Fix #3069. WARNING: dangerous change. Objects that have their own collection now have a pointer to that collection. This fixes a variety of subtle sync bugs.

src/blenderbim/blenderbim/bim/__init__.py

@@ -111,6 +111,7 @@ classes = [
     prop.PsetQto,
     prop.GlobalId,
     prop.BIMObjectProperties,
+    prop.BIMCollectionProperties,
     prop.BIMMaterialProperties,
     prop.BIMMeshProperties,
     ui.BIM_PT_section_plane,
@@ -158,6 +159,7 @@ def register():
     bpy.app.handlers.load_post.append(handler.loadIfcStore)
     bpy.app.handlers.save_post.append(handler.ensureIfcExported)
     bpy.types.Scene.BIMProperties = bpy.props.PointerProperty(type=prop.BIMProperties)
+    bpy.types.Collection.BIMCollectionProperties = bpy.props.PointerProperty(type=prop.BIMCollectionProperties)
     bpy.types.Object.BIMObjectProperties = bpy.props.PointerProperty(type=prop.BIMObjectProperties)
     bpy.types.Material.BIMObjectProperties = bpy.props.PointerProperty(type=prop.BIMObjectProperties)
     bpy.types.Material.BIMMaterialProperties = bpy.props.PointerProperty(type=prop.BIMMaterialProperties)
@@ -195,6 +197,7 @@ def unregister():
     bpy.app.handlers.load_post.remove(handler.loadIfcStore)
     bpy.app.handlers.save_post.remove(handler.ensureIfcExported)
     del bpy.types.Scene.BIMProperties
+    del bpy.types.Collection.BIMCollectionProperties
     del bpy.types.Object.BIMObjectProperties
     del bpy.types.Material.BIMObjectProperties
     del bpy.types.Material.BIMMaterialProperties

src/blenderbim/blenderbim/bim/import_ifc.py

@@ -1337,8 +1337,9 @@ class IfcImporter:
             "{}/{}".format(self.project["ifc"].is_a(), self.project["ifc"].Name)
         )
         obj = self.create_product(self.project["ifc"])
-        if obj:
-            self.project["blender"].objects.link(obj)
+        self.project["blender"].objects.link(obj)
+        self.project["blender"].BIMCollectionProperties.obj = obj
+        obj.BIMObjectProperties.collection = self.project["blender"]
 
     def create_collections(self):
         if self.ifc_import_settings.collection_mode == "DECOMPOSITION":
@@ -1673,6 +1674,8 @@ class IfcImporter:
             return
         elif element.GlobalId in self.collections:
             collection = self.collections[element.GlobalId]
+            collection.BIMCollectionProperties.obj = obj
+            obj.BIMObjectProperties.collection = collection
             collection.name = obj.name
             return collection.objects.link(obj)
         elif getattr(element, "Decomposes", None):
@@ -1687,7 +1690,10 @@ class IfcImporter:
         elif element.is_a("IfcGridAxis"):
             return
         elif element.GlobalId in self.collections:
-            return self.collections[element.GlobalId].objects.link(obj)
+            collection = self.collections[element.GlobalId]
+            collection.BIMCollectionProperties.obj = obj
+            obj.BIMObjectProperties.collection = collection
+            return collection.objects.link(obj)
         elif element.is_a("IfcTypeObject"):
             return self.type_collection.objects.link(obj)
         elif element.is_a("IfcStructuralMember"):

src/blenderbim/blenderbim/bim/prop.py

@@ -409,7 +409,12 @@ class GlobalId(PropertyGroup):
     name: StringProperty(name="Name")
 
 
+class BIMCollectionProperties(PropertyGroup):
+    obj: PointerProperty(type=bpy.types.Object)
+
+
 class BIMObjectProperties(PropertyGroup):
+    collection: PointerProperty(type=bpy.types.Collection)
     ifc_definition_id: IntProperty(name="IFC Definition ID")
     blender_offset_type: EnumProperty(
         items=[(o, o, "") for o in ["NONE", "OBJECT_PLACEMENT", "CARTESIAN_POINT"]],

src/blenderbim/blenderbim/tool/collector.py

@@ -59,17 +59,18 @@ class Collector(blenderbim.core.tool.Collector):
                     parent_collection = collection
                     break
 
-        if parent_collection:
-            parent_obj = bpy.data.objects.get(parent_collection.name)
-            parent = tool.Ifc.get_entity(parent_obj)
-            if parent:
-                # This is lazy, but works. One of these will succeed, the other will fail silently.
-                blenderbim.core.spatial.assign_container(
-                    tool.Ifc, tool.Collector, tool.Spatial, structure_obj=parent_obj, element_obj=obj
-                )
-                blenderbim.core.aggregate.assign_object(
-                    tool.Ifc, tool.Aggregate, tool.Collector, relating_obj=parent_obj, related_obj=obj
-                )
+        if not parent_collection:
+            return
+
+        parent = tool.Ifc.get_entity(parent_collection.BIMCollectionProperties.obj)
+        if parent:
+            # This is lazy, but works. One of these will succeed, the other will fail silently.
+            blenderbim.core.spatial.assign_container(
+                tool.Ifc, tool.Collector, tool.Spatial, structure_obj=parent_obj, element_obj=obj
+            )
+            blenderbim.core.aggregate.assign_object(
+                tool.Ifc, tool.Aggregate, tool.Collector, relating_obj=parent_obj, related_obj=obj
+            )
 
     @classmethod
     def assign(cls, obj):
@@ -100,18 +101,21 @@ class Collector(blenderbim.core.tool.Collector):
 
     @classmethod
     def _get_own_collection(cls, element, obj):
+        if obj.BIMObjectProperties.collection:
+            return obj.BIMObjectProperties.collection
+
         if element.is_a("IfcProject"):
-            return bpy.data.collections.get(obj.name) or bpy.data.collections.new(obj.name)
+            return cls._create_own_collection(obj)
 
         if tool.Ifc.get_schema() == "IFC2X3":
             if element.is_a("IfcSpatialStructureElement"):
-                return bpy.data.collections.get(obj.name) or bpy.data.collections.new(obj.name)
+                return cls._create_own_collection(obj)
         else:
             if element.is_a("IfcSpatialStructureElement") or element.is_a("IfcExternalSpatialStructureElement"):
-                return bpy.data.collections.get(obj.name) or bpy.data.collections.new(obj.name)
+                return cls._create_own_collection(obj)
 
         if element.is_a("IfcGrid"):
-            return bpy.data.collections.get(obj.name) or bpy.data.collections.new(obj.name)
+            return cls._create_own_collection(obj)
 
         if element.is_a("IfcGridAxis"):
             if element.PartOfU:
@@ -125,7 +129,7 @@ class Collector(blenderbim.core.tool.Collector):
                 axes = "WAxes"
             grid_obj = tool.Ifc.get_object(grid)
             if grid_obj:
-                grid_col = bpy.data.collections.get(grid_obj.name)
+                grid_col = cls._get_own_collection(grid, grid_obj)
                 axes_col = [c for c in grid_col.children if axes in c.name]
                 if axes_col:
                     return axes_col[0]
@@ -144,7 +148,7 @@ class Collector(blenderbim.core.tool.Collector):
             return bpy.data.collections.get("Connections") or bpy.data.collections.new("Connections")
 
         if getattr(element, "IsDecomposedBy", None):
-            return bpy.data.collections.get(obj.name) or bpy.data.collections.new(obj.name)
+            return cls._create_own_collection(obj)
 
     @classmethod
     def _get_collection(cls, element, obj):
@@ -180,14 +184,14 @@ class Collector(blenderbim.core.tool.Collector):
         if aggregate:
             aggregate_obj = tool.Ifc.get_object(aggregate)
             if aggregate_obj:
-                collection = bpy.data.collections.get(aggregate_obj.name)
+                collection = aggregate_obj.BIMObjectProperties.collection
                 if collection:
                     return collection
 
         container = ifcopenshell.util.element.get_container(element)
         if container:
             container_obj = tool.Ifc.get_object(container)
-            collection = bpy.data.collections.get(container_obj.name)
+            collection = container_obj.BIMObjectProperties.collection
             if collection:
                 return collection
 
@@ -208,3 +212,10 @@ class Collector(blenderbim.core.tool.Collector):
             project_obj = tool.Ifc.get_object(tool.Ifc.get().by_type("IfcProject")[0])
             project_obj.users_collection[0].children.link(collection)
         return collection
+
+    @classmethod
+    def _create_own_collection(cls, obj):
+        collection = bpy.data.collections.new(obj.name)
+        obj.BIMObjectProperties.collection = collection
+        collection.BIMCollectionProperties.obj = obj
+        return collection

src/blenderbim/test/tool/test_collector.py

@@ -153,6 +153,7 @@ class TestAssign(NewFile):
         tool.Ifc.link(space_element, space_obj)
         space_collection = bpy.data.collections.new("IfcSpace/Name")
         bpy.context.scene.collection.children.link(space_collection)
+        space_obj.BIMObjectProperties.collection = space_collection
         space_collection.objects.link(space_obj)
         ifcopenshell.api.run(
             "aggregate.assign_object",