Remove 'Hold down "Control" ...' message from help_text

When getting the help_text from a field where `many=True`, Django
appends 'Hold down "Control", or "Command" on a Mac, to select more than
one.' to the help_text. This makes some sense in Django's ModelForms,
but no sense in the API.

rest_framework/fields.py

@@ -100,6 +100,19 @@ def humanize_strptime(format_string):
     return format_string
 
 
+def strip_multiple_choice_msg(help_text):
+    """
+    Remove the 'Hold down "control" ...' message that is enforced in select
+    multiple fields.
+
+    See https://code.djangoproject.com/ticket/9321
+    """
+    multiple_choice_msg = _(' Hold down "Control", or "Command" on a Mac, to select more than one.')
+    multiple_choice_msg = unicode(multiple_choice_msg)
+
+    return help_text.replace(multiple_choice_msg, '')
+
+
 class Field(object):
     read_only = True
     creation_counter = 0
@@ -122,7 +135,7 @@ class Field(object):
             self.label = smart_text(label)
 
         if help_text is not None:
-            self.help_text = smart_text(help_text)
+            self.help_text = strip_multiple_choice_msg(smart_text(help_text))
 
     def initialize(self, parent, field_name):
         """

rest_framework/tests/models.py

@@ -52,7 +52,7 @@ class CallableDefaultValueModel(RESTFrameworkModel):
 
 
 class ManyToManyModel(RESTFrameworkModel):
-    rel = models.ManyToManyField(Anchor)
+    rel = models.ManyToManyField(Anchor, help_text='Some help text.')
 
 
 class ReadOnlyManyToManyModel(RESTFrameworkModel):

rest_framework/tests/test_serializer.py

@@ -1376,6 +1376,18 @@ class FieldLabelTest(TestCase):
         self.assertEqual('Label', relations.HyperlinkedRelatedField(view_name='fake', label='Label', help_text='Help', many=True).label)
 
 
+# Test for issue #961
+
+class ManyFieldHelpTextTest(TestCase):
+    def test_help_text_no_hold_down_control_msg(self):
+        """
+        Validate that help_text doesn't contain the 'Hold down "Control" ...'
+        message that Django appends to choice fields.
+        """
+        rel_field = fields.Field(help_text=ManyToManyModel._meta.get_field('rel').help_text)
+        self.assertEqual('Some help text.', unicode(rel_field.help_text))
+
+
 class AttributeMappingOnAutogeneratedFieldsTests(TestCase):
 
     def setUp(self):