allow to override field config_type and set custom additional fields

constance/admin.py

@@ -15,6 +15,7 @@ from django.template.context import RequestContext
 from django.utils import six
 from django.utils.formats import localize
 from django.utils.translation import ugettext_lazy as _
+import django
 
 try:
     from django.utils.encoding import smart_bytes
@@ -51,6 +52,17 @@ FIELDS = {
     float: (fields.FloatField, {'widget': NUMERIC_WIDGET}),
 }
 
+def parse_additional_fields(fields):
+   for key in fields:
+      field = fields[key]
+      field[0] = eval(field[0])
+      if 'widget' in field[1]:
+         field[1]['widget'] = eval(field[1]['widget'])
+   return fields
+
+
+FIELDS.update(parse_additional_fields(settings.ADDITIONAL_FIELDS))
+
 if not six.PY3:
     FIELDS.update({
         long: INTEGER_LIKE,
@@ -65,8 +77,13 @@ class ConstanceForm(forms.Form):
         super(ConstanceForm, self).__init__(*args, initial=initial, **kwargs)
         version_hash = hashlib.md5()
 
-        for name, (default, help_text) in settings.CONFIG.items():
-            config_type = type(default)
+        for name, options in settings.CONFIG.items():
+            default, help_text = options[0], options[1]
+            if len(options) == 3:
+               config_type = options[2]
+            else:
+               config_type = type(default)
+
             if config_type not in FIELDS:
                 raise ImproperlyConfigured(_("Constance doesn't support "
                                              "config values of the type "
@@ -111,8 +128,8 @@ class ConstanceAdmin(admin.ModelAdmin):
         # First load a mapping between config name and default value
         if not self.has_change_permission(request, None):
             raise PermissionDenied
-        default_initial = ((name, default)
-            for name, (default, help_text) in settings.CONFIG.items())
+        default_initial = ((name, options[0])
+            for name, options in settings.CONFIG.items())
         # Then update the mapping with actually values from the backend
         initial = dict(default_initial,
             **dict(config._backend.mget(settings.CONFIG.keys())))
@@ -136,7 +153,8 @@ class ConstanceAdmin(admin.ModelAdmin):
             'form': form,
             'media': self.media + form.media,
         }
-        for name, (default, help_text) in settings.CONFIG.items():
+        for name, options in settings.CONFIG.items():
+            default, help_text = options[0], options[1]
             # First try to load the value from the actual backend
             value = initial.get(name)
             # Then if the returned value is None, get the default

constance/base.py

@@ -11,7 +11,9 @@ class Config(object):
 
     def __getattr__(self, key):
         try:
-            default, help_text = settings.CONFIG[key]
+            if not len(settings.CONFIG[key]) in (2, 3):
+                raise AttributeError(key)
+            default = settings.CONFIG[key][0]
         except KeyError:
             raise AttributeError(key)
         result = self._backend.get(key)

constance/settings.py

@@ -5,6 +5,8 @@ BACKEND = getattr(settings, 'CONSTANCE_BACKEND',
 
 CONFIG = getattr(settings, 'CONSTANCE_CONFIG', {})
 
+ADDITIONAL_FIELDS = getattr(settings, 'CONSTANCE_ADDITIONAL_FIELDS', {})
+
 DATABASE_CACHE_BACKEND = getattr(settings, 'CONSTANCE_DATABASE_CACHE_BACKEND',
                                  None)
 

docs/index.rst

@@ -53,6 +53,33 @@ admin will show.
 See the :ref:`Backends <backends>` section how to setup the backend and
 finish the configuration.
 
+Custom fields
+-------------
+
+You can set the field type by the third value in the `CONSTANCE_CONFIG`
+tuple. The value can be string or one of the supported types:
+
+.. code-block:: python
+        'THE_ANSWER': (42, 'Answer to the Ultimate Question of Life, '
+                                   'The Universe, and Everything', str),
+
+If you can add your custom field types, you can use the
+`CONSTANCE_ADDITIONAL_FIELDS` variable. Note that you must
+use later evaluated strings instead of direct classes:
+
+.. code-block:: python
+        CONSTANCE_ADDITIONAL_FIELDS = {
+           'yes_no_null_select': ['django.forms.fields.ChoiceField',
+              {
+              'widget': 'django.forms.Select',
+              'choices': (("-----", None), ("yes", "Yes"), ("no", "No"))
+              }],
+        }
+
+       CONSTANCE_CONFIG = {
+           'MY_SELECT_KEY': ('yes', 'select yes or no', 'yes_no_null_select'),
+       }
+
 Usage
 -----