[augeas-devel] need help with learning lense grammar

[Joshua Hoblitt]

I've never really tried to use Augeas before yesterday and I've been
unable to find lenses for the /etc/auto.master and autofs(5) config
files, so I decided to try to write my own.

I've looked at the step by step directions and eventually simplified
things by using pre-existing lenses as examples.
http://augeas.net/page/Creating_a_lens_step_by_step

As a first stab at automaster(5), this is what I've come up with,
although it's not complete:

    module Automaster =
        autoload xfm

        let eol     = Util.eol
        let comment = Util.comment
        let empty   = Util.empty
        let comma   = Sep.comma
        let colon   = Sep.colon
        let sep_spc = Sep.space

        let word       = /[^,:#\n\t ]+/

        let record = [ seq "automap" .
    			[ label "key" . store word ] . sep_spc .
    			( [ label "map-type" . store word ] . comma )? .
    			( [ label "format" . store word ] . colon )? .
    			( [ label "map" . store word ] . sep_spc )? .
    			( [ label "options" . store word ] . sep_spc )?
    		 ] (* removed eol as I think sep_spc will consume \n *

        let lns = ( empty | comment | record ) *

        let filter = incl "/etc/auto.master"

        let xfm = transform lns filter

There is an error in this grammar in the whitespace handling but it's
not jump out at me.
The error message:

    $ augtool --version
    augtool 0.9.0 <http://augeas.net/>
    Copyright (C) 2009-2010 David Lutterkort
    License LGPLv2+: GNU LGPL version 2.1 or later
                     <http://www.gnu.org/licenses/lgpl-2.1.html>
    This is free software: you are free to change and redistribute it.
    There is NO WARRANTY, to the extent permitted by law.

    Written by David Lutterkort
    $ augparse automaster.aug
    Syntax error in lens definition
    automaster.aug:16.4-22.4:Failed to compile record
    automaster.aug:16.19-21.71:exception: ambiguous concatenation
          First regexp: /(([^,:#=\n\t ]+))([ \t]+)(((([^,:#=\n\t
]+))(,))?)(((([^,:#=\n\t ]+))(:))?)(((([^,:#=\n\t ]+))([ \t]+))?)/
          Second regexp: /((([^,:#=\n\t ]+))([ \t]+))?/
          'A A ' can be split into
          'A |=|A '

         and
          'A A |=|'

        First lens: automaster.aug:16.19-20.67:
        Second lens: automaster.aug:21.24-.71:


So it appears that /[ ]/ can consume a newline in this regex dialect?
What is the proper way to structure this grammar so that whitespace
handling isn't ambiguous?

Thanks,

-Josh

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