Make OAuth2Session picklable (oauthlib #849)

HISTORY.rst

@@ -1,6 +1,14 @@
 History
 -------
 
+Unreleased
+++++++++++
+
+- ``OAuth2Session`` is picklable again: the internal no-op ``auth`` handler is
+  a module-level function instead of a lambda, so sessions can be used in a
+  ``multiprocessing`` context. Fixes `oauthlib #849
+  <https://github.com/oauthlib/oauthlib/issues/849>`_.
+
 v2.0.0 (22 March 2024)
 ++++++++++++++++++++++++
 

requests_oauthlib/oauth2_session.py

@@ -9,6 +9,17 @@
 log = logging.getLogger(__name__)
 
 
+def _no_op_auth(request):
+    """A no-op ``requests`` auth handler that returns the request unchanged.
+
+    ``requests`` calls ``auth(request)`` and uses the returned request, so this
+    prevents any automatic auth (e.g. from ``.netrc``); see GH #278. It is
+    defined at module level rather than as a lambda so that ``OAuth2Session``
+    instances remain picklable (GH #849).
+    """
+    return request
+
+
 class TokenUpdated(Warning):
     def __init__(self, token):
         super(TokenUpdated, self).__init__()
@@ -91,7 +102,7 @@ def __init__(
 
         # Ensure that requests doesn't do any automatic auth. See #278.
         # The default behavior can be re-enabled by setting auth to None.
-        self.auth = lambda r: r
+        self.auth = _no_op_auth
 
         # Allow customizations for non compliant providers through various
         # hooks to adjust requests and responses.

tests/test_oauth2_session.py

@@ -1,4 +1,5 @@
 import json
+import pickle
 import time
 import tempfile
 import shutil
@@ -59,6 +60,19 @@ def setUp(self):
         ]
         self.all_clients = self.clients + [self.client_MobileApplication]
 
+    def test_pickle(self):
+        # OAuth2Session must be picklable so it can be used in a
+        # multiprocessing context; a lambda in __init__ used to break this
+        # with "Can't pickle local object ...<lambda>" (#849).
+        for client in self.all_clients:
+            sess = OAuth2Session(client=client, token=self.token)
+            restored = pickle.loads(pickle.dumps(sess))
+            self.assertIsInstance(restored, OAuth2Session)
+            # The no-op auth handler must survive pickling and still return
+            # the request unchanged (disabling requests' automatic auth).
+            request = mock.sentinel.request
+            self.assertIs(restored.auth(request), request)
+
     def test_add_token(self):
         token = "Bearer " + self.token["access_token"]