#2471 work around file gc with instance refs

src/ifcopenshell-python/ifcopenshell/entity_instance.py

@@ -107,20 +107,36 @@ class entity_instance(object):
             e = ifcopenshell_wrapper.new_IfcBaseClass(*e)
         super(entity_instance, self).__setattr__("wrapped_data", e)
         super(entity_instance, self).__setattr__("method_list", None)
+
+        # Make sure the file is not gc'ed while we have live instances
         self.wrapped_data.file = file
 
+    def __del__(self):
+        """
+        #2471 while the precise chain of action is unclear, creating
+        instance references prevents file gc, even with all instance
+        refs deleted. This is a work-around for that.
+        """
+        self.wrapped_data.file = None
+
     def __getattr__(self, name):
         INVALID, FORWARD, INVERSE = range(3)
         attr_cat = self.wrapped_data.get_attribute_category(name)
         if attr_cat == FORWARD:
             return entity_instance.wrap_value(
-                self.wrapped_data.get_argument(self.wrapped_data.get_argument_index(name)), self.wrapped_data.file
+                self.wrapped_data.get_argument(
+                    self.wrapped_data.get_argument_index(name)
+                ),
+                self.wrapped_data.file,
             )
         elif attr_cat == INVERSE:
-            return entity_instance.wrap_value(self.wrapped_data.get_inverse(name), self.wrapped_data.file)
+            return entity_instance.wrap_value(
+                self.wrapped_data.get_inverse(name), self.wrapped_data.file
+            )
         else:
             raise AttributeError(
-                "entity instance of type '%s' has no attribute '%s'" % (self.wrapped_data.is_a(True), name)
+                "entity instance of type '%s' has no attribute '%s'"
+                % (self.wrapped_data.is_a(True), name)
             )
 
     @staticmethod
@@ -159,7 +175,11 @@ class entity_instance(object):
         :type attr: int
         :rtype: string
         """
-        attr_idx = attr if isinstance(attr, numbers.Integral) else self.wrapped_data.get_argument_index(attr)
+        attr_idx = (
+            attr
+            if isinstance(attr, numbers.Integral)
+            else self.wrapped_data.get_argument_index(attr)
+        )
         return self.wrapped_data.get_argument_type(attr_idx)
 
     def attribute_name(self, attr_idx):
@@ -177,15 +197,23 @@ class entity_instance(object):
 
     def __getitem__(self, key):
         if key < 0 or key >= len(self):
-            raise IndexError("Attribute index {} out of range for instance of type {}".format(key, self.is_a()))
+            raise IndexError(
-        return entity_instance.wrap_value(self.wrapped_data.get_argument(key), self.wrapped_data.file)
+                "Attribute index {} out of range for instance of type {}".format(
+                    key, self.is_a()
+                )
+            )
+        return entity_instance.wrap_value(
+            self.wrapped_data.get_argument(key), self.wrapped_data.file
+        )
 
     def __setitem__(self, idx, value):
         if self.wrapped_data.file and self.wrapped_data.file.transaction:
             self.wrapped_data.file.transaction.store_edit(self, idx, value)
 
         if self.method_list is None:
-            super(entity_instance, self).__setattr__("method_list", _method_dict[self.is_a(True)])
+            super(entity_instance, self).__setattr__(
+                "method_list", _method_dict[self.is_a(True)]
+            )
 
         method = self.method_list[idx]
 
@@ -193,7 +221,9 @@ class entity_instance(object):
             if method is not set_derived_atribute:
                 self.wrapped_data.setArgumentAsNull(idx)
         else:
-            self.method_list[idx](self.wrapped_data, idx, entity_instance.unwrap_value(value))
+            self.method_list[idx](
+                self.wrapped_data, idx, entity_instance.unwrap_value(value)
+            )
 
         return value
 
@@ -240,8 +270,11 @@ class entity_instance(object):
         if self.id():
             return self.wrapped_data == other.wrapped_data
         else:
-            return (self.is_a(), self[0], self.wrapped_data.file_pointer()) == \
+            return (self.is_a(), self[0], self.wrapped_data.file_pointer()) == (
-                (other.is_a(), other[0], other.wrapped_data.file_pointer())
+                other.is_a(),
+                other[0],
+                other.wrapped_data.file_pointer(),
+            )
 
     def __hash__(self):
         # Proper entity instances have a stable identity by means of the numeric
@@ -263,7 +296,9 @@ class entity_instance(object):
             )
         )
 
-    def get_info(self, include_identifier=True, recursive=False, return_type=dict, ignore=()):
+    def get_info(
+        self, include_identifier=True, recursive=False, return_type=dict, ignore=()
+    ):
         """Return a dictionary of the entity_instance's properties (Python and IFC) and their values.
 
         :param include_identifier: Whether or not to include the STEP numerical identifier
@@ -293,7 +328,11 @@ class entity_instance(object):
                     yield "id", self.id()
                 yield "type", self.is_a()
             except BaseException:
-                logging.exception("unhandled exception while getting id / type info on {}".format(self))
+                logging.exception(
+                    "unhandled exception while getting id / type info on {}".format(
+                        self
+                    )
+                )
             for i in range(len(self)):
                 try:
                     if self.wrapped_data.get_attribute_names()[i] in ignore:
@@ -316,16 +355,24 @@ class entity_instance(object):
                                 ignore=ignore,
                             )
 
-                        attr_value = entity_instance.walk(is_instance, get_info_, attr_value)
+                        attr_value = entity_instance.walk(
+                            is_instance, get_info_, attr_value
+                        )
                     yield self.attribute_name(i), attr_value
                 except BaseException:
-                    logging.exception("unhandled exception occurred setting attribute name for {}".format(self))
+                    logging.exception(
+                        "unhandled exception occurred setting attribute name for {}".format(
+                            self
+                        )
+                    )
 
         return return_type(_())
 
     __dict__ = property(get_info)
 
-    def get_info_2(self, include_identifier=True, recursive=False, return_type=dict, ignore=()):
+    def get_info_2(
+        self, include_identifier=True, recursive=False, return_type=dict, ignore=()
+    ):
         assert include_identifier
         assert recursive
         assert return_type is dict