[gerrit_utils] Add caching to ShouldUseSSO

This only lasts per process invocation, so we don't worry about cache
size (and it's a minor performance save).

Bug: b/350806563
Change-Id: Ie8e1aa2933c5582a3a2e2f75f04590f6bb432c4c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5833280
Commit-Queue: Allen Li <ayatane@chromium.org>
Reviewed-by: Josip Sokcevic <sokcevic@chromium.org>

gerrit_util.py

@@ -11,6 +11,7 @@ from __future__ import annotations
 
 import base64
 import contextlib
+import functools
 import http.cookiejar
 import json
 import logging
@@ -173,6 +174,7 @@ class SSOHelper(object):
 ssoHelper = SSOHelper()
 
 
+@functools.lru_cache(maxsize=None)
 def ShouldUseSSO(host: str, email: str) -> bool:
     """Return True if we should use SSO for the given Gerrit host and user."""
     LOGGER.debug("Determining whether we should use SSO...")

tests/gerrit_util_test.py

@@ -731,17 +731,15 @@ class ShouldUseSSOTest(unittest.TestCase):
     def setUp(self) -> None:
         self.newauth = mock.patch('newauth.Enabled', return_value=True)
         self.newauth.start()
-
         self.cwd = mock.patch('os.getcwd', return_value='/fake/cwd')
         self.cwd.start()
-
         self.sso = mock.patch('gerrit_util.ssoHelper.find_cmd',
                               return_value='/fake/git-remote-sso')
         self.sso.start()
-
         scm_mock.GIT(self)
-
         self.addCleanup(mock.patch.stopall)
+
+        gerrit_util.ShouldUseSSO.cache_clear()
         return super().setUp()
 
     def tearDown(self) -> None: