From b8353016b7d6a4046f4c30017987c2e75597285b Mon Sep 17 00:00:00 2001
From: Karen Tracey <kmtracey@gmail.com>
Date: Sun, 13 Nov 2011 15:09:08 +0000
Subject: [PATCH] Fixed #13640: Avoid generating an exception when a model has
 an attribute named 'evaluate'. Thanks LukaszKorzybski and tobias.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@17093 bcc190cf-cafb-0310-a4f2-bffc1f526a37
---
 django/db/models/sql/query.py                |  3 ++-
 tests/regressiontests/model_regress/tests.py | 15 +++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/django/db/models/sql/query.py b/django/db/models/sql/query.py
index 61fd2be40b..4afe28806d 100644
--- a/django/db/models/sql/query.py
+++ b/django/db/models/sql/query.py
@@ -14,6 +14,7 @@ from django.utils.encoding import force_unicode
 from django.utils.tree import Node
 from django.db import connections, DEFAULT_DB_ALIAS
 from django.db.models import signals
+from django.db.models.expressions import ExpressionNode
 from django.db.models.fields import FieldDoesNotExist
 from django.db.models.query_utils import InvalidQuery
 from django.db.models.sql import aggregates as base_aggregates_module
@@ -1064,7 +1065,7 @@ class Query(object):
             value = True
         elif callable(value):
             value = value()
-        elif hasattr(value, 'evaluate'):
+        elif isinstance(value, ExpressionNode):
             # If value is a query expression, evaluate it
             value = SQLEvaluator(value, self)
             having_clause = value.contains_aggregate
diff --git a/tests/regressiontests/model_regress/tests.py b/tests/regressiontests/model_regress/tests.py
index 07ad8faea1..77bb4f23eb 100644
--- a/tests/regressiontests/model_regress/tests.py
+++ b/tests/regressiontests/model_regress/tests.py
@@ -164,8 +164,23 @@ class ModelTests(TestCase):
             1
         )
 
+
 class ModelValidationTest(TestCase):
     def test_pk_validation(self):
         one = NonAutoPK.objects.create(name="one")
         again = NonAutoPK(name="one")
         self.assertRaises(ValidationError, again.validate_unique)
+
+
+class EvaluateMethodTest(TestCase):
+    """
+    Regression test for #13640: cannot filter by objects with 'evaluate' attr
+    """
+
+    def test_model_with_evaluate_method(self):
+        """
+        Ensures that you can filter by objects that have an 'evaluate' attr
+        """
+        dept = Department.objects.create(pk=1, name='abc')
+        dept.evaluate = 'abc'
+        Worker.objects.filter(department=dept)