Re: Filter with arguments

[BPJ <bpj-J3H7GcXPSITLoDKTGw+V6w@public.gmane.org>]

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It would work but it would need to be `-F myfilter --filter-option
myfilter='-foo'` so that pandoc sends the right options to the right filter
when running multiple filters. I still think '-M myfilter_foo=bar` is not
only sufficient but better. What we need is a way to specify non-markdown
metadata, e.g. that values of keys beginning with an underscore are
non-markdown. That's no big deal though. Filters can convert their metadata
options to plain data themselves.

/bpj

fre 6 jan. 2017 kl. 19:43 skrev Matthew Pickering <
matthewtpickering-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>:

> Communicating arguments though env vars is very ad-hoc, an option
>
> "--filter-arguments" (like Joost suggests) which took a string and
>
> passed it to the filter when invoked would be sufficient.
>
>
>
> pandoc --filter myfilter --filter-options="--foo --baz --bar"
>
>
>
> results in pandoc calling
>
>
>
> myfilter csv --foo --baz --bar
>
>
>
> I investigated reimplementing pandoc-lit as a filter but it was not
>
> possible because the program has a lot of command line arguments you
>
> need to specify.
>
>
>
> The worry about passing the format as the first argument being
>
> confusing could be overcome by embedding more metadata into the JSON
>
> input.
>
>
>
> Matt
>
>
>
> On Fri, Jan 6, 2017 at 6:32 PM, BPJ <bpj-J3H7GcXPSITLoDKTGw+V6w@public.gmane.org> wrote:
>
> > The best way to pass options to filters is through metadata. That gets
>
> > considerably easier if the filter can use a function which converts a
>
> > structure of metadata objects into a plain data structure so that
> `MetsMap`s
>
> > get converted to plain associative arrays, `MetaList`s to plain arrays
> and
>
> > other `Meta` elements to plain strings or booleans. It is easy to write
> such
>
> > a function using existing walking and steingification functions.
>
> >
>
> > Once you get the hang of that you don't feel any need to pass custom
>
> > arguments to filters because it is so convenient to do filter config in
> the
>
> > document. A useful way to avoid a lot of metadata keys prefixed with
> filter
>
> > names is to have a single key equal to the filter name with a mapping as
>
> > value which contains the options for that filter. Nothing hinders you
> from
>
> > also checking environment variables if metadata options are undefined and
>
> > use hardcoded defaults only if the env vars are also undefined. I do so
>
> > often enough to have written a helper function.
>
> >
>
> > /bpj
>
> >
>
> > fre 6 jan. 2017 kl. 14:00 skrev 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.
>
> >>
>
> >>
>
> >>
>
> >> --
>
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