[New-bugs-announce] [issue39716] argparse.ArgumentParser does not raise on duplicated subparsers, even though it does on duplicated flags

[Antony Lee]

New submission from Antony Lee <anntzer.lee at gmail.com>:

If one tries to add twice the same flag to an ArgumentParser, one gets a helpful exception:

    from argparse import ArgumentParser
    p = ArgumentParser()
    p.add_argument("--foo")
    p.add_argument("--foo")

results in

    argparse.ArgumentError: argument --foo: conflicting option string: --foo

However, adding twice the same subparser raises no exception:

    from argparse import ArgumentParser
    p = ArgumentParser()
    sp = p.add_subparsers()
    sp.add_parser("foo")
    sp.add_parser("foo")

even though the two subparsers shadow one another in the same way as two identical flags.

----------
components: Library (Lib)
messages: 362421
nosy: Antony.Lee
priority: normal
severity: normal
status: open
title: argparse.ArgumentParser does not raise on duplicated subparsers, even though it does on duplicated flags
versions: Python 3.9

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue39716>
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