Fixed #22838 -- Deprecated ModelChoiceField.cache_choices.

Undocumented, untested and probably not even useful feature.

django/forms/models.py

@@ -6,6 +6,7 @@ and database field objects.
 from __future__ import unicode_literals
 
 from collections import OrderedDict
+import warnings
 
 from django.core.exceptions import (
     ImproperlyConfigured, ValidationError, NON_FIELD_ERRORS, FieldError)
@@ -16,6 +17,7 @@ from django.forms.utils import ErrorList
 from django.forms.widgets import (SelectMultiple, HiddenInput,
     MultipleHiddenInput)
 from django.utils import six
+from django.utils.deprecation import RemovedInDjango19Warning
 from django.utils.encoding import smart_text, force_text
 from django.utils.text import get_text_list, capfirst
 from django.utils.translation import ugettext_lazy as _, ugettext
@@ -1092,7 +1094,7 @@ class ModelChoiceField(ChoiceField):
                             ' the available choices.'),
     }
 
-    def __init__(self, queryset, empty_label="---------", cache_choices=False,
+    def __init__(self, queryset, empty_label="---------", cache_choices=None,
                  required=True, widget=None, label=None, initial=None,
                  help_text='', to_field_name=None, limit_choices_to=None,
                  *args, **kwargs):
@@ -1100,6 +1102,12 @@ class ModelChoiceField(ChoiceField):
             self.empty_label = None
         else:
             self.empty_label = empty_label
+        if cache_choices is not None:
+            warnings.warn("cache_choices has been deprecated and will be "
+                "removed in Django 1.9.",
+                RemovedInDjango19Warning, stacklevel=2)
+        else:
+            cache_choices = False
         self.cache_choices = cache_choices
 
         # Call Field instead of ChoiceField __init__() because we don't need
@@ -1191,7 +1199,7 @@ class ModelMultipleChoiceField(ModelChoiceField):
         'invalid_pk_value': _('"%(pk)s" is not a valid value for a primary key.')
     }
 
-    def __init__(self, queryset, cache_choices=False, required=True,
+    def __init__(self, queryset, cache_choices=None, required=True,
                  widget=None, label=None, initial=None,
                  help_text='', *args, **kwargs):
         super(ModelMultipleChoiceField, self).__init__(queryset, None,