[issue9340] argparse parse_known_args does not work with subparsers

[Steven Bethard]

Steven Bethard  added the comment:

Fixed with a variant of Catherine's patch (following R. David Murray's 
suggestion of inlining the two methods) in r86111 (3.X) and r86112 (2.7). Also 
added one more test to make sure that the order of the extra arguments is 
consistent (extra arguments from main parser before extra arguments from 
subparser).

--
resolution:  -> fixed
stage: patch review -> committed/rejected
status: open -> closed
versions:  -Python 3.1

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[issue9340] argparse parse_known_args does not work with subparsers

[R. David Murray]

Changes by R. David Murray :


--
stage: needs patch -> patch review
versions: +Python 3.1 -Python 3.3

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[issue9340] argparse parse_known_args does not work with subparsers

[R. David Murray]

R. David Murray  added the comment:

I've looked over this patch, and it seems to me that there is no compelling 
reason to create two new functions.  I think it would be clearer to just inline 
that code in the places it is used.  If it turns out later that the code needs 
to be reused elsewhere, it can be factored out at that time.  (Also, as it 
stands the methods are being made part of the public API, and that doesn't look 
right to me.)

Catherine, if you'd like to update the patch that would be great.  Otherwise we 
will hopefully get to it during the upcoming bug weekend.

--
nosy: +r.david.murray

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[issue9340] argparse parse_known_args does not work with subparsers

[Guandalino]

Changes by Guandalino :


--
nosy: +guandalino

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[issue9340] argparse parse_known_args does not work with subparsers

[Catherine Devlin]

Catherine Devlin  added the comment:

This patch fixes it with a fourth approach: if unrecognized arguments are found 
during subparser parsing, information about them is inserted into the namespace 
(under "._unrecognized"), and the decision about whether to exit is deferred.  
When top-level parsing is finished, those recorded unrecognized args are added 
to whatever was found by the main parser.  

It passes the tests I submitted yesterday.

--
Added file: http://bugs.python.org/file18388/unrecognized_args_defer_exit.patch

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[issue9340] argparse parse_known_args does not work with subparsers

[Catherine Devlin]

Catherine Devlin  added the comment:

Some simple unit tests for parse_known_args on a parser with a subparser.  They 
are indeed failing on the trunk.

--
Added file: 
http://bugs.python.org/file18346/test_subparser_parse_known_args.patch

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[issue9340] argparse parse_known_args does not work with subparsers

[Catherine Devlin]

Changes by Catherine Devlin :


Removed file: 
http://bugs.python.org/file18344/test_subparser_parse_known_args.patch

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[issue9340] argparse parse_known_args does not work with subparsers

[Catherine Devlin]

Catherine Devlin  added the comment:

Some basic unit tests for parse_known_args on a subparser.

--
keywords: +patch
nosy: +catherine
Added file: 
http://bugs.python.org/file18344/test_subparser_parse_known_args.patch

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[issue9340] argparse parse_known_args does not work with subparsers

[Steven Bethard]

New submission from Steven Bethard :

[Moved from http://code.google.com/p/argparse/issues/detail?id=45]

If you try to use parse_known_args and you have a subparser, the subparser will 
still complain if it sees extra arguments:

>>> parser = argparse.ArgumentParser()
>>> subparsers = parser.add_subparsers()
>>> subparsers.add_parser('A')
>>> parser.parse_known_args(['A', '--foo', 'b'])
usage:  A [-h]
 A: error: unrecognized arguments: --foo b

What should be returned is probably:

>>> parser.parse_known_args(['A', '--foo', 'b'])
(Namespace(), ['--foo', 'b'])

The problem is that subparsers don't know whether they're being called by 
parse_args() or parse_known_args(). I see a few possible fixes:

* Add another argument to Action.__call__ that indicates what method is being 
called. But that would break any existing subclasses.

* Do some stack inspection using sys._getframe(). But that's not guaranteed to 
work on other implementations of Python.

* When parse_args is called, set some flag on the subparsers object that causes 
it to call parse_known_args instead, and restore that flag before 
parse_known_args returns. This probably introduces potential threading issues, 
though practically perhaps they'll never turn up.

--
assignee: bethard
components: Library (Lib)
messages: 111285
nosy: bethard
priority: normal
severity: normal
stage: needs patch
status: open
title: argparse parse_known_args does not work with subparsers
type: behavior
versions: Python 2.7, Python 3.2, Python 3.3

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