Don't apply sets or similar to objects in IdentitySet

Modified the internal "identity set" implementation, which is a set that
hashes objects on their id() rather than their hash values, to not actually
call the ``__hash__()`` method of the objects, which are typically
user-mapped objects.  Some methods were calling this method as a side
effect of the implementation.

Fixes: #5304
Change-Id: I0ed8762f47622215a54dcad9f210377b1becf8e8

1 files changed, 27 insertions, 44 deletions

diff --git a/lib/sqlalchemy/util/_collections.py b/lib/sqlalchemy/util/_collections.py
index b21eb44cf..10d80fc98 100644
--- a/lib/sqlalchemy/util/_collections.py
+++ b/lib/sqlalchemy/util/_collections.py
@@ -363,13 +363,10 @@ class IdentitySet(object):
 
     """
 
-    _working_set = set
-
     def __init__(self, iterable=None):
         self._members = dict()
         if iterable:
-            for o in iterable:
-                self.add(o)
+            self.update(iterable)
 
     def add(self, value):
         self._members[id(value)] = value
@@ -412,7 +409,7 @@ class IdentitySet(object):
             return True
 
     def issubset(self, iterable):
-        other = type(self)(iterable)
+        other = self.__class__(iterable)
 
         if len(self) > len(other):
             return False
@@ -433,7 +430,7 @@ class IdentitySet(object):
         return len(self) < len(other) and self.issubset(other)
 
     def issuperset(self, iterable):
-        other = type(self)(iterable)
+        other = self.__class__(iterable)
 
         if len(self) < len(other):
             return False
@@ -455,11 +452,10 @@ class IdentitySet(object):
         return len(self) > len(other) and self.issuperset(other)
 
     def union(self, iterable):
-        result = type(self)()
-        # testlib.pragma exempt:__hash__
-        members = self._member_id_tuples()
-        other = _iter_id(iterable)
-        result._members.update(self._working_set(members).union(other))
+        result = self.__class__()
+        members = self._members
+        result._members.update(members)
+        result._members.update((id(obj), obj) for obj in iterable)
         return result
 
     def __or__(self, other):
@@ -468,7 +464,7 @@ class IdentitySet(object):
         return self.union(other)
 
     def update(self, iterable):
-        self._members = self.union(iterable)._members
+        self._members.update((id(obj), obj) for obj in iterable)
 
     def __ior__(self, other):
         if not isinstance(other, IdentitySet):
@@ -477,11 +473,12 @@ class IdentitySet(object):
         return self
 
     def difference(self, iterable):
-        result = type(self)()
-        # testlib.pragma exempt:__hash__
-        members = self._member_id_tuples()
-        other = _iter_id(iterable)
-        result._members.update(self._working_set(members).difference(other))
+        result = self.__class__()
+        members = self._members
+        other = {id(obj) for obj in iterable}
+        result._members.update(
+            ((k, v) for k, v in members.items() if k not in other)
+        )
         return result
 
     def __sub__(self, other):
@@ -499,11 +496,12 @@ class IdentitySet(object):
         return self
 
     def intersection(self, iterable):
-        result = type(self)()
-        # testlib.pragma exempt:__hash__
-        members = self._member_id_tuples()
-        other = _iter_id(iterable)
-        result._members.update(self._working_set(members).intersection(other))
+        result = self.__class__()
+        members = self._members
+        other = {id(obj) for obj in iterable}
+        result._members.update(
+            (k, v) for k, v in members.items() if k in other
+        )
         return result
 
     def __and__(self, other):
@@ -521,18 +519,17 @@ class IdentitySet(object):
         return self
 
     def symmetric_difference(self, iterable):
-        result = type(self)()
-        # testlib.pragma exempt:__hash__
-        members = self._member_id_tuples()
-        other = _iter_id(iterable)
+        result = self.__class__()
+        members = self._members
+        other = {id(obj): obj for obj in iterable}
         result._members.update(
-            self._working_set(members).symmetric_difference(other)
+            ((k, v) for k, v in members.items() if k not in other)
+        )
+        result._members.update(
+            ((k, v) for k, v in other.items() if k not in members)
         )
         return result
 
-    def _member_id_tuples(self):
-        return ((id(v), v) for v in self._members.values())
-
     def __xor__(self, other):
         if not isinstance(other, IdentitySet):
             return NotImplemented
@@ -600,13 +597,6 @@ class WeakSequence(object):
 
 
 class OrderedIdentitySet(IdentitySet):
-    class _working_set(OrderedSet):
-        # a testing pragma: exempt the OIDS working set from the test suite's
-        # "never call the user's __hash__" assertions.  this is a big hammer,
-        # but it's safe here: IDS operates on (id, instance) tuples in the
-        # working set.
-        __sa_hash_exempt__ = True
-
     def __init__(self, iterable=None):
         IdentitySet.__init__(self)
         self._members = OrderedDict()
@@ -942,13 +932,6 @@ class ThreadLocalRegistry(ScopedRegistry):
             pass
 
 
-def _iter_id(iterable):
-    """Generator: ((id(o), o) for o in iterable)."""
-
-    for item in iterable:
-        yield id(item), item
-
-
 def has_dupes(sequence, target):
     """Given a sequence and search object, return True if there's more
     than one, False if zero or one of them.