Better display of objects of BasePermissionsField

- Permissions are grouped by content type and displayed under its
verbose_name_plural.
- Default permissions appear before custom ones.
- Use `permissions-field` class to enhance display.

kfet/auth/fields.py

@@ -1,7 +1,21 @@
+import re
+from itertools import groupby
+from operator import attrgetter
+
 from django import forms
+from django.utils.translation import ugettext_lazy as _
 
 from .models import Group, Permission
 
+DEFAULT_PERMS = ['view', 'add', 'change', 'delete']
+
+DEFAULT_PERMS_LABELS = {
+    'view': _("Voir"),
+    'add': _("Ajouter"),
+    'change': _("Modifier"),
+    'delete': _("Supprimer"),
+}
+
 
 class GroupsField(forms.ModelMultipleChoiceField):
     def __init__(self, **kwargs):
@@ -12,11 +26,49 @@ class GroupsField(forms.ModelMultipleChoiceField):
 
 class BasePermissionsField(forms.ModelMultipleChoiceField):
     def __init__(self, **kwargs):
-        kwargs.setdefault('widget', forms.CheckboxSelectMultiple)
+        kwargs.setdefault('widget', forms.CheckboxSelectMultiple(attrs={
+            'field_class': 'permissions-field',
+        }))
         super().__init__(**kwargs)
 
-    def label_from_instance(self, obj):
-        return obj.name
+        # Contain permissions grouped by `ContentType`. Used as choices for
+        # this field.
+        grouped_choices = []
+
+        for ct, perms in groupby(self.queryset, attrgetter('content_type')):
+            model_opts = ct.model_class()._meta
+            choices = []
+
+            # This helps for the default permissions, if they exists, to appear
+            # at the beginning of the permissions list and use custom labels.
+            reg_defaults_p = re.compile(
+                r'^(?P<p_type>({defaults}))_{model_name}$'
+                .format(
+                    defaults='|'.join(DEFAULT_PERMS),
+                    model_name=model_opts.model_name,
+                )
+            )
+            next_default_pos = 0
+
+            for p in perms:
+                match = reg_defaults_p.match(p.codename)
+                if match:
+                    # `p` is a default permission. Use shorter label and insert
+                    # after the last default permission seen in `choices`.
+                    p_type = match.group('p_type')
+                    choices.insert(
+                        next_default_pos,
+                        (p.id, DEFAULT_PERMS_LABELS[p_type])
+                    )
+                    next_default_pos += 1
+                else:
+                    # Non-default permissions. Use the permission description,
+                    # instead of its `__str__`.
+                    choices.append((p.id, p.name))
+
+            grouped_choices.append((model_opts.verbose_name_plural, choices))
+
+        self.choices = grouped_choices
 
 
 class CorePermissionsField(BasePermissionsField):