Re: Filter with arguments

[Joost Kremers <joostkremers-97jfqw80gc6171pxa8y+qA@public.gmane.org>]

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?

> 2.  We'd get a quoted argument like `"pantable -t csv"` as a
> single string from the environment.  So pandoc would have to
> do its own parsing of this string into a command, options and
> arguments.  This is tricky.  Maybe some people are already
> using filters with spaces in them, like `-F "My Cool Filter.py".
> This kind of thing would break if pandoc assumed that the
> command was "My" and "Cool" an argument.

Perhaps the way to overcome this problem is to introduce another 
option, e.g., --filter-args, so you'd get:

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.



-- 
Joost Kremers
Life has its moments