bpo-29931 fix __lt__ check in ipaddress.ip_interface for both v4 and v6. (#879)

the original logic was just comparing the network address
but this is wrong because if the network address is equal then
we need to compare the ip address for breaking the tie

add more ip_interface comparison tests

Lib/ipaddress.py

@@ -1410,7 +1410,8 @@ class IPv4Interface(IPv4Address):
         if address_less is NotImplemented:
             return NotImplemented
         try:
-            return self.network < other.network
+            return (self.network < other.network or
+                    self.network == other.network and address_less)
         except AttributeError:
             # We *do* allow addresses and interfaces to be sorted. The
             # unassociated address is considered less than all interfaces.
@@ -2100,7 +2101,8 @@ class IPv6Interface(IPv6Address):
         if address_less is NotImplemented:
             return NotImplemented
         try:
-            return self.network < other.network
+            return (self.network < other.network or
+                    self.network == other.network and address_less)
         except AttributeError:
             # We *do* allow addresses and interfaces to be sorted. The
             # unassociated address is considered less than all interfaces.

Lib/test/test_ipaddress.py

@@ -1405,14 +1405,35 @@ class IpaddrUnitTest(unittest.TestCase):
                         ipaddress.ip_address('::2'))
 
     def testInterfaceComparison(self):
-        self.assertTrue(ipaddress.ip_interface('1.1.1.1') <=
-                        ipaddress.ip_interface('1.1.1.1'))
-        self.assertTrue(ipaddress.ip_interface('1.1.1.1') <=
-                        ipaddress.ip_interface('1.1.1.2'))
-        self.assertTrue(ipaddress.ip_interface('::1') <=
-                        ipaddress.ip_interface('::1'))
-        self.assertTrue(ipaddress.ip_interface('::1') <=
-                        ipaddress.ip_interface('::2'))
+        self.assertTrue(ipaddress.ip_interface('1.1.1.1/24') ==
+                        ipaddress.ip_interface('1.1.1.1/24'))
+        self.assertTrue(ipaddress.ip_interface('1.1.1.1/16') <
+                        ipaddress.ip_interface('1.1.1.1/24'))
+        self.assertTrue(ipaddress.ip_interface('1.1.1.1/24') <
+                        ipaddress.ip_interface('1.1.1.2/24'))
+        self.assertTrue(ipaddress.ip_interface('1.1.1.2/16') <
+                        ipaddress.ip_interface('1.1.1.1/24'))
+        self.assertTrue(ipaddress.ip_interface('1.1.1.1/24') >
+                        ipaddress.ip_interface('1.1.1.1/16'))
+        self.assertTrue(ipaddress.ip_interface('1.1.1.2/24') >
+                        ipaddress.ip_interface('1.1.1.1/24'))
+        self.assertTrue(ipaddress.ip_interface('1.1.1.1/24') >
+                        ipaddress.ip_interface('1.1.1.2/16'))
+
+        self.assertTrue(ipaddress.ip_interface('::1/64') ==
+                        ipaddress.ip_interface('::1/64'))
+        self.assertTrue(ipaddress.ip_interface('::1/64') <
+                        ipaddress.ip_interface('::1/80'))
+        self.assertTrue(ipaddress.ip_interface('::1/64') <
+                        ipaddress.ip_interface('::2/64'))
+        self.assertTrue(ipaddress.ip_interface('::2/48') <
+                        ipaddress.ip_interface('::1/64'))
+        self.assertTrue(ipaddress.ip_interface('::1/80') >
+                        ipaddress.ip_interface('::1/64'))
+        self.assertTrue(ipaddress.ip_interface('::2/64') >
+                        ipaddress.ip_interface('::1/64'))
+        self.assertTrue(ipaddress.ip_interface('::1/64') >
+                        ipaddress.ip_interface('::2/48'))
 
     def testNetworkComparison(self):
         # ip1 and ip2 have the same network address

Misc/NEWS

@@ -301,6 +301,9 @@ Extension Modules
 Library
 -------
 
+- bpo-29931: Fixed comparison check for ipaddress.ip_interface objects.
+  Patch by Sanjay Sundaresan.
+
 - bpo-29953: Fixed memory leaks in the replace() method of datetime and time
   objects when pass out of bound fold argument.