datetime.time issue with pickling in PyPy

[scaramallion]

BPO	41966
Nosy	@abalkin, @serhiy-storchaka, @pganssle, @miss-islington, @scaramallion
PRs	bpo-41966: Fix pickling pure datetime.time subclasses #22731 [3.9] bpo-41966: Fix pickling pure datetime.time subclasses (GH-22731) #22747 [3.8] bpo-41966: Fix pickling pure datetime.time subclasses (GH-22731) #22748

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2020-10-18.16:00:16.227>
created_at = <Date 2020-10-07.10:08:31.925>
labels = ['3.8', 'type-bug', 'library', '3.9', '3.10']
title = 'datetime.time issue with pickling in PyPy'
updated_at = <Date 2020-10-18.16:00:16.227>
user = 'https://github.com/scaramallion'

bugs.python.org fields:

activity = <Date 2020-10-18.16:00:16.227>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = True
closed_date = <Date 2020-10-18.16:00:16.227>
closer = 'serhiy.storchaka'
components = ['Library (Lib)']
creation = <Date 2020-10-07.10:08:31.925>
creator = 'ddddaaaa'
dependencies = []
files = []
hgrepos = []
issue_num = 41966
keywords = ['patch']
message_count = 5.0
messages = ['378155', '378214', '378871', '378874', '378875']
nosy_count = 5.0
nosy_names = ['belopolsky', 'serhiy.storchaka', 'p-ganssle', 'miss-islington', 'ddddaaaa']
pr_nums = ['22731', '22747', '22748']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue41966'
versions = ['Python 3.8', 'Python 3.9', 'Python 3.10']

[scaramallion]

I've run into an issue pickling a datetime.time subclass in PyPy3. I believe it arises because PyPy uses the pure Python implementation of time and time.__reduce_ex__() returns (time, ...) on this line (

cpython/Lib/datetime.py

Line 1551 in 044a104

return (time, self._getstate(protocol))

) rather than (self.__class__, ...) as it does for datetime.datetime (and in datetime.date.__reduce__()). So when pickle creates the dump it uses the time class rather than my subclass.

[scaramallion]

Code demonstrating the issue; the CTimeFoo class is pickled correctly, but TimeFoo isn't.

import builtins
from _datetime import time as ctime

original_importer = builtins.__import__

def my_importer(name, globals, locals, fromlist, level):
    if name == '_datetime':
        raise ImportError

    return original_importer(name, globals, locals, fromlist, level)

builtins.__import__ = my_importer

import datetime

builtins.__import__ = original_importer

import pickle


class CTimeFoo(ctime): pass
class TimeFoo(datetime.time): pass
class DateFoo(datetime.date): pass


if __name__ == "__main__":
    t = DateFoo(2001, 2, 3) 
    d = pickle.dumps(t)  # OK
    print(d)
    # b'\x80\x04\x95#\x00\x00\x00\x00\x00\x00\x00\x8c\x08__main__\x94\x8c\x07DateFoo\x94\x93\x94C\x04\x07\xd1\x02\x03\x94\x85\x94R\x94.'
    t = pickle.loads(d)

    t = CTimeFoo(1, 2, 3)  
    d = pickle.dumps(t)  # OK
    print(d)
    # b'\x80\x04\x95&\x00\x00\x00\x00\x00\x00\x00\x8c\x08__main__\x94\x8c\x08CTimeFoo\x94\x93\x94C\x06\x01\x02\x03\x00\x00\x00\x94\x85\x94R\x94.'
    t = pickle.loads(d)

    t = TimeFoo(1, 2, 3)
    d = pickle.dumps(t)  # :(
    print(d)
    # b'\x80\x04\x95"\x00\x00\x00\x00\x00\x00\x00\x8c\x08datetime\x94\x8c\x04time\x94\x93\x94C\x06\x01\x02\x03\x00\x00\x00\x94\x85\x94R\x94.'
    t = pickle.loads(d)