Include a field's interface in equality and hashing.

Fixes #40

CHANGES.rst

@@ -30,6 +30,16 @@
   compatibility problem. See `issue 36
   <https://github.com/zopefoundation/zope.schema/issues/36>`_.
 
+- ``Field`` instances are only equal when their ``.interface`` is
+  equal. In practice, this means that two otherwise identical fields
+  of separate schemas are not equal, do not hash the same, and can
+  both be members of the same ``dict`` or ``set``. Prior to this
+  release, when hashing was identity based but only worked on Python
+  2, that was the typical behaviour. (Field objects that are *not*
+  members of a schema continue to compare and hash equal if they have
+  the same attributes and interfaces.) See `issue 40
+  <https://github.com/zopefoundation/zope.schema/issues/40>`_.
+
 - Orderable fields, including ``Int``, ``Float``, ``Decimal``,
   ``Timedelta``, ``Date`` and ``Time``, can now have a
   ``missing_value`` without needing to specify concrete ``min`` and

src/zope/schema/_bootstrapfields.py

@@ -119,7 +119,7 @@ class Field(Attribute):
     default = DefaultProperty('default')
 
     # These were declared as slots in zope.interface, we override them here to
-    # get rid of the dedcriptors so they don't break .bind()
+    # get rid of the descriptors so they don't break .bind()
     __name__ = None
     interface = None
     _Element__tagged_values = None
@@ -206,21 +206,24 @@ def __get_property_names_to_compare(self):
             names.update(getFields(interface))
 
         # order will be different always, don't compare it
-        if 'order' in names:
-            del names['order']
+        names.pop('order', None)
         return names
 
     def __hash__(self):
         # Equal objects should have equal hashes;
         # equal hashes does not imply equal objects.
-        value = (type(self),) + tuple(self.__get_property_names_to_compare())
+        value = (type(self), self.interface) + tuple(self.__get_property_names_to_compare())
         return hash(value)
 
     def __eq__(self, other):
-        # should be the same type
-        if type(self) != type(other):
+        # should be the same type and in the same interface (or no interface at all)
+        if self is other:
+            return True
+
+        if type(self) != type(other) or self.interface != other.interface:
             return False
 
+
         # should have the same properties
         names = self.__get_property_names_to_compare()
         # XXX: What about the property names of the other object? Even

src/zope/schema/tests/test__bootstrapfields.py

@@ -142,7 +142,88 @@ def _factory(context):
         self.assertEqual(_called_with, [inst.context])
 
 
-class FieldTests(unittest.TestCase):
+class EqualityTestsMixin(object):
+
+    def _getTargetClass(self):
+        raise NotImplementedError
+
+    def _makeOne(self, *args, **kw):
+        return self._getTargetClass()(*args, **kw)
+
+    def test_is_hashable(self):
+        field = self._makeOne()
+        hash(field)  # doesn't raise
+
+    def test_equal_instances_have_same_hash(self):
+        # Equal objects should have equal hashes
+        field1 = self._makeOne()
+        field2 = self._makeOne()
+        self.assertIsNot(field1, field2)
+        self.assertEqual(field1, field2)
+        self.assertEqual(hash(field1), hash(field2))
+
+    def test_instances_in_different_interfaces_not_equal(self):
+        from zope import interface
+
+        field1 = self._makeOne()
+        field2 = self._makeOne()
+        self.assertEqual(field1, field2)
+        self.assertEqual(hash(field1), hash(field2))
+
+        class IOne(interface.Interface):
+            one = field1
+
+        class ITwo(interface.Interface):
+            two = field2
+
+        self.assertEqual(field1, field1)
+        self.assertEqual(field2, field2)
+        self.assertNotEqual(field1, field2)
+        self.assertNotEqual(hash(field1), hash(field2))
+
+    def test_hash_across_unequal_instances(self):
+        # Hash equality does not imply equal objects.
+        # Our implementation only considers property names,
+        # not values. That's OK, a dict still does the right thing.
+        field1 = self._makeOne(title=u'foo')
+        field2 = self._makeOne(title=u'bar')
+        self.assertIsNot(field1, field2)
+        self.assertNotEqual(field1, field2)
+        self.assertEqual(hash(field1), hash(field2))
+
+        d = {field1: 42}
+        self.assertIn(field1, d)
+        self.assertEqual(42, d[field1])
+        self.assertNotIn(field2, d)
+        with self.assertRaises(KeyError):
+            d.__getitem__(field2)
+
+    def test___eq___different_type(self):
+        left = self._makeOne()
+
+        class Derived(self._getTargetClass()):
+            pass
+        right = Derived()
+        self.assertNotEqual(left, right)
+        self.assertTrue(left != right)
+
+    def test___eq___same_type_different_attrs(self):
+        left = self._makeOne(required=True)
+        right = self._makeOne(required=False)
+        self.assertNotEqual(left, right)
+        self.assertTrue(left != right)
+
+    def test___eq___same_type_same_attrs(self):
+        left = self._makeOne()
+        self.assertEqual(left, left)
+
+        right = self._makeOne()
+        self.assertEqual(left, right)
+        self.assertFalse(left != right)
+
+
+class FieldTests(EqualityTestsMixin,
+                 unittest.TestCase):
 
     def _getTargetClass(self):
         from zope.schema._bootstrapfields import Field
@@ -304,27 +385,6 @@ def _fail(value):
         field._type = int
         field.validate(1)  # doesn't raise
 
-    def test___eq___different_type(self):
-        left = self._makeOne()
-
-        class Derived(self._getTargetClass()):
-            pass
-        right = Derived()
-        self.assertEqual(left == right, False)
-        self.assertEqual(left != right, True)
-
-    def test___eq___same_type_different_attrs(self):
-        left = self._makeOne(required=True)
-        right = self._makeOne(required=False)
-        self.assertEqual(left == right, False)
-        self.assertEqual(left != right, True)
-
-    def test___eq___same_type_same_attrs(self):
-        left = self._makeOne()
-        right = self._makeOne()
-        self.assertEqual(left == right, True)
-        self.assertEqual(left != right, False)
-
     def test_get_miss(self):
         field = self._makeOne(__name__='nonesuch')
         inst = DummyInst()
@@ -364,44 +424,14 @@ def test_set_hit(self):
         field.set(inst, 'AFTER')
         self.assertEqual(inst.extant, 'AFTER')
 
-    def test_is_hashable(self):
-        field = self._makeOne()
-        hash(field)  # doesn't raise
 
-    def test_equal_instances_have_same_hash(self):
-        # Equal objects should have equal hashes
-        field1 = self._makeOne()
-        field2 = self._makeOne()
-        self.assertIsNot(field1, field2)
-        self.assertEqual(field1, field2)
-        self.assertEqual(hash(field1), hash(field2))
-
-    def test_hash_across_unequal_instances(self):
-        # Hash equality does not imply equal objects.
-        # Our implementation only considers property names,
-        # not values. That's OK, a dict still does the right thing.
-        field1 = self._makeOne(title=u'foo')
-        field2 = self._makeOne(title=u'bar')
-        self.assertIsNot(field1, field2)
-        self.assertNotEqual(field1, field2)
-        self.assertEqual(hash(field1), hash(field2))
-
-        d = {field1: 42}
-        self.assertIn(field1, d)
-        self.assertEqual(42, d[field1])
-        self.assertNotIn(field2, d)
-        with self.assertRaises(KeyError):
-            d[field2]
-
-class ContainerTests(unittest.TestCase):
+class ContainerTests(EqualityTestsMixin,
+                     unittest.TestCase):
 
     def _getTargetClass(self):
         from zope.schema._bootstrapfields import Container
         return Container
 
-    def _makeOne(self, *args, **kw):
-        return self._getTargetClass()(*args, **kw)
-
     def test_validate_not_required(self):
         field = self._makeOne(required=False)
         field.validate(None)
@@ -529,15 +559,13 @@ def test_validate_too_long(self):
         self.assertRaises(TooLong, mml._validate, (0, 1, 2))
 
 
-class TextTests(unittest.TestCase):
+class TextTests(EqualityTestsMixin,
+                unittest.TestCase):
 
     def _getTargetClass(self):
         from zope.schema._bootstrapfields import Text
         return Text
 
-    def _makeOne(self, *args, **kw):
-        return self._getTargetClass()(*args, **kw)
-
     def test_ctor_defaults(self):
         from zope.schema._compat import text_type
         txt = self._makeOne()
@@ -593,15 +621,13 @@ def test_fromUnicode_hit(self):
         self.assertEqual(txt.fromUnicode(deadbeef), deadbeef)
 
 
-class TextLineTests(unittest.TestCase):
+class TextLineTests(EqualityTestsMixin,
+                    unittest.TestCase):
 
     def _getTargetClass(self):
         from zope.schema._field import TextLine
         return TextLine
 
-    def _makeOne(self, *args, **kw):
-        return self._getTargetClass()(*args, **kw)
-
     def test_class_conforms_to_ITextLine(self):
         from zope.interface.verify import verifyClass
         from zope.schema.interfaces import ITextLine
@@ -711,15 +737,13 @@ def test_constraint(self):
         self.assertEqual(field.constraint(u'abc\ndef'), False)
 
 
-class BoolTests(unittest.TestCase):
+class BoolTests(EqualityTestsMixin,
+                unittest.TestCase):
 
     def _getTargetClass(self):
         from zope.schema._bootstrapfields import Bool
         return Bool
 
-    def _makeOne(self, *args, **kw):
-        return self._getTargetClass()(*args, **kw)
-
     def test_ctor_defaults(self):
         txt = self._makeOne()
         self.assertEqual(txt._type, bool)
@@ -774,16 +798,14 @@ def test_missing_value_no_min_or_max(self):
         self.assertEqual(self.mvm_missing_value, field.missing_value)
 
 
-class IntTests(OrderableMissingValueMixin,
+class IntTests(EqualityTestsMixin,
+               OrderableMissingValueMixin,
                unittest.TestCase):
 
     def _getTargetClass(self):
         from zope.schema._bootstrapfields import Int
         return Int
 
-    def _makeOne(self, *args, **kw):
-        return self._getTargetClass()(*args, **kw)
-
     def test_ctor_defaults(self):
         from zope.schema._compat import integer_types
         txt = self._makeOne()