@@ -174,3 +174,15 @@ class TestTemporarySupportForDeprecatedAPIArguments(test.bootstrap.IFC4):
         )
         assert len(self.file.by_type("IfcRelAssociatesMaterial")) == 1
         assert element.HasAssociations[0].RelatingMaterial == material
+
+    @deprecation_check
+    def test_unassign_single_material(self):
+        element = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
+        material = ifcopenshell.api.run("material.add_material", self.file, name="CON01")
+        ifcopenshell.api.run(
+            "material.assign_material", self.file, products=[element], type="IfcMaterial", material=material
+        )
+        ifcopenshell.api.run("material.unassign_material", self.file, product=element)
+        assert len(self.file.by_type("IfcRelAssociatesMaterial")) == 0
+        assert len(self.file.by_type("IfcWall")) == 1
+        assert len(self.file.by_type("IfcMaterial")) == 1