Made objects clear more handlers on deletion, also scramble some methods and all database access wrappers to avoid an object memory instance being accessed after it has been deleted. See #509.

src/commands/default/building.py

@@ -542,7 +542,7 @@ class CmdDestroy(MuxCommand):
             # do the deletion
             okay = obj.delete()
             if not okay:
-                string += "\nERROR: %s not deleted, probably because at_obj_delete() returned False." % objname
+                string += "\nERROR: %s not deleted, probably because delete() returned False." % objname
             else:
                 string += "\n%s was destroyed." % objname
                 if had_exits:

src/typeclasses/models.py

@@ -32,6 +32,7 @@ import traceback
 import weakref
 
 from django.db import models
+from django.core.exceptions import ObjectDoesNotExist
 from django.conf import settings
 from django.utils.encoding import smart_str
 from django.contrib.contenttypes.models import ContentType
@@ -1183,15 +1184,36 @@ class TypedObject(SharedMemoryModel):
                        if hperm in perms and hpos > ppos)
         return False
 
+    #
+    # Deletion methods
+    #
+
+    def _deleted(self, *args, **kwargs):
+        "Scrambling method for already deleted objects"
+        raise ObjectDoesNotExist("This object was already deleted!")
+
+    _is_deleted = False # this is checked by db_* wrappers
+
     def delete(self):
         "Cleaning up handlers on the typeclass level"
         global TICKER_HANDLER
         if not TICKER_HANDLER:
             from src.scripts.tickerhandler import TICKER_HANDLER
-        TICKER_HANDLER.remove(self) # removes all ticker subscriptions
-        _GA(self, "permissions").clear()
+        TICKER_HANDLER.remove(self) # removes objects' all ticker subscriptions
+        if not isinstance(_GA(self, "permissions"), LazyLoadHandler):
+            _GA(self, "permissions").clear()
+        if not isinstance(_GA(self, "attributes"), LazyLoadHandler):
+            _GA(self, "attributes").clear()
+        if not isinstance(_GA(self, "aliases"), LazyLoadHandler):
+            _GA(self, "aliases").clear()
+        if not isinstance(_GA(self, "nicks"), LazyLoadHandler):
+            _GA(self, "nicks").clear()
         _SA(self, "_cached_typeclass", None)
         _GA(self, "flush_from_cache")()
+
+        # scrambling properties
+        self.delete = self._deleted
+        self._is_deleted = True
         super(TypedObject, self).delete()
 
     #

src/utils/idmapper/base.py

@@ -86,9 +86,13 @@ class SharedMemoryModelBase(ModelBase):
             def _get(cls, fname):
                 "Wrapper for getting database field"
                 #print "_get:", fieldname, wrappername,_GA(cls,fieldname)
+                if _GA(cls, "_is_deleted"):
+                    raise ObjectDoesNotExist("Cannot access %s: Hosting object was already deleted." % fname)
                 return _GA(cls, fieldname)
             def _get_foreign(cls, fname):
                 "Wrapper for returing foreignkey fields"
+                if _GA(cls, "_is_deleted"):
+                    raise ObjectDoesNotExist("Cannot access %s: Hosting object was already deleted." % fname)
                 value = _GA(cls, fieldname)
                 #print "_get_foreign:value:", value
                 try:
@@ -100,6 +104,8 @@ class SharedMemoryModelBase(ModelBase):
                 raise FieldError("Field %s cannot be edited." % fname)
             def _set(cls, fname, value):
                 "Wrapper for setting database field"
+                if _GA(cls, "_is_deleted"):
+                    raise ObjectDoesNotExist("Cannot set %s to %s: Hosting object was already deleted!" % (fname, value))
                 _SA(cls, fname, value)
                 # only use explicit update_fields in save if we actually have a
                 # primary key assigned already (won't be set when first creating object)
@@ -107,6 +113,8 @@ class SharedMemoryModelBase(ModelBase):
                 _GA(cls, "save")(update_fields=update_fields)
             def _set_foreign(cls, fname, value):
                 "Setter only used on foreign key relations, allows setting with #dbref"
+                if _GA(cls, "_is_deleted"):
+                    raise ObjectDoesNotExist("Cannot set %s to %s: Hosting object was already deleted!" % (fname, value))
                 try:
                     value = _GA(value, "dbobj")
                 except AttributeError:
@@ -348,7 +356,7 @@ def flush_cached_instance(sender, instance, **kwargs):
     # XXX: Is this the best way to make sure we can flush?
     if not hasattr(instance, 'flush_cached_instance'):
         return
-    sender.flush_cached_instance(instance)
+    sender.flush_cached_instance(instance, force=True)
 pre_delete.connect(flush_cached_instance)