[1.6.x] Fixed #22245 -- Avoided widget overwrite in forms.IntegerField subclasses

Thanks Jeroen Pulles for the report and Simon Charette for the review.
Backport of 5a976b4bec from master.

django/forms/fields.py

@@ -216,13 +216,16 @@ class CharField(Field):
 
 
 class IntegerField(Field):
+    widget = NumberInput
     default_error_messages = {
         'invalid': _('Enter a whole number.'),
     }
 
     def __init__(self, max_value=None, min_value=None, *args, **kwargs):
         self.max_value, self.min_value = max_value, min_value
-        kwargs.setdefault('widget', NumberInput if not kwargs.get('localize') else self.widget)
+        if kwargs.get('localize') and self.widget == NumberInput:
+            # Localized number input is not well supported on most browsers
+            kwargs.setdefault('widget', super(IntegerField, self).widget)
         super(IntegerField, self).__init__(*args, **kwargs)
 
         if max_value is not None:

docs/releases/1.6.3.txt

@@ -18,3 +18,8 @@ several bugs in 1.6.2:
 * Fixed crash of ``QuerySet``\s that use ``F() + timedelta()`` when their query
   was compiled more once
   (`#21643 <http://code.djangoproject.com/ticket/21643>`_).
+
+* Prevented custom ``widget`` class attribute of
+  :class:`~django.forms.IntegerField` subclasses from being overwritten by the
+  code in their ``__init__`` method
+  (`#22245 <http://code.djangoproject.com/ticket/22245>`_).

tests/forms_tests/tests/test_fields.py

@@ -234,6 +234,18 @@ class FieldsTests(SimpleTestCase):
         f1 = IntegerField(localize=True)
         self.assertWidgetRendersTo(f1, '<input id="id_f" name="f" type="text" />')
 
+    def test_integerfield_subclass(self):
+        """
+        Test that class-defined widget is not overwritten by __init__ (#22245).
+        """
+        class MyIntegerField(IntegerField):
+            widget = Textarea
+
+        f = MyIntegerField()
+        self.assertEqual(f.widget.__class__, Textarea)
+        f = MyIntegerField(localize=True)
+        self.assertEqual(f.widget.__class__, Textarea)
+
     # FloatField ##################################################################
 
     def test_floatfield_1(self):