Merge pull request #708 from requests-cache/sliced-pickles

Explicitly disable pickling CachedSession objects

3 files changed, 31 insertions, 3 deletions

diff --git a/HISTORY.md b/HISTORY.md
index b3ba499..d4a03bb 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -92,8 +92,12 @@
 * Fix usage of memory backend with `install_cache()`
 * Fix issue on Windows with occasional missing `CachedResponse.created_at` timestamp
 * Add `CachedRequest.path_url` property for compatibility with `RequestEncodingMixin`
-* Add compatibility with cattrs 22.1+
 * Fix potential `AttributeError` due to undetected imports when requests-cache is bundled in a PyInstaller package
+* Fix `AttributeError` when attempting to unpickle a `CachedSession` object, and instead disable
+  pickling by raising a `NotImplementedError`
+* Add compatibility with cattrs 22.1+
+* Fix forwarding connection parameters passed to `RedisCache` for redis-py 4.2 and python <=3.8
+* Fix forwarding connection parameters passed to `MongoCache` for pymongo 4.1 and python <=3.8
 
 **Dependencies:**
 * Replace `appdirs` with `platformdirs`
@@ -129,15 +133,27 @@ If you encounter a problem not listed here after updating to 1.0, please create
 * Internal utility module changes:
     * The `cache_control` module (added in `0.7`) has been split up into multiple modules in a new `policy` subpackage
 
-### 0.9.6 (2022-08-24)
+## 0.9.7 (Unreleased)
+Backport fixes from 1.0:
+* Fix potential `AttributeError` due to undetected imports when requests-cache is bundled in a PyInstaller package
+* Fix `AttributeError` when attempting to unpickle a `CachedSession` object, and instead disable
+  pickling by raising a `NotImplementedError`
+* Update to cattrs 22.2
+
+## 0.9.6 (2022-08-24)
+Backport fixes from 1.0:
 * Remove potentially problematic row count from `BaseCache.__str__()`
 * Remove upper version constraints for all non-dev dependencies
 * Make dependency specification consistent between PyPI and Conda-Forge packages
 
 ### 0.9.5 (2022-06-29)
-* Backport bugfixes from 1.0
+Backport fixes from 1.0:
+* Fix usage of memory backend with `install_cache()`
+* Add `CachedRequest.path_url` property
+* Add compatibility with cattrs 22.1
 
 ### 0.9.4 (2022-04-22)
+Backport fixes from 1.0:
 * Fix forwarding connection parameters passed to `RedisCache` for redis-py 4.2 and python <=3.8
 * Fix forwarding connection parameters passed to `MongoCache` for pymongo 4.1 and python <=3.8
 
diff --git a/requests_cache/session.py b/requests_cache/session.py
index e58cc57..3dbdb05 100644
--- a/requests_cache/session.py
+++ b/requests_cache/session.py
@@ -311,6 +311,12 @@ class CacheMixin(MIXIN_BASE):
         """**Deprecated:** Use ``session.cache.remove(expired=True)`` instead"""
         self.cache.delete(expired=True, invalid=True)
 
+    def __getstate__(self):
+        # Unlike requests.Session, CachedSession may contain backend connection objects that can't
+        # be pickled. Support for this could be added if necessary, but for now it's explicitly
+        # disabled to avoid confusing errors upon unpickling.
+        raise NotImplementedError('CachedSession cannot be pickled')
+
     def __repr__(self):
         return f'<CachedSession(cache={repr(self.cache)}, settings={self.settings})>'
 
diff --git a/tests/unit/test_session.py b/tests/unit/test_session.py
index 53e368c..60e8bb4 100644
--- a/tests/unit/test_session.py
+++ b/tests/unit/test_session.py
@@ -1,5 +1,6 @@
 """CachedSession tests that use mocked responses only"""
 import json
+import pickle
 from collections import UserDict, defaultdict
 from datetime import datetime, timedelta
 from logging import getLogger
@@ -76,6 +77,11 @@ def test_repr(mock_session):
     assert 'cache_control=True' in repr(mock_session)
 
 
+def test_pickle__disabled():
+    with pytest.raises(NotImplementedError):
+        pickle.dumps(CachedSession(backend='memory'))
+
+
 def test_response_defaults(mock_session):
     """Both cached and new responses should always have the following attributes"""
     mock_session.settings.expire_after = datetime.utcnow() + timedelta(days=1)