Improve IPv6 validation

fixes #107

tests/test_ipv6.py

@@ -5,8 +5,10 @@
 
 
 @pytest.mark.parametrize(('address',), [
+    ('::',),
     ('::1',),
-    ('dead:beef:0:0:0:0:42:1',),
+    ('1::',),
+    ('dead:beef:0:0:0:0000:42:1',),
     ('abcd:ef::42:1',),
     ('0:0:0:0:0:ffff:1.2.3.4',),
     ('::192.168.30.2',),
@@ -21,6 +23,15 @@ def test_returns_true_on_valid_ipv6_address(address):
     ('abcd:1234::123::1',),
     ('1:2:3:4:5:6:7:8:9',),
     ('abcd::1ffff',),
+    ('1111:',),
+    (':8888',),
+    (':1.2.3.4',),
+    ('18:05',),
+    (':',),
+    (':1:2:',),
+    (':1:2::',),
+    ('::1:2::',),
+    ('8::1:2::9',),
 ])
 def test_returns_failed_validation_on_invalid_ipv6_address(address):
     assert isinstance(ipv6(address), ValidationFailure)

validators/ip_address.py

@@ -1,3 +1,5 @@
+from operator import xor
+
 from .utils import validator
 
 
@@ -57,7 +59,7 @@ def ipv4_cidr(value):
 @validator
 def ipv6(value):
     """
-    Return whether or not given value is a valid IP version 6 address
+    Return whether a given value is a valid IP version 6 address
     (including IPv4-mapped IPv6 addresses).
 
     This validator is based on `WTForms IPAddress validator`_.
@@ -112,9 +114,13 @@ def ipv6(value):
             if not 0 <= num <= 65536:
                 return False
 
-    if count_blank < 2:
+    if count_blank == 0 and len(ipv6_groups) == max_groups:
+        return True
+    elif count_blank == 1 and ipv6_groups[-1] and ipv6_groups[0]:
+        return True
+    elif count_blank == 2 and ((ipv6_groups[0] and not ipv6_groups[-1]) or (not ipv6_groups[0] and ipv6_groups[-1])):
         return True
-    elif count_blank == 2 and not ipv6_groups[0] and not ipv6_groups[1]:
+    elif count_blank == 3 and len(ipv6_groups) == 3:
         return True
     return False