From 615bc95976ca0dba4ce8d77b06d19205d1fe7a08 Mon Sep 17 00:00:00 2001
From: Ross McFarland <ross@github.com>
Date: Fri, 23 Jun 2017 09:49:25 -0700
Subject: [PATCH] CNAME cannot coexist with other records on a node

---
 octodns/zone.py            | 18 +++++++++++++++---
 tests/test_octodns_zone.py | 27 ++++++++++++++++++++++++++-
 2 files changed, 41 insertions(+), 4 deletions(-)

diff --git a/octodns/zone.py b/octodns/zone.py
index 1822fec..03bc41c 100644
--- a/octodns/zone.py
+++ b/octodns/zone.py
@@ -19,6 +19,10 @@ class DuplicateRecordException(Exception):
     pass
 
 
+class InvalidNodeException(Exception):
+    pass
+
+
 def _is_eligible(record):
     # Should this record be considered when computing changes
     # We ignore all top-level NS records
@@ -59,9 +63,17 @@ class Zone(object):
                 raise SubzoneRecordException('Record {} a managed sub-zone '
                                              'and not of type NS'
                                              .format(record.fqdn))
-        if record in self.records:
-            raise DuplicateRecordException('Duplicate record {}, type {}'
-                                           .format(record.fqdn, record._type))
+        for existing in self.records:
+            if record == existing:
+                raise DuplicateRecordException('Duplicate record {}, type {}'
+                                               .format(record.fqdn,
+                                                       record._type))
+            elif name == existing.name and (record._type == 'CNAME' or
+                                            existing._type == 'CNAME'):
+                raise InvalidNodeException('Invalid state, CNAME at {} '
+                                           'cannot coexist with other records'
+                                           .format(record.fqdn))
+
         self.records.add(record)
 
     def changes(self, desired, target):
diff --git a/tests/test_octodns_zone.py b/tests/test_octodns_zone.py
index 88bbb68..a4d7300 100644
--- a/tests/test_octodns_zone.py
+++ b/tests/test_octodns_zone.py
@@ -8,7 +8,8 @@ from __future__ import absolute_import, division, print_function, \
 from unittest import TestCase
 
 from octodns.record import ARecord, AaaaRecord, Create, Delete, Record, Update
-from octodns.zone import DuplicateRecordException, SubzoneRecordException, Zone
+from octodns.zone import DuplicateRecordException, InvalidNodeException, \
+    SubzoneRecordException, Zone
 
 from helpers import SimpleProvider
 
@@ -205,3 +206,27 @@ class TestZone(TestCase):
 
         self.assertTrue(zone_missing.changes(zone_normal, provider))
         self.assertFalse(zone_missing.changes(zone_ignored, provider))
+
+    def test_cname_coexisting(self):
+        zone = Zone('unit.tests.', [])
+        a = Record.new(zone, 'www', {
+            'ttl': 60,
+            'type': 'A',
+            'value': '9.9.9.9',
+        })
+        cname = Record.new(zone, 'www', {
+            'ttl': 60,
+            'type': 'CNAME',
+            'value': 'foo.bar.com.',
+        })
+
+        # add cname to a
+        zone.add_record(a)
+        with self.assertRaises(InvalidNodeException):
+            zone.add_record(cname)
+
+        # add a to cname
+        zone = Zone('unit.tests.', [])
+        zone.add_record(cname)
+        with self.assertRaises(InvalidNodeException):
+            zone.add_record(a)