Adjusted inplace-binops on set-based collections and association proxies to

more closely follow builtin (2.4+) set semantics.  Formerly any set duck-type
was accepted, now only types or subtypes of set, frozenset or the collection
type itself are accepted.

2 files changed, 35 insertions, 13 deletions

diff --git a/lib/sqlalchemy/ext/associationproxy.py b/lib/sqlalchemy/ext/associationproxy.py
index bcbfb4780..d878f7b9b 100644
--- a/lib/sqlalchemy/ext/associationproxy.py
+++ b/lib/sqlalchemy/ext/associationproxy.py
@@ -6,10 +6,12 @@ transparent proxied access to the endpoint of an association object.
 See the example ``examples/association/proxied_association.py``.
 """
 
-import weakref, itertools
-import sqlalchemy.exceptions as exceptions
-import sqlalchemy.orm as orm
-import sqlalchemy.util as util
+import itertools
+import weakref
+from sqlalchemy import exceptions
+from sqlalchemy import orm
+from sqlalchemy import util
+from sqlalchemy.orm import collections
 
 
 def association_proxy(targetcollection, attr, **kw):
@@ -702,7 +704,7 @@ class _AssociationSet(object):
             self.add(value)
 
     def __ior__(self, other):
-        if util.duck_type_collection(other) is not util.Set:
+        if not collections._set_binops_check_strict(self, other):
             return NotImplemented
         for value in other:
             self.add(value)
@@ -726,7 +728,7 @@ class _AssociationSet(object):
             self.discard(value)
 
     def __isub__(self, other):
-        if util.duck_type_collection(other) is not util.Set:
+        if not collections._set_binops_check_strict(self, other):
             return NotImplemented
         for value in other:
             self.discard(value)
@@ -748,7 +750,7 @@ class _AssociationSet(object):
             self.add(value)
 
     def __iand__(self, other):
-        if util.duck_type_collection(other) is not util.Set:
+        if not collections._set_binops_check_strict(self, other):
             return NotImplemented
         want, have = self.intersection(other), util.Set(self)
 
@@ -776,7 +778,7 @@ class _AssociationSet(object):
             self.add(value)
 
     def __ixor__(self, other):
-        if util.duck_type_collection(other) is not util.Set:
+        if not collections._set_binops_check_strict(self, other):
             return NotImplemented
         want, have = self.symmetric_difference(other), util.Set(self)
 
diff --git a/lib/sqlalchemy/orm/collections.py b/lib/sqlalchemy/orm/collections.py
index 8067a030f..c8fc2f189 100644
--- a/lib/sqlalchemy/orm/collections.py
+++ b/lib/sqlalchemy/orm/collections.py
@@ -95,7 +95,11 @@ The owning object and InstrumentedCollectionAttribute are also reachable
 through the adapter, allowing for some very sophisticated behavior.
 """
 
-import copy, inspect, sys, weakref
+import copy
+import inspect
+import sets
+import sys
+import weakref
 
 from sqlalchemy import exceptions, schema, util as sautil
 from sqlalchemy.util import attrgetter, Set
@@ -1136,6 +1140,22 @@ def _dict_decorators():
     l.pop('Unspecified')
     return l
 
+
+try:
+    _set_binop_bases = (set, frozenset, sets.BaseSet)
+except NameError:
+    _set_binop_bases = (sets.BaseSet,)
+
+def _set_binops_check_strict(self, obj):
+    """Allow only set, frozenset and self.__class__-derived objects in binops."""
+    return isinstance(obj, _set_binop_bases + (self.__class__,))
+
+def _set_binops_check_loose(self, obj):
+    """Allow anything set-like to participate in set binops."""
+    return (isinstance(obj, _set_binop_bases + (self.__class__,)) or
+            sautil.duck_type_collection(obj) == sautil.Set)
+
+
 def _set_decorators():
     """Hand-turned instrumentation wrappers that can decorate any set-like
     sequence class."""
@@ -1208,7 +1228,7 @@ def _set_decorators():
 
     def __ior__(fn):
         def __ior__(self, value):
-            if sautil.duck_type_collection(value) is not Set:
+            if not _set_binops_check_strict(self, value):
                 return NotImplemented
             for item in value:
                 self.add(item)
@@ -1225,7 +1245,7 @@ def _set_decorators():
 
     def __isub__(fn):
         def __isub__(self, value):
-            if sautil.duck_type_collection(value) is not Set:
+            if not _set_binops_check_strict(self, value):
                 return NotImplemented
             for item in value:
                 self.discard(item)
@@ -1247,7 +1267,7 @@ def _set_decorators():
 
     def __iand__(fn):
         def __iand__(self, other):
-            if sautil.duck_type_collection(other) is not Set:
+            if not _set_binops_check_strict(self, other):
                 return NotImplemented
             want, have = self.intersection(other), Set(self)
             remove, add = have - want, want - have
@@ -1274,7 +1294,7 @@ def _set_decorators():
 
     def __ixor__(fn):
         def __ixor__(self, other):
-            if sautil.duck_type_collection(other) is not Set:
+            if not _set_binops_check_strict(self, other):
                 return NotImplemented
             want, have = self.symmetric_difference(other), Set(self)
             remove, add = have - want, want - have