Get system user id in a lazy manner

Calling getpass.getuser may lead to breakage in environments where there
is no entries in the /etc/passwd file for the current user.

Setting the environment variables for the git user configurations should
prevents GitPython from using values from /etc/passwd. However, doing so
will not prevent reading /etc/passwd and looking for an entry with the
current user UID.

This patch changes the behavior described above so GitPython will
perform a lazy evaluation of /etc/passwd, only doing so when the
environment variables for the git user configuration are not available.

Signed-off-by: Athos Ribeiro <athos@redhat.com>

2 files changed, 36 insertions, 5 deletions

diff --git a/git/util.py b/git/util.py
index 216703cb..44eb0e51 100644
--- a/git/util.py
+++ b/git/util.py
@@ -582,8 +582,16 @@ class Actor(object):
     @classmethod
     def _main_actor(cls, env_name, env_email, config_reader=None):
         actor = Actor('', '')
-        default_email = get_user_id()
-        default_name = default_email.split('@')[0]
+        user_id = None  # We use this to avoid multiple calls to getpass.getuser()
+
+        def default_email():
+            nonlocal user_id
+            if not user_id:
+                user_id = get_user_id()
+            return user_id
+
+        def default_name():
+            default_email().split('@')[0]
 
         for attr, evar, cvar, default in (('name', env_name, cls.conf_name, default_name),
                                           ('email', env_email, cls.conf_email, default_email)):
@@ -592,10 +600,10 @@ class Actor(object):
                 setattr(actor, attr, val)
             except KeyError:
                 if config_reader is not None:
-                    setattr(actor, attr, config_reader.get_value('user', cvar, default))
+                    setattr(actor, attr, config_reader.get_value('user', cvar, default()))
                 # END config-reader handling
                 if not getattr(actor, attr):
-                    setattr(actor, attr, default)
+                    setattr(actor, attr, default())
             # END handle name
         # END for each item to retrieve
         return actor
diff --git a/test/test_util.py b/test/test_util.py
index df4e5474..2f946891 100644
--- a/test/test_util.py
+++ b/test/test_util.py
@@ -4,10 +4,11 @@
 # This module is part of GitPython and is released under
 # the BSD License: http://www.opensource.org/licenses/bsd-license.php
 
+import os
 import pickle
 import tempfile
 import time
-from unittest import skipIf
+from unittest import mock, skipIf
 from datetime import datetime
 
 import ddt
@@ -215,6 +216,28 @@ class TestUtils(TestBase):
             self.assertIsInstance(Actor.author(cr), Actor)
         # END assure config reader is handled
 
+    @mock.patch("getpass.getuser")
+    def test_actor_get_uid_laziness_not_called(self, mock_get_uid):
+        env = {
+            "GIT_AUTHOR_NAME": "John Doe",
+            "GIT_AUTHOR_EMAIL": "jdoe@example.com",
+            "GIT_COMMITTER_NAME": "Jane Doe",
+            "GIT_COMMITTER_EMAIL": "jane@example.com",
+        }
+        os.environ.update(env)
+        for cr in (None, self.rorepo.config_reader()):
+            Actor.committer(cr)
+            Actor.author(cr)
+        self.assertFalse(mock_get_uid.called)
+
+    @mock.patch("getpass.getuser")
+    def test_actor_get_uid_laziness_called(self, mock_get_uid):
+        for cr in (None, self.rorepo.config_reader()):
+            Actor.committer(cr)
+            Actor.author(cr)
+        self.assertTrue(mock_get_uid.called)
+        self.assertEqual(mock_get_uid.call_count, 4)
+
     def test_actor_from_string(self):
         self.assertEqual(Actor._from_string("name"), Actor("name", None))
         self.assertEqual(Actor._from_string("name <>"), Actor("name", ""))