Re: Filter with arguments

[John MacFarlane <jgm-TVLZxgkOlNX2fBVCVOL8/A@public.gmane.org>]

+++ Joost Kremers [Jan 06 17 13:27 ]:
>
>On Fri, Jan 06 2017, John MacFarlane wrote:
>>This is a pretty common request.  A couple of complications:
>>
>>1.  Pandoc calls each filter with one argument, the name of
>>the output format.  (Filters thus have access to this.)
>>If we allowed `-F "pantable -t csv"`, how would this work?
>>Would pandoc call `pantable latex -t csv`?  Would the filter
>>be expecting this?
>
>For a properly written filter that shouldn't be a problem, should it? 
>You just need to decide on one way of doing it and stick to it. 
>Filters then need to be updated accordingly. Or are you worried about 
>backward compatibility?

Well, I'm anticipating people getting confused.  "I said to
run --filter 'myfilter myarg', and for some reason 'myarg'
isn't the first argument!"

What's wrong with communicating options to filters through
environment variables, which you can already do?

    PANTABLE_OUTPUT="csv" pandoc --filter pantable

>pandoc --filter "My Cool Filter.py" --filter-args "-t csv"
>
>with each --filter-args referring to the immediately preceding 
>--filters option. Depending on how Pandoc calls filters, it may even 
>be possible to just pass it the literal string argument of 
>--filter-args without having to parse it into different options.

I think this is too complex, with --filter-args affecting
the immediately preceding --filter option.

Again, I'd have to be convinced that environment variables
don't already provide a perfectly adequate way to do this.