Can optparse do dependencies?

[Giovanni Bajo]

Raymond Hettinger wrote:

>> I'd like to setup command line switches that are dependent on other
>> switches, similar to what rpm does listed below. From the grammar
>> below we see that the "query-options" are dependent on the query
>> switch, {-q|--query}. Can "optparse" do this or do I have to code my
>> own "thing"? Thanks.
>>
>> QUERYING AND VERIFYING PACKAGES:
>>        rpm {-q|--query} [select-options] [query-options]
>> ...
>>    query-options
>>         [--changelog] [-c,--configfiles] [-d,--docfiles] [--dump]
>>         [--filesbypkg] [-i,--info] [--last] [-l,--list]
>>         [--provides] [--qf,--queryformat QUERYFMT]
>>         [-R,--requires] [--scripts] [-s,--state]
>>         [--triggers,--triggerscripts]
>
> The optparse module doesn't have native support for switch
> dependencies; however, it could likely be done with multiple passes.
> The parse_args() takes an args list as an argument.  Make first pass
> that captures your main query switches, then run another parser on a
> slice of the args list.
>
> For example, capture the main switches on a first pass over the full
> argument list (catching all possible main switches and treating
> everything else as a catchall).  Given, args=['-ql', '--changelog',
> '-d', '-c'], parse out the --changelog and then call another parser
> with args=['-d', '-c'].
>
> This functionality seems useful enough to build into the tool
> directly, so do consider putting a feature request on SourceForge
> (and assign to Greg Ward).

In fact, if we were to request an addition to optparse in this direction, I
think it should add standardized support for the "subcommand pattern", that is
the same command line arrangement that CVS, SVN and other programs uses. rpm
doesn't use it and I consider this an error in UI design (it should really have
been "rpm query --changelog" and similar).
-- 
Giovanni Bajo