"Type" parameter not functioning as expected

[nodeca]

"Type" parameter not functioning as expected

[puzrin]

At least, test works :) https://github.com/nodeca/argparse/blob/master/test/optionals.js#L522

Could you provide minimalistic executable example, that show your problem?

[hpaulj]

With this argument specification, I get the following:

> args=p.parseArgs([])
{ port: 4723 }
> typeof args.port
'number'
> args=p.parseArgs(['-p','23'])
{ port: [ 23 ] }
> typeof args.port
'object'

In other words, while the default is a number, the result with an value is an array containing a number.

To get the desired behavior, leave off the nargs, or use nargs: null. The default behavior is to accept one argument, converting it with the specified type function. (Same is true in the Python original)

type:'number' does not work because no 'number' type has been registered. Using this produces an error in the addArgument call. This code follows the Python in providing 'int' and 'float' types, which use parseInt and parserFloat respectively (both of which return a javascript number).

Also required:false is unnecessary. An optional argument is by default, not required.

help:'Port to listen on (default: %(defaultValue)s)' will insert your default value in the help string. argparse ignores your example argument.

[hpaulj]

Once it is understood that nargs=n means, return an array of length n, this behavior makes sense. However we might be able to make this situation more user friendly. Maybe it's just a matter of making the documentation clearer. Or we could issue a warning if nargs:1 is used. A defaultValue: [23] implies the user understands what nargs=1 means, but defaultValue: 23 suggests that they do not.

But do we have a working 'warning' system? Node.js console.warn() doesn't do much more than console.log.

Also, I wonder if this issue has ever been raised for the Python code. There are several cases in test_argparse.py for nargs=1, some for the basic use, some for combinations with other nargs.

[puzrin]

#48 . 2 troubles with wrong params combination - that becomes a system problem :)

Probably, doc should be improved.

[hpaulj]

Python 2.7.3 argparse documentation
http://docs.python.org/2/library/argparse.html#nargs

15.4.3.3. nargs
ArgumentParser objects usually associate a single command-line argument with a single action to be taken. The nargs keyword argument associates a different number of command-line arguments with a single action. The supported values are:

N (an integer). N arguments from the command line will be gathered together into a list. For example:

>>>
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', nargs=2)
>>> parser.add_argument('bar', nargs=1)
>>> parser.parse_args('c --foo a b'.split())
Namespace(bar=['c'], foo=['a', 'b'])
Note that nargs=1 produces a list of one item. This is different from the default, in which the item is produced by itself.

[puzrin]

Ah, nothing to improve. Even better :)

[jlipps]

great! didn't realize that nargs: 1 meant a list of length one, and no nargs meant a single value. slightly unintuitive. my case works now.