- Adjustment to attribute mechanics concerning when a value is

implicitly initialized to None via first access; this action,
which has always resulted in a population of the attribute,
now emits an attribute event just like any other attribute set
operation and generates the same kind of history as one.  Additionally,
many mapper internal operations will no longer implicitly generate
these "None" values when various never-set attributes are checked.
These are subtle behavioral fixes to attribute mechanics which provide
a better solution to the problem of :ticket:`3060`, which also
involves recognition of attributes explicitly set to ``None``
vs. attributes that were never set.
fixes #3061

1 files changed, 9 insertions, 7 deletions

diff --git a/lib/sqlalchemy/orm/mapper.py b/lib/sqlalchemy/orm/mapper.py
index 3e93840a1..373e18271 100644
--- a/lib/sqlalchemy/orm/mapper.py
+++ b/lib/sqlalchemy/orm/mapper.py
@@ -24,6 +24,7 @@ from .. import sql, util, log, exc as sa_exc, event, schema, inspection
 from ..sql import expression, visitors, operators, util as sql_util
 from . import instrumentation, attributes, exc as orm_exc, loading
 from . import properties
+from . import util as orm_util
 from .interfaces import MapperProperty, _InspectionAttr, _MappedAttribute
 
 from .base import _class_to_mapper, _state_mapper, class_mapper, \
@@ -2270,7 +2271,7 @@ class Mapper(_InspectionAttr):
         manager = state.manager
         return self._identity_class, tuple([
             manager[self._columntoproperty[col].key].\
-                impl.get(state, dict_, attributes.PASSIVE_OFF)
+                impl.get(state, dict_, attributes.PASSIVE_RETURN_NEVER_SET)
             for col in self.primary_key
         ])
 
@@ -2292,12 +2293,13 @@ class Mapper(_InspectionAttr):
         manager = state.manager
         return [
             manager[self._columntoproperty[col].key].\
-                impl.get(state, dict_, attributes.PASSIVE_OFF)
+                impl.get(state, dict_,
+                                attributes.PASSIVE_RETURN_NEVER_SET)
             for col in self.primary_key
         ]
 
     def _get_state_attr_by_column(self, state, dict_, column,
-                                    passive=attributes.PASSIVE_OFF):
+                        passive=attributes.PASSIVE_RETURN_NEVER_SET):
         prop = self._columntoproperty[column]
         return state.manager[prop.key].impl.get(state, dict_, passive=passive)
 
@@ -2311,7 +2313,8 @@ class Mapper(_InspectionAttr):
         return self._get_committed_state_attr_by_column(state, dict_, column)
 
     def _get_committed_state_attr_by_column(self, state, dict_,
-                        column, passive=attributes.PASSIVE_OFF):
+                        column,
+                        passive=attributes.PASSIVE_RETURN_NEVER_SET):
 
         prop = self._columntoproperty[column]
         return state.manager[prop.key].impl.\
@@ -2352,7 +2355,7 @@ class Mapper(_InspectionAttr):
                                     state, state.dict,
                                     leftcol,
                                     passive=attributes.PASSIVE_NO_INITIALIZE)
-                if leftval is attributes.PASSIVE_NO_RESULT or leftval is None:
+                if leftval in orm_util._none_set:
                     raise ColumnsNotAvailable()
                 binary.left = sql.bindparam(None, leftval,
                                             type_=binary.right.type)
@@ -2361,8 +2364,7 @@ class Mapper(_InspectionAttr):
                                     state, state.dict,
                                     rightcol,
                                     passive=attributes.PASSIVE_NO_INITIALIZE)
-                if rightval is attributes.PASSIVE_NO_RESULT or \
-                            rightval is None:
+                if rightval in orm_util._none_set:
                     raise ColumnsNotAvailable()
                 binary.right = sql.bindparam(None, rightval,
                                             type_=binary.right.type)