- apply an import refactoring to the ORM as well

- rework the event system so that event modules load after their
targets, dependencies are reversed
- create an improved strategy lookup system for the ORM
- rework the ORM to have very few import cycles
- move out "importlater" to just util.dependency
- other tricks to cross-populate modules in as clear a way as possible

1 files changed, 13 insertions, 107 deletions

diff --git a/lib/sqlalchemy/orm/attributes.py b/lib/sqlalchemy/orm/attributes.py
index c25792354..949eafca4 100644
--- a/lib/sqlalchemy/orm/attributes.py
+++ b/lib/sqlalchemy/orm/attributes.py
@@ -14,108 +14,17 @@ defines a large part of the ORM's interactivity.
 """
 
 import operator
-from operator import itemgetter
-
 from .. import util, event, inspection
-from . import interfaces, collections, events, exc as orm_exc
-from .instrumentation import instance_state, instance_dict, manager_of_class
+from . import interfaces, collections, exc as orm_exc
 
-orm_util = util.importlater("sqlalchemy.orm", "util")
-
-PASSIVE_NO_RESULT = util.symbol('PASSIVE_NO_RESULT',
-"""Symbol returned by a loader callable or other attribute/history
-retrieval operation when a value could not be determined, based
-on loader callable flags.
-"""
-)
-
-ATTR_WAS_SET = util.symbol('ATTR_WAS_SET',
-"""Symbol returned by a loader callable to indicate the
-retrieved value, or values, were assigned to their attributes
-on the target object.
-""")
-
-ATTR_EMPTY = util.symbol('ATTR_EMPTY',
-"""Symbol used internally to indicate an attribute had no callable.
-""")
-
-NO_VALUE = util.symbol('NO_VALUE',
-"""Symbol which may be placed as the 'previous' value of an attribute,
-indicating no value was loaded for an attribute when it was modified,
-and flags indicated we were not to load it.
-"""
-)
-
-NEVER_SET = util.symbol('NEVER_SET',
-"""Symbol which may be placed as the 'previous' value of an attribute
-indicating that the attribute had not been assigned to previously.
-"""
-)
-
-NO_CHANGE = util.symbol("NO_CHANGE",
-"""No callables or SQL should be emitted on attribute access
-and no state should change""", canonical=0
-)
-
-CALLABLES_OK = util.symbol("CALLABLES_OK",
-"""Loader callables can be fired off if a value
-is not present.""", canonical=1
-)
-
-SQL_OK = util.symbol("SQL_OK",
-"""Loader callables can emit SQL at least on scalar value
-attributes.""", canonical=2)
-
-RELATED_OBJECT_OK = util.symbol("RELATED_OBJECT_OK",
-"""callables can use SQL to load related objects as well
-as scalar value attributes.
-""", canonical=4
-)
-
-INIT_OK = util.symbol("INIT_OK",
-"""Attributes should be initialized with a blank
-value (None or an empty collection) upon get, if no other
-value can be obtained.
-""", canonical=8
-)
-
-NON_PERSISTENT_OK = util.symbol("NON_PERSISTENT_OK",
-"""callables can be emitted if the parent is not persistent.""",
-canonical=16
-)
-
-LOAD_AGAINST_COMMITTED = util.symbol("LOAD_AGAINST_COMMITTED",
-"""callables should use committed values as primary/foreign keys during a load
-""", canonical=32
-)
-
-# pre-packaged sets of flags used as inputs
-PASSIVE_OFF = util.symbol("PASSIVE_OFF",
-    "Callables can be emitted in all cases.",
-    canonical=(RELATED_OBJECT_OK | NON_PERSISTENT_OK |
-                    INIT_OK | CALLABLES_OK | SQL_OK)
-)
-PASSIVE_RETURN_NEVER_SET = util.symbol("PASSIVE_RETURN_NEVER_SET",
-        """PASSIVE_OFF ^ INIT_OK""",
-        canonical=PASSIVE_OFF ^ INIT_OK
-)
-PASSIVE_NO_INITIALIZE = util.symbol("PASSIVE_NO_INITIALIZE",
-        "PASSIVE_RETURN_NEVER_SET ^ CALLABLES_OK",
-        canonical=PASSIVE_RETURN_NEVER_SET ^ CALLABLES_OK
-)
-PASSIVE_NO_FETCH = util.symbol("PASSIVE_NO_FETCH",
-        "PASSIVE_OFF ^ SQL_OK",
-        canonical=PASSIVE_OFF ^ SQL_OK
-)
-PASSIVE_NO_FETCH_RELATED = util.symbol("PASSIVE_NO_FETCH_RELATED",
-        "PASSIVE_OFF ^ RELATED_OBJECT_OK",
-        canonical=PASSIVE_OFF ^ RELATED_OBJECT_OK
-)
-PASSIVE_ONLY_PERSISTENT = util.symbol("PASSIVE_ONLY_PERSISTENT",
-        "PASSIVE_OFF ^ NON_PERSISTENT_OK",
-        canonical=PASSIVE_OFF ^ NON_PERSISTENT_OK
-)
+from .base import instance_state, instance_dict, manager_of_class
 
+from .base import PASSIVE_NO_RESULT, ATTR_WAS_SET, ATTR_EMPTY, NO_VALUE,\
+            NEVER_SET, NO_CHANGE, CALLABLES_OK, SQL_OK, RELATED_OBJECT_OK,\
+            INIT_OK, NON_PERSISTENT_OK, LOAD_AGAINST_COMMITTED, PASSIVE_OFF,\
+            PASSIVE_RETURN_NEVER_SET, PASSIVE_NO_INITIALIZE, PASSIVE_NO_FETCH,\
+            PASSIVE_NO_FETCH_RELATED, PASSIVE_ONLY_PERSISTENT
+from .base import state_str, instance_str
 
 @inspection._self_inspects
 class QueryableAttribute(interfaces._MappedAttribute,
@@ -160,9 +69,6 @@ class QueryableAttribute(interfaces._MappedAttribute,
                 if key in base:
                     self.dispatch._update(base[key].dispatch)
 
-    dispatch = event.dispatcher(events.AttributeEvents)
-    dispatch.dispatch_cls._active_history = False
-
     @util.memoized_property
     def _supports_population(self):
         return self.impl.supports_population
@@ -586,8 +492,8 @@ class AttributeImpl(object):
                             "but the parent record "
                             "has gone stale, can't be sure this "
                             "is the most recent parent." %
-                            (orm_util.state_str(state),
-                            orm_util.state_str(parent_state),
+                            (state_str(state),
+                            state_str(parent_state),
                             self.key))
 
                     return
@@ -839,8 +745,8 @@ class ScalarObjectAttributeImpl(ScalarAttributeImpl):
             else:
                 raise ValueError(
                     "Object %s not associated with %s on attribute '%s'" % (
-                    orm_util.instance_str(check_old),
-                   orm_util.state_str(state),
+                    instance_str(check_old),
+                   state_str(state),
                    self.key
                 ))
         value = self.fire_replace_event(state, dict_, value, old, initiator)
@@ -1131,7 +1037,7 @@ def backref_listeners(attribute, key, uselist):
             'Passing object %s to attribute "%s" '
             'triggers a modify event on attribute "%s" '
             'via the backref "%s".' % (
-                orm_util.state_str(child_state),
+                state_str(child_state),
                 initiator.parent_token,
                 child_impl.parent_token,
                 attribute.impl.parent_token