simplify runtime code

Author: picnixz

Lib/smtplib.py

@@ -45,7 +45,6 @@
 import email.utils
 import email.message
 import email.generator
-import functools
 import base64
 import hmac
 import copy
@@ -179,19 +178,12 @@ def _fix_eols(data):
     return  re.sub(r'(?:\r\n|\n|\r(?!\n))', CRLF, data)
 
 
-# Use unbounded LRU cache instead of global variable to ease mocking.
-@functools.cache
-def _have_cram_md5_support():
-    """Check if CRAM-MD5 is supported by the host.
-
-    Note that CRAM-MD5 may be supported by the server
-    but not by the client if HMAC-MD5 is not supported.
-    """
-    try:
-        hmac.digest(b'', b'', 'md5')
-        return True
-    except ValueError:
-        return False
+try:
+    hmac.digest(b'', b'', 'md5')
+except ValueError:
+    _have_cram_md5_support = False
+else:
+    _have_cram_md5_support = True
 
 
 try:
@@ -682,7 +674,7 @@ def auth_cram_md5(self, challenge=None):
         # CRAM-MD5 does not support initial-response.
         if challenge is None:
             return None
-        if not _have_cram_md5_support():
+        if not _have_cram_md5_support:
             raise SMTPException("CRAM-MD5 is not supported")
         password = self.password.encode('ascii')
         authcode = hmac.HMAC(password, challenge, 'md5')
@@ -738,7 +730,7 @@ def login(self, user, password, *, initial_response_ok=True):
         advertised_authlist = self.esmtp_features["auth"].split()
 
         # Authentication methods we can handle in our preferred order:
-        if _have_cram_md5_support():
+        if _have_cram_md5_support:
             preferred_auths = ['CRAM-MD5', 'PLAIN', 'LOGIN']
         else:
             preferred_auths = ['PLAIN', 'LOGIN']

Lib/test/test_smtplib.py

@@ -17,6 +17,7 @@
 import threading
 
 import unittest
+import unittest.mock as mock
 from test import support, mock_socket
 from test.support import hashlib_helper
 from test.support import socket_helper
@@ -1034,7 +1035,6 @@ def handle_error(self):
 class SMTPSimTests(unittest.TestCase):
 
     def setUp(self):
-        smtplib._have_cram_md5_support.cache_clear()
         self.thread_key = threading_helper.threading_setup()
         self.real_getfqdn = socket.getfqdn
         socket.getfqdn = mock_socket.getfqdn
@@ -1186,6 +1186,7 @@ def testAUTH_CRAM_MD5(self):
         smtp.close()
 
     @hashlib_helper.block_algorithm('md5')
+    @mock.patch("smtplib._have_cram_md5_support", False)
     def testAUTH_CRAM_MD5_blocked(self):
         # CRAM-MD5 is the only "known" method by the server,
         # but it is not supported by the client. In particular,
@@ -1199,6 +1200,7 @@ def testAUTH_CRAM_MD5_blocked(self):
             smtp.login(sim_auth[0], sim_auth[1])
 
     @hashlib_helper.block_algorithm('md5')
+    @mock.patch("smtplib._have_cram_md5_support", False)
     def testAUTH_CRAM_MD5_blocked_and_fallback(self):
         # Test that PLAIN is tried after CRAM-MD5 failed
         self.serv.add_feature("AUTH CRAM-MD5 PLAIN")