- 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, 25 insertions, 25 deletions

diff --git a/lib/sqlalchemy/orm/session.py b/lib/sqlalchemy/orm/session.py
index 89d9946ee..3cc03a2d4 100644
--- a/lib/sqlalchemy/orm/session.py
+++ b/lib/sqlalchemy/orm/session.py
@@ -518,28 +518,28 @@ class Session(_SessionClassMethods):
             :ref:`session_autocommit`
 
         :param autoflush: When ``True``, all query operations will issue a
-           :meth:`~.Session.flush` call to this ``Session`` before proceeding. 
-           This is a convenience feature so that :meth:`~.Session.flush` need 
-           not be called repeatedly in order for database queries to retrieve 
+           :meth:`~.Session.flush` call to this ``Session`` before proceeding.
+           This is a convenience feature so that :meth:`~.Session.flush` need
+           not be called repeatedly in order for database queries to retrieve
            results. It's typical that ``autoflush`` is used in conjunction with
            ``autocommit=False``. In this scenario, explicit calls to
-           :meth:`~.Session.flush` are rarely needed; you usually only need to 
+           :meth:`~.Session.flush` are rarely needed; you usually only need to
            call :meth:`~.Session.commit` (which flushes) to finalize changes.
 
-        :param bind: An optional :class:`.Engine` or :class:`.Connection` to 
-           which this ``Session`` should be bound. When specified, all SQL 
-           operations performed by this session will execute via this 
+        :param bind: An optional :class:`.Engine` or :class:`.Connection` to
+           which this ``Session`` should be bound. When specified, all SQL
+           operations performed by this session will execute via this
            connectable.
 
         :param binds: An optional dictionary which contains more granular
            "bind" information than the ``bind`` parameter provides. This
-           dictionary can map individual :class`.Table` 
-           instances as well as :class:`~.Mapper` instances to individual 
-           :class:`.Engine` or :class:`.Connection` objects. Operations which 
-           proceed relative to a particular :class:`.Mapper` will consult this 
-           dictionary for the direct :class:`.Mapper` instance as 
-           well as the mapper's ``mapped_table`` attribute in order to locate a 
-           connectable to use. The full resolution is described in the 
+           dictionary can map individual :class`.Table`
+           instances as well as :class:`~.Mapper` instances to individual
+           :class:`.Engine` or :class:`.Connection` objects. Operations which
+           proceed relative to a particular :class:`.Mapper` will consult this
+           dictionary for the direct :class:`.Mapper` instance as
+           well as the mapper's ``mapped_table`` attribute in order to locate a
+           connectable to use. The full resolution is described in the
            :meth:`.Session.get_bind`.
            Usage looks like::
 
@@ -566,8 +566,8 @@ class Session(_SessionClassMethods):
            :meth:`~.Session.begin`, all of which are interdependent.
 
         :param expire_on_commit:  Defaults to ``True``. When ``True``, all
-           instances will be fully expired after each :meth:`~.commit`, 
-           so that all attribute/object access subsequent to a completed 
+           instances will be fully expired after each :meth:`~.commit`,
+           so that all attribute/object access subsequent to a completed
            transaction will load from the most recent database state.
 
         :param extension: An optional
@@ -585,16 +585,16 @@ class Session(_SessionClassMethods):
            .. versionadded:: 0.9.0
 
         :param query_cls:  Class which should be used to create new Query
-           objects, as returned by the :meth:`~.Session.query` method. Defaults 
+           objects, as returned by the :meth:`~.Session.query` method. Defaults
            to :class:`.Query`.
 
         :param twophase:  When ``True``, all transactions will be started as
             a "two phase" transaction, i.e. using the "two phase" semantics
-            of the database in use along with an XID.  During a 
-            :meth:`~.commit`, after :meth:`~.flush` has been issued for all 
+            of the database in use along with an XID.  During a
+            :meth:`~.commit`, after :meth:`~.flush` has been issued for all
             attached databases, the :meth:`~.TwoPhaseTransaction.prepare` method
-            on each database's :class:`.TwoPhaseTransaction` will be called. 
-            This allows each database to roll back the entire transaction, 
+            on each database's :class:`.TwoPhaseTransaction` will be called.
+            This allows each database to roll back the entire transaction,
             before each transaction is committed.
 
         :param weak_identity_map:  Defaults to ``True`` - when set to
@@ -1048,7 +1048,7 @@ class Session(_SessionClassMethods):
         bind
           Any Connectable: a :class:`.Engine` or :class:`.Connection`.
 
-        All subsequent operations involving this :class:`.Table` will use the 
+        All subsequent operations involving this :class:`.Table` will use the
         given `bind`.
 
         """
@@ -1149,7 +1149,7 @@ class Session(_SessionClassMethods):
             ', '.join(context)))
 
     def query(self, *entities, **kwargs):
-        """Return a new :class:`.Query` object corresponding to this 
+        """Return a new :class:`.Query` object corresponding to this
         :class:`.Session`."""
 
         return self._query_cls(entities, self, **kwargs)
@@ -1403,7 +1403,7 @@ class Session(_SessionClassMethods):
 
                 instance_key = mapper._identity_key_from_state(state)
 
-                if _none_set.issubset(instance_key[1]) and \
+                if _none_set.intersection(instance_key[1]) and \
                     not mapper.allow_partial_pks or \
                     _none_set.issuperset(instance_key[1]):
                     raise exc.FlushError(
@@ -1635,7 +1635,7 @@ class Session(_SessionClassMethods):
             self._update_impl(merged_state)
             new_instance = True
 
-        elif not _none_set.issubset(key[1]) or \
+        elif not _none_set.intersection(key[1]) or \
                     (mapper.allow_partial_pks and
                     not _none_set.issuperset(key[1])):
             merged = self.query(mapper.class_).get(key[1])