Add a validator to models CharField that should be regular expressions

cas_server/models.py

@@ -466,7 +466,8 @@ class ServicePattern(models.Model):
             "A regular expression matching services. "
             "Will usually looks like '^https://some\\.server\\.com/path/.*$'."
             "As it is a regular expression, special character must be escaped with a '\\'."
-        )
+        ),
+        validators=[utils.regexpr_validator]
     )
     #: Name of the attribute to transmit as username, if empty the user login is used
     user_field = models.CharField(
@@ -660,7 +661,8 @@ class FilterAttributValue(models.Model):
     pattern = models.CharField(
         max_length=255,
         verbose_name=_(u"pattern"),
-        help_text=_(u"a regular expression")
+        help_text=_(u"a regular expression"),
+        validators=[utils.regexpr_validator]
     )
     #: ForeignKey to a :class:`ServicePattern`. :class:`FilterAttributValue` instances for a
     #: :class:`ServicePattern` are accessible thought its :attr:`ServicePattern.filters`
@@ -689,7 +691,8 @@ class ReplaceAttributValue(models.Model):
     pattern = models.CharField(
         max_length=255,
         verbose_name=_(u"pattern"),
-        help_text=_(u"An regular expression maching whats need to be replaced")
+        help_text=_(u"An regular expression maching whats need to be replaced"),
+        validators=[utils.regexpr_validator]
     )
     #: The replacement to what is mached by :attr:`pattern`. groups are capture by \\1, \\2 …
     replace = models.CharField(

cas_server/tests/test_utils.py

@@ -255,3 +255,9 @@ class UtilsTestCase(TestCase):
                 self.assertIsInstance(result, dict)
                 self.assertIn('applied', result)
                 self.assertIsInstance(result['applied'], datetime.datetime)
+
+    def test_regexpr_validator(self):
+        """test the function regexpr_validator"""
+        utils.regexpr_validator("^a$")
+        with self.assertRaises(utils.ValidationError):
+            utils.regexpr_validator("[")

cas_server/utils.py

@@ -18,7 +18,10 @@ from django.contrib import messages
 from django.contrib.messages import constants as DEFAULT_MESSAGE_LEVELS
 from django.core.serializers.json import DjangoJSONEncoder
 from django.utils import timezone
+from django.core.exceptions import ValidationError
+from django.utils.translation import ugettext_lazy as _
 
+import re
 import random
 import string
 import json
@@ -700,3 +703,19 @@ def logout_request(ticket):
         'datetime': timezone.now().isoformat(),
         'ticket':  ticket
     }
+
+
+def regexpr_validator(value):
+    """
+        Test that ``value`` is a valid regular expression
+
+        :param unicode value: A regular expression to test
+        :raises ValidationError: if ``value`` is not a valid regular expression
+    """
+    try:
+        re.compile(value)
+    except re.error:
+        raise ValidationError(
+            _('"%(value)s" is not a valid regular expression'),
+            params={'value': value}
+        )