[issue17204] argparser's subparsers.add_parser() should accept an ArgumentParser

[paul j3]

paul j3 added the comment:

In the attached patch I modified 'add_parser' to take a 'parser' keyword 
parameter.  If given, it is used as the parser, rather than create a new one.  
Thus an existing parser, or one created with a custom ArgumentParser class, 
could be used as a subparser.  

In this sample script, a parent parser is used as subparser in 2 different ways 
- via the parent mechanism, and with this new add_parser parameter.

parent = argparse.ArgumentParser()
parent.add_argument('-f')
parent.add_argument('bar')

parser = argparse.ArgumentParser()
sp = parser.add_subparsers(dest='cmd')
p1 = sp.add_parser('cmd1', add_help=False, parents=[parent])
p2 = sp.add_parser('cmd2', parser=parent)
parent.add_argument('test')
assert p2 is parent
assert p1 is not parent
print(parser.parse_args())

This change passes existing unittests.  I don't think there are any backward 
compatibility issues.

--
keywords: +patch
Added file: http://bugs.python.org/file36858/patch0.diff

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[issue17204] argparser's subparsers.add_parser() should accept an ArgumentParser

[Mickaël Falck]

Changes by Mickaël Falck lastmi...@gmail.com:


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[issue17204] argparser's subparsers.add_parser() should accept an ArgumentParser

[paul j3]

paul j3 added the comment:

http://stackoverflow.com/a/20167038/901925
is an example of using `_parser_class` to produce different behavior in the 
subparsers.

parser = ArgumentParser()
parser.add_argument('foo')
sp = parser.add_subparsers(dest='cmd')
sp._parser_class = SubParser # use different parser class for subparsers
spp1 = sp.add_parser('cmd1')
spp1.add_argument('-x')
spp1.add_argument('bar')
spp1.add_argument('vars',nargs='*')

In this case the SubParser class implements a `parse_intermixed_known_args` 
method that handles that `nargs='*'` argument.

http://bugs.python.org/issue14191

It shouldn't be hard to add `parser_class` as a documented optional argument to 
`add_subparsers`.

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[issue17204] argparser's subparsers.add_parser() should accept an ArgumentParser

[paul j3]

paul j3 added the comment:

The 'subparsers' object has a _parser_class attribute that is normally set to 
the class of the parent parser.  In the attached file I create a

class CustomParser(argparse.ArgumentParser)

that makes a parser instance which copies all of the attributes of prototype 
parser.

proto1 = argparse.ArgumentParser(prog='SUBPROG1')
proto1.add_argument('--foo')
subparsers._parser_class = CustomParser
sub1 = subparsers.add_parser('cmd1', proto=proto1, help='parser based on 
proto1')

'sub1' is a functional copy of 'proto1'.  I think this does what you want 
without changing the argparse code.  There probably is a way of defining 
CustomParser (maybe its '__new__' method) so 'sub1' is actually 'proto1'.  But 
the copy approach appears to work just fine.

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Added file: http://bugs.python.org/file29916/issue17204.py

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[issue17204] argparser's subparsers.add_parser() should accept an ArgumentParser

[Greg Trahair]

Changes by Greg Trahair greg.trah...@gmail.com:


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[issue17204] argparser's subparsers.add_parser() should accept an ArgumentParser

[Greg Trahair]

Changes by Greg Trahair greg.trah...@gmail.com:


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[issue17204] argparser's subparsers.add_parser() should accept an ArgumentParser

[Chris Jerdonek]

New submission from Chris Jerdonek:

Currently, argparser's subparsers.add_parser() method (for adding sub-commands) 
takes the following input:

This object has a single method, add_parser(), which takes a command name and 
any ArgumentParser constructor arguments, and returns an ArgumentParser object 
that can be modified as usual.

(from 
http://docs.python.org/dev/library/argparse.html#argparse.ArgumentParser.add_subparsers
 )

It would be nice if one could also pass an ArgumentParser object to 
add_parser().  This would allow the composition of parsers.  For example, if a 
library exposed an ArgumentParser command-line API, one could expose that 
library's commands as a sub-command of the parent project's command-line API 
using add_parser().

--
components: Library (Lib)
messages: 182081
nosy: bethard, chris.jerdonek
priority: normal
severity: normal
stage: needs patch
status: open
title: argparser's subparsers.add_parser() should accept an ArgumentParser
type: enhancement
versions: Python 3.4

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