[augeas-devel] Non-empty string from get has turned into empty node for put direction - why?

Mon Dec 21 11:51:30 UTC 2015

Hi Raphael,

thank you for your quick response.

> The `mapping` lens has no label (…)

You're right, changing the lns definition to something like…

[ label "mapping" . dn . sp . (fqan . sp)? . login . eol ]

fixed most of the issues. Lens 'fqan' was again in itself a subnode of a labelless parent node, thus it did not show up, but now that this is understood, I could fix it easily (updated sources are attached). However, now we have an overlapping lens with an empty example in the Quote module:

$ augparse /usr/share/augeas/lenses/gridmapfile.aug

Syntax error in lens definition

/usr/share/augeas/lenses/gridmapfile.aug:25.2-30.44:Failed to compile mapping

/usr/share/augeas/lenses/gridmapfile.aug:23.10-.22:exception: overlapping lenses in tree union.put

    Example matched by both:

    First lens: /usr/share/augeas/lenses/dist/quote.aug:85.2-.35:

    Second lens: /usr/share/augeas/lenses/dist/quote.aug:74.2-.27:

I have altered Quote.dquote_spaces such that '#' in unquoted values are no longer accepted and the final statement looks like this:

[ lns . (bare|quoted) ]

To me that is identical to what the Quote module states:

[ lns . bare ]|[ lns . quoted ]

But augtool disagrees. Can you maybe explain the difference (in put direction) here?

Thank you once more for your time,

Xavier.

From: Raphaël Pinson [mailto:raphael.pinson at camptocamp.com] 
Sent: Monday, December 21, 2015 10:56 AM
To: Mol, Xavier (SCC)
Cc: augeas-devel at redhat.com
Subject: Re: [augeas-devel] Non-empty string from get has turned into empty node for put direction - why?

Hello Xavier,

The `mapping` lens has no label since all lenses in

    [ dn . sp . (fqan . sp)? . login . eol ]

are either subnodes (dn, fqan, login) or deletions (sp, eol)

Since Util.empty is also a label-less node, there is an ambiguity in the tree.

Most likely, you need to rethink `dn` so that it will provide the label for `mapping`.

Cheers,

Raphaël

On Mon, Dec 21, 2015 at 10:39 AM, Mol, Xavier (SCC) <xavier.mol at kit.edu> wrote:

Hello Augeas experts,

attached you can find another custom lens of mine, this time augparse identifies "overlapping lenses in tree union.put" and I don't understand why. This source file also contains some debugging output, which will produce this result:

$ augparse /usr/share/augeas/lenses/gridmapfile.aug
Concrete type of the 'mapping' regular expression:
/(([^\t\n \"#]+|\"[^\t\n \"#]+\")|\"[^\n\"]*[\t ]+[^\n\"]*\")[\t ]+((([^\t\n \"#]+|\"[^\t\n \"#]+\")|\"[^\n\"]*[\t ]+[^\n\"]*\")[\t ]+)?[.0-9A-Z_a-z-]+[\t ]*\n/
Abstract typeof the 'mapping' regular expression:
/\003\004/

Syntax error in lens definition
/usr/share/augeas/lenses/gridmapfile.aug:40.2-.42:Failed to compile lns
/usr/share/augeas/lenses/gridmapfile.aug:40.14-.39:exception: overlapping lenses in tree union.put
    Example matched by both:  {  }
    First lens: /usr/share/augeas/lenses/gridmapfile.aug:40.14-.29:
    Second lens: /usr/share/augeas/lenses/gridmapfile.aug:30.4-.44:

The node matched by the 'mapping' lens must be non-empty, which can be seen easily at the end of the regular expression, where Rx.word is included ([.0-9A-Z_a-z-]+). Yet in the put direction Augeas thinks an empty node can be used. Naturally, this is a conflict with Util.empty, which may occur in the same place as 'mapping', hence we've got an overlapping lens with 'lns'. Can anyone please explain to me why Augeas uses an empty node in the put direction for the 'mapping' lens?

Thank you for your time,
Xavier.

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