I looked into changelog and the source code to see if the behavior was wanted but I was not able to see the source of the issue.

import argparse
parser = argparse.ArgumentParser(allow_abbrev=True)
parser.add_argument('-o', type=str, required=True, dest="bla", help="bla")
known_args, rest_of_args = parser.parse_known_args(["-o", "test1", "-object_lto", "test2"])
print(rest_of_args)

Executing with python 3.7.8

With allow_abbrev=True:

['test2']

allow_abbrev=False:

['-object_lto', 'test2']


Executed with python 3.8.5

With allow_abbrev=True:

['test2']

allow_abbrev=False:

['test2']


Is it expected? How do I get the behavior of python 3.7 in python 3.8?