Implement __eq__ for validators (#8925)

* Implement equality operator and add test coverage

* Add documentation on implementation

docs/api-guide/validators.md

@@ -53,7 +53,7 @@ If we open up the Django shell using `manage.py shell` we can now
 
 The interesting bit here is the `reference` field. We can see that the uniqueness constraint is being explicitly enforced by a validator on the serializer field.
 
-Because of this more explicit style REST framework includes a few validator classes that are not available in core Django. These classes are detailed below.
+Because of this more explicit style REST framework includes a few validator classes that are not available in core Django. These classes are detailed below.  REST framework validators, like their Django counterparts, implement the `__eq__` method, allowing you to compare instances for equality.
 
 ---
 

rest_framework/validators.py

@@ -79,6 +79,15 @@ class UniqueValidator:
             smart_repr(self.queryset)
         )
 
+    def __eq__(self, other):
+        if not isinstance(other, self.__class__):
+            return NotImplemented
+        return (self.message == other.message
+                and self.requires_context == other.requires_context
+                and self.queryset == other.queryset
+                and self.lookup == other.lookup
+                )
+
 
 class UniqueTogetherValidator:
     """
@@ -166,6 +175,16 @@ class UniqueTogetherValidator:
             smart_repr(self.fields)
         )
 
+    def __eq__(self, other):
+        if not isinstance(other, self.__class__):
+            return NotImplemented
+        return (self.message == other.message
+                and self.requires_context == other.requires_context
+                and self.missing_message == other.missing_message
+                and self.queryset == other.queryset
+                and self.fields == other.fields
+                )
+
 
 class ProhibitSurrogateCharactersValidator:
     message = _('Surrogate characters are not allowed: U+{code_point:X}.')
@@ -177,6 +196,13 @@ class ProhibitSurrogateCharactersValidator:
             message = self.message.format(code_point=ord(surrogate_character))
             raise ValidationError(message, code=self.code)
 
+    def __eq__(self, other):
+        if not isinstance(other, self.__class__):
+            return NotImplemented
+        return (self.message == other.message
+                and self.code == other.code
+                )
+
 
 class BaseUniqueForValidator:
     message = None
@@ -230,6 +256,17 @@ class BaseUniqueForValidator:
                 self.field: message
             }, code='unique')
 
+    def __eq__(self, other):
+        if not isinstance(other, self.__class__):
+            return NotImplemented
+        return (self.message == other.message
+                and self.missing_message == other.missing_message
+                and self.requires_context == other.requires_context
+                and self.queryset == other.queryset
+                and self.field == other.field
+                and self.date_field == other.date_field
+                )
+
     def __repr__(self):
         return '<%s(queryset=%s, field=%s, date_field=%s)>' % (
             self.__class__.__name__,

tests/test_validators.py

@@ -1,4 +1,5 @@
 import datetime
+from unittest.mock import MagicMock
 
 import pytest
 from django.db import DataError, models
@@ -787,3 +788,13 @@ class ValidatorsTests(TestCase):
             validator.filter_queryset(
                 attrs=None, queryset=None, field_name='', date_field_name=''
             )
+
+    def test_equality_operator(self):
+        mock_queryset = MagicMock()
+        validator = BaseUniqueForValidator(queryset=mock_queryset, field='foo',
+                                           date_field='bar')
+        validator2 = BaseUniqueForValidator(queryset=mock_queryset, field='foo',
+                                            date_field='bar')
+        assert validator == validator2
+        validator2.date_field = "bar2"
+        assert validator != validator2