argparse.ArgumentParser silently swallows multiple -- (double dash)

[Nikratio]

Consider this:

import argparse
p = argparse.ArgumentParser()
p.add_argument('arg1', type=str)
p.add_argument('args', nargs='*')
p.parse_args(['foo', '--', '--bar', '--', 'com'])

The semantics of -- are to not attempt to parse the remaining command line options as parameters. Therefore, the expected output is:

Namespace(arg1='foo', args=['--bar', '--', 'com'])

However, the actual output is:

Namespace(arg1='foo', args=['--bar', 'com'])

In other words, the second -- has silently been dropped.

Interestingly enough, if the arg1 parameter is dropped, this works correctly:

p = argparse.ArgumentParser()
p.add_argument('args', nargs='*')
p.parse_args(['foo', '--', '--bar', '--', 'com'])
--> Namespace(args=['foo', '--bar', '--', 'com'])

Linked PRs

• GH-95468: Prevent argparse from removing -- in cases where used to delineate positional args #124145
• gh-81691: Fix handling of multiple "--" (double dashes) in argparse #124233
• gh-95468: Add more tests for "--" (double dash) in test_argparse #124274
• [3.12] gh-95468: Add more tests for "--" (double dash) in test_argparse (GH-124274) #124276
• [3.13] gh-95468: Add more tests for "--" (double dash) in test_argparse (GH-124274) #125068

[serhiy-storchaka]

This is a duplicate of #81691.