Colin Watson has proposed merging ~cjwatson/launchpad:py3-pgsession-datetime-compatibility into launchpad:master.
Commit message: Handle unpickling of Python 2 datetime objects on Python 3 Requested reviews: Launchpad code reviewers (launchpad-reviewers) For more details, see: https://code.launchpad.net/~cjwatson/launchpad/+git/launchpad/+merge/399133 Some of the pickled objects in the session database are `datetime.datetime` objects (`logintime` and `last_write`). There are particular difficulties with unpickling these objects on various Python 3 versions, as described in https://bugs.python.org/issue22005. Work around these using a customized unpickler. -- Your team Launchpad code reviewers is requested to review the proposed merge of ~cjwatson/launchpad:py3-pgsession-datetime-compatibility into launchpad:master.
diff --git a/lib/lp/services/webapp/pgsession.py b/lib/lp/services/webapp/pgsession.py index 3f035d3..0a5c664 100644 --- a/lib/lp/services/webapp/pgsession.py +++ b/lib/lp/services/webapp/pgsession.py @@ -6,7 +6,9 @@ __metaclass__ = type from collections import MutableMapping +from datetime import datetime import hashlib +import io import time from lazr.restful.utils import get_current_browser_request @@ -30,6 +32,35 @@ HOURS = 60 * MINUTES DAYS = 24 * HOURS +if six.PY3: + class Python2FriendlyUnpickler(pickle._Unpickler): + """An unpickler that handles Python 2 datetime objects. + + Python 3 versions before 3.6 fail to unpickle Python 2 datetime + objects (https://bugs.python.org/issue22005); even in Python >= 3.6 + they require passing a different encoding to pickle.loads, which may + have undesirable effects on other objects being unpickled. Work + around this by instead patching in a different encoding just for the + argument to datetime.datetime. + """ + + def find_class(self, module, name): + if module == 'datetime' and name == 'datetime': + original_encoding = self.encoding + self.encoding = 'bytes' + + def datetime_factory(pickle_data): + self.encoding = original_encoding + return datetime(pickle_data) + + return datetime_factory + else: + return super(Python2FriendlyUnpickler, self).find_class( + module, name) +else: + Python2FriendlyUnpickler = pickle.Unpickler + + class PGSessionBase: store_name = 'session' @@ -186,7 +217,8 @@ class PGSessionPkgData(MutableMapping, PGSessionBase): result = self.store.execute( query, (self.session_data.hashed_client_id, self.product_id)) for key, pickled_value in result: - value = pickle.loads(bytes(pickled_value)) + value = Python2FriendlyUnpickler( + io.BytesIO(bytes(pickled_value))).load() self._data_cache[key] = value def __getitem__(self, key): diff --git a/lib/lp/services/webapp/tests/test_pgsession.py b/lib/lp/services/webapp/tests/test_pgsession.py index 971ad4c..4d033fd 100644 --- a/lib/lp/services/webapp/tests/test_pgsession.py +++ b/lib/lp/services/webapp/tests/test_pgsession.py @@ -5,6 +5,7 @@ __metaclass__ = type +from datetime import datetime import hashlib from zope.publisher.browser import TestRequest @@ -167,3 +168,43 @@ class TestPgSession(TestCase): # also see the page test xx-no-anonymous-session-cookies for tests of # the cookie behaviour. + + def test_datetime_compatibility(self): + # datetime objects serialized by either Python 2 or 3 can be + # unserialized as part of the session. + client_id = u'Client Id #1' + product_id = u'Product Id' + expected_datetime = datetime(2021, 3, 4, 0, 50, 1, 300000) + + session = self.sdc[client_id] + session._ensureClientId() + + # These are returned by the following code in Python 2.7 and 3.5 + # respectively: + # + # pickle.dumps(expected_datetime, protocol=2) + python_2_pickle = ( + b'\x80\x02cdatetime\ndatetime\nq\x00' + b'U\n\x07\xe5\x03\x04\x002\x01\x04\x93\xe0q\x01\x85q\x02Rq\x03.') + python_3_pickle = ( + b'\x80\x02cdatetime\ndatetime\nq\x00' + b'c_codecs\nencode\nq\x01' + b'X\r\x00\x00\x00\x07\xc3\xa5\x03\x04\x002\x01\x04\xc2\x93\xc3\xa0' + b'q\x02X\x06\x00\x00\x00latin1q\x03\x86q\x04Rq\x05\x85q\x06R' + b'q\x07.') + + store = self.sdc.store + store.execute( + "SELECT set_session_pkg_data(?, ?, ?, ?)", + (session.hashed_client_id, product_id, u'logintime', + python_2_pickle), + noresult=True) + store.execute( + "SELECT set_session_pkg_data(?, ?, ?, ?)", + (session.hashed_client_id, product_id, u'last_write', + python_3_pickle), + noresult=True) + + pkgdata = session[product_id] + self.assertEqual(expected_datetime, pkgdata['logintime']) + self.assertEqual(expected_datetime, pkgdata['last_write'])
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