X509Name: Use functools.totalordering for comparisons (#1086)

* X509Name: Use functools.totalordering for comparisons

- Reduce the magic
- Make it more readable
- Make it easier to add type annotations in the future

* Correctly return NotImplemented

* Add new comparison test case

Author: lovetox

src/OpenSSL/crypto.py

@@ -1,9 +1,8 @@
 import calendar
 import datetime
-
 from base64 import b16encode
+import functools
 from functools import partial
-from operator import __eq__, __ne__, __lt__, __le__, __gt__, __ge__
 
 from cryptography import utils, x509
 from cryptography.hazmat.primitives.asymmetric import dsa, rsa
@@ -528,6 +527,7 @@ def get_elliptic_curve(name):
     raise ValueError("unknown curve name", name)
 
 
+@functools.total_ordering
 class X509Name:
     """
     An X.509 Distinguished Name.
@@ -642,23 +642,17 @@ def __getattr__(self, name):
             _lib.OPENSSL_free(result_buffer[0])
         return result
 
-    def _cmp(op):
-        def f(self, other):
-            if not isinstance(other, X509Name):
-                return NotImplemented
-            result = _lib.X509_NAME_cmp(self._name, other._name)
-            return op(result, 0)
-
-        return f
+    def __eq__(self, other):
+        if not isinstance(other, X509Name):
+            return NotImplemented
 
-    __eq__ = _cmp(__eq__)
-    __ne__ = _cmp(__ne__)
+        return _lib.X509_NAME_cmp(self._name, other._name) == 0
 
-    __lt__ = _cmp(__lt__)
-    __le__ = _cmp(__le__)
+    def __lt__(self, other):
+        if not isinstance(other, X509Name):
+            return NotImplemented
 
-    __gt__ = _cmp(__gt__)
-    __ge__ = _cmp(__ge__)
+        return _lib.X509_NAME_cmp(self._name, other._name) < 0
 
     def __repr__(self):
         """

tests/test_crypto.py

@@ -1398,6 +1398,19 @@ def assert_greater_than(a, b):
         # other X509Name.
         assert_greater_than(x509_name(CN="def"), x509_name(CN="abc"))
 
+        def assert_raises(a, b):
+            with pytest.raises(TypeError):
+                a < b
+            with pytest.raises(TypeError):
+                a <= b
+            with pytest.raises(TypeError):
+                a > b
+            with pytest.raises(TypeError):
+                a >= b
+
+        # Only X509Name objects can be compared with lesser than / greater than
+        assert_raises(x509_name(), object())
+
     def test_hash(self):
         """
         `X509Name.hash` returns an integer hash based on the value of the name.