Fixed #27431 -- Prevented disabled form fields from appearing as changed.

django/forms/fields.py

@@ -187,6 +187,10 @@ class Field(object):
         """
         Return True if data differs from initial.
         """
+        # Always return False if the field is disabled since self.bound_data
+        # always uses the initial value in this case.
+        if self.disabled:
+            return False
         try:
             data = self.to_python(data)
             if hasattr(self, '_coerce'):

tests/forms_tests/field_tests/test_base.py

@@ -34,3 +34,9 @@ class BasicFieldsTests(SimpleTestCase):
         f.fields['field2'].choices = [('2', '2')]
         self.assertEqual(f.fields['field1'].widget.choices, [('1', '1')])
         self.assertEqual(f.fields['field2'].widget.choices, [('2', '2')])
+
+
+class DisabledFieldTests(SimpleTestCase):
+    def test_disabled_field_has_changed_always_false(self):
+        disabled_field = Field(disabled=True)
+        self.assertFalse(disabled_field.has_changed('x', 'y'))