Do not crash if there is no start_date (fix #108)

Though the clean_fields() method checks the start_date and is executed before
the clean() method, the ValidationError is caught and the clean() method is
called anyway. Hence, the clean() method can be called even if there is no
start_date.

This prevents a crash in the clean() method even if there is no start_date.

coin/members/models.py

@@ -428,7 +428,7 @@ class MembershipFee(models.Model):
                                     verbose_name='date du paiement')
 
     def clean(self):
-        if self.end_date is None:
+        if self.start_date is not None and self.end_date is None:
             self.end_date = self.start_date + datetime.timedelta(364)
 
     def __unicode__(self):

coin/members/tests.py

@@ -509,3 +509,22 @@ class TestValidators(TestCase):
         chatroom_url_validator('irc://irc.example.com/#chan')
         with self.assertRaises(ValidationError):
             chatroom_url_validator('http://#faimaison@irc.geeknode.org')
+
+
+class MembershipFeeTests(TestCase):
+    def test_mandatory_start_date(self):
+        member = Member(first_name='foo', last_name='foo', password='foo', email='foo')
+        member.save()
+
+        # If there is no start_date clean_fields() should raise an
+        # error but not clean().
+        membershipfee = MembershipFee(member=member)
+        self.assertRaises(ValidationError, membershipfee.clean_fields)
+        self.assertIsNone(membershipfee.clean())
+
+        # If there is a start_date, everything is fine.
+        membershipfee = MembershipFee(member=member, start_date=date.today())
+        self.assertIsNone(membershipfee.clean_fields())
+        self.assertIsNone(membershipfee.clean())
+
+        member.delete()