Fix tests, clean up file creating empty project

To fix tests changed bim.unlink_object not to unlink original blender materials as they might be used elsewhere.

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

@@ -118,7 +118,7 @@ class AddMaterial(bpy.types.Operator, tool.Ifc.Operator):
     bl_idname = "bim.add_material"
     bl_label = "Add Material"
     bl_options = {"REGISTER", "UNDO"}
-    obj: bpy.props.StringProperty()
+    obj: bpy.props.StringProperty(name="Material Name")
     name: bpy.props.StringProperty(default="Default")
 
     def invoke(self, context, event):

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

@@ -113,6 +113,10 @@ class CreateProject(bpy.types.Operator):
         if tool.Blender.is_default_scene():
             for obj in bpy.data.objects:
                 bpy.data.objects.remove(obj)
+            for mesh in bpy.data.meshes:
+                bpy.data.meshes.remove(mesh)
+            for mat in bpy.data.materials:
+                bpy.data.materials.remove(mat)
         core.create_project(tool.Ifc, tool.Project, schema=props.export_schema, template=template)
         tool.Blender.register_toolbar()
 

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

@@ -215,7 +215,7 @@ class UnlinkObject(bpy.types.Operator):
     bl_idname = "bim.unlink_object"
     bl_label = "Unlink Object"
     bl_options = {"REGISTER", "UNDO"}
-    obj: bpy.props.StringProperty()
+    obj: bpy.props.StringProperty(name="Object Name")
     should_delete: bpy.props.BoolProperty(name="Delete IFC Element", default=True)
 
     def execute(self, context):
@@ -227,6 +227,7 @@ class UnlinkObject(bpy.types.Operator):
         else:
             objects = context.selected_objects
 
+        objects: list[bpy.types.Object]
         for obj in objects:
             was_active_object = obj == context.active_object
 
@@ -242,6 +243,27 @@ class UnlinkObject(bpy.types.Operator):
                 if obj.data:
                     obj_copy.data = obj.data.copy()
 
+                    # prevent unlinking materials that might be used elsewhere
+                    replacements: dict[bpy.types.Material, bpy.types.Material] = dict()
+                    for material_slot in obj_copy.material_slots:
+                        material = material_slot.material
+                        if material is None:
+                            continue
+
+                        if material in replacements:
+                            material_replacement = replacements[material]
+
+                        # no need to copy non-ifc materials as unlinking won't do anything to them
+                        elif tool.Ifc.get_entity(material) is None and tool.Style.get_style(material) is None:
+                            replacements[material] = material
+                            continue
+
+                        else:
+                            material_replacement = material.copy()
+                            replacements[material] = material_replacement
+
+                        material_slot.material = material_replacement
+
                 tool.Geometry.delete_ifc_object(obj)
 
                 obj = obj_copy

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

@@ -24,7 +24,7 @@ Scenario: Unlink object
     And I set "scene.BIMRootProperties.ifc_product" to "IfcElement"
     And I set "scene.BIMRootProperties.ifc_class" to "IfcWall"
     And I press "bim.assign_class"
-    And I press "bim.add_material"
+    And I press "bim.add_style()"
     When I press "bim.unlink_object(obj='IfcWall/Cube')"
     Then the object "Cube" is not an IFC element
     And the material "Material" is an IFC style