Purge unused materials to consider materials with styles and psets #3914

If material has a style or a pset it creates an inverse that shouldn't prevent material from being purged.

src/bonsai/bonsai/bim/module/debug/operator.py

@@ -632,14 +632,11 @@ class PurgeUnusedObjects(bpy.types.Operator, tool.Ifc.Operator):
         elif object_type == "PROFILE":
             purged = bonsai.core.profile.purge_unused_profiles(tool.Ifc, tool.Profile)
         elif object_type == "STYLE":
+            # It's okay to remove IfcPresentationStyle if just remove_deep
+            # as there are no white listed inverses.
             purged = tool.Debug.purge_unused_class("IfcPresentationStyle")
         elif object_type == "MATERIAL":
-            ifc_file = tool.Ifc.get()
-            is_ifc2x3 = ifc_file.schema == "IFC2X3"
-            if is_ifc2x3:
-                purged = tool.Debug.purge_unused_class("IfcMaterial")
-            else:
-                purged = tool.Debug.purge_unused_class("IfcMaterialDefinition")
+            purged = tool.Material.purge_unused_materials()
         else:
             self.report({"ERROR"}, f"Invalid object type {object_type}.")
             return {"CANCELLED"}

src/bonsai/bonsai/tool/material.py

@@ -388,3 +388,29 @@ class Material(bonsai.core.tool.Material):
             material.Materials = [default_material]
         else:
             assert False, f"Invalid material type found: {material_type}."
+
+    @classmethod
+    def purge_unused_materials(cls) -> int:
+        ifc_file = tool.Ifc.get()
+        is_ifc2x3 = ifc_file.schema == "IFC2X3"
+        ifc_class = "IfcMaterial" if is_ifc2x3 else "IfcMaterialDefinition"
+
+        skip_inverses = {
+            "IfcMaterialDefinitionRepresentation",
+            "IfcMaterialProperties",
+        }
+
+        def is_safe_to_purge(material: ifcopenshell.entity_instance) -> bool:
+            for i in ifc_file.get_inverse(material):
+                if i.is_a() not in skip_inverses:
+                    return False
+            return True
+
+        materials = ifc_file.by_type(ifc_class)
+        i = 0
+        for material in materials:
+            if ifc_file.get_total_inverses(material) != 0 and not is_safe_to_purge(material):
+                continue
+            ifcopenshell.api.material.remove_material(ifc_file, material)
+            i += 1
+        return i

src/bonsai/test/tool/test_material.py

@@ -19,6 +19,9 @@
 import bpy
 import ifcopenshell
 import ifcopenshell.api
+import ifcopenshell.api.material
+import ifcopenshell.api.pset
+import ifcopenshell.api.style
 import bonsai.core.tool
 import bonsai.tool as tool
 from test.bim.bootstrap import NewFile
@@ -183,3 +186,19 @@ class TestEnsureNewMaterialSetIsValid(NewFile):
         material_set = ifc.create_entity("IfcMaterialList")
         subject.ensure_new_material_set_is_valid(material_set)
         assert len(material_set.Materials) == 1
+
+
+class TestPurgeUnusedMaterials(NewFile):
+    def test_run(self):
+        ifc = ifcopenshell.file()
+        tool.Ifc.set(ifc)
+        material = ifcopenshell.api.material.add_material(ifc)
+        # Add pset.
+        ifcopenshell.api.pset.add_pset(ifc, material, "Foo")
+        # Add style.
+        style = ifcopenshell.api.style.add_style(ifc)
+        context = ifc.create_entity("IfcRepresentationContext")
+        ifcopenshell.api.style.assign_material_style(ifc, material, style, context)
+
+        assert subject.purge_unused_materials() == 1
+        assert not ifc.by_type("IfcMaterial")