[augeas-devel] Inconsistent matching of multiple predicates (involving last/position)

[Mol, Xavier (SCC)]

> so virtually nothing should have changed, besides the timestamps on automaster.aug.
I lied, something else did indead change: the last line of /etc/auto.master! If it is not empty or a sole '#' character, I can use last() as secondary predicate successfully. Though position() will still fail either way.

Best regards,
Xavier.

> -----Original Message-----
> From: augeas-devel-bounces at redhat.com [mailto:augeas-devel-bounces at redhat.com] On Behalf Of Mol, Xavier (SCC)
> Sent: Friday, August 28, 2015 2:24 PM
> To: Dominic Cleal
> Cc: augeas-devel at redhat.com
> Subject: Re: [augeas-devel] Inconsistent matching of multiple predicates (involving last/position)
> 
> Hi again,
> 
> for some reason I cannot explain, now a couple of things work suddenly as expected:
> 
> augtool> match $master/*[last()]
> /files/etc/auto.master/3 = +
> augtool> match $master/*[position() = 2]
> /files/etc/auto.master/#comment[1] = Sample auto.master file
> augtool> match $master/*[label() != '#comment'][last()]
> /files/etc/auto.master/3 = +
> 
> 
> Though not everything does...
> 
> augtool> match $master/*[label() != '#comment']
> /files/etc/auto.master/1 = /misc
> /files/etc/auto.master/2 = /net
> /files/etc/auto.master/3 = +
> augtool> match $master/*[label() != '#comment'][position() = 2]
>   (no matches)
> 
> 
> Yes, I did edit a copy of automaster.aug, just to experiment with a labeled mount point, but I moved back the original, so virtually nothing
> should have changed, besides the timestamps on automaster.aug. Is there maybe some kind of cacheing in Augeas, which could have
> updated just now (instead of when I installed the new packages)?
> 
> Best regards,
> Xavier.
> 
> > -----Original Message-----
> > From: augeas-devel-bounces at redhat.com [mailto:augeas-devel-bounces at redhat.com] On Behalf Of Mol, Xavier (SCC)
> > Sent: Friday, August 28, 2015 1:58 PM
> > To: Dominic Cleal
> > Cc: augeas-devel at redhat.com
> > Subject: Re: [augeas-devel] Inconsistent matching of multiple predicates (involving last/position)
> >
> > Hi Dominic,
> >
> > I've updated Augeas, but for me the results stay the same...
> >
> > augtool> match /augeas/version
> > /augeas/version = 1.4.0
> > augtool> match $master/*[label() != '#comment'][map]
> > /files/etc/auto.master/1 = /misc
> > /files/etc/auto.master/2 = /net
> > /files/etc/auto.master/3 = +
> > augtool> match $master/*[label() != '#comment'][position() = 2]
> >   (no matches)
> > augtool> match $master/*[label() != '#comment'][last()]
> >   (no matches)
> >
> >
> > Maybe I misunderstand how to use last()/position() in the first place, because even this fails:
> >
> > augtool> match $master/*[last()]
> >   (no matches)
> > augtool> match $master/*[position() = 1]
> >   (no matches)
> >
> >
> > This should return the very last and first node, regardless whether it’s a comment or a mapping, right? Though it may work, if I mess
> > around with the lens and introduce a label for the mount points.
> >
> > augtool> print $master/*[label() != '#comment']
> > /files/etc/auto.master/mount[1] = "/misc"
> > /files/etc/auto.master/mount[1]/map = "/etc/auto.misc"
> > /files/etc/auto.master/mount[2] = "/net"
> > /files/etc/auto.master/mount[2]/map = "-hosts"
> > /files/etc/auto.master/mount[3] = "+"
> > /files/etc/auto.master/mount[3]/map = "auto.master"
> > augtool> match $master/mount[last()]
> > /files/etc/auto.master/mount[3] = +
> > augtool> match $master/mount[position() = 2]
> > /files/etc/auto.master/mount[2] = /net
> >
> >
> > > > I'd guess position() is the position under the original node, not in the
> > > > filtered results (!= '#comment').
> > Then this would qualify as a bug, correct? Quote from the Augeas wiki "Multiple predicates are evaluated by filtering node sets
> > successively".
> >
> > match $master/*[label() != '#comment'][position() = 2]
> >
> > _in general_ should not yield the same result as
> >
> > match $master/*[position() = 2][label() != '#comment']
> >
> > which is what you assume position() does (the result will be the same only if the filter for comments has no effect, e.g. when both first
> > nodes are no comment)?
> >
> >
> > Best regards,
> > Xavier.
> >
> > > -----Original Message-----
> > > From: augeas-devel-bounces at redhat.com [mailto:augeas-devel-bounces at redhat.com] On Behalf Of Mol, Xavier (SCC)
> > > Sent: Friday, August 28, 2015 11:02 AM
> > > To: Dominic Cleal
> > > Cc: augeas-devel at redhat.com
> > > Subject: Re: [augeas-devel] Inconsistent matching of multiple predicates (involving last/position)
> > >
> > > Thank you for your quick reply, Dominic!
> > >
> > > I'll see if I can update Augeas first.
> > >
> > > Best regards,
> > > Xavier.
> > >
> > > > -----Original Message-----
> > > > From: Dominic Cleal [mailto:dcleal at redhat.com]
> > > > Sent: Friday, August 28, 2015 10:58 AM
> > > > To: Mol, Xavier (SCC)
> > > > Cc: augeas-devel at redhat.com
> > > > Subject: Re: Inconsistent matching of multiple predicates (involving last/position)
> > > >
> > > > On 28/08/15 09:50, Mol, Xavier (SCC) wrote:
> > > > > What Augeas version?
> > > > > 	augeas-1.0.0-10.el6.x86_64
> > > >
> > > > This is quite old, it appears to have been fixed some time since.
> > > >
> > > > > augtool> defvar master /files/etc/auto.master
> > > > > augtool> match $master/*[map]
> > > > > /files/etc/auto.master/1 = /misc
> > > > > /files/etc/auto.master/2 = /net
> > > > > /files/etc/auto.master/3 = +
> > > > > augtool> match $master/*[label() != '#comment']
> > > > > /files/etc/auto.master/1 = /misc
> > > > > /files/etc/auto.master/2 = /net
> > > > > /files/etc/auto.master/3 = +
> > > > >
> > > > > **)
> > > > > augtool> match $master/*[map][last()]
> > > > > /files/etc/auto.master/3 = +
> > > > > augtool> match $master/*[map][position() = 2]
> > > > > /files/etc/auto.master/2 = /net
> > > > > augtool> match $master/*[label() != '#comment'][last()]
> > > > >   (no matches)
> > > >
> > > > On 1.4.0:
> > > >
> > > > augtool> match $master/*[label() != '#comment'][last()]
> > > > /files/etc/auto.master/3 = +
> > > >
> > > > > augtool> match $master/*[label() != '#comment'][position() = 2]
> > > > >   (no matches)
> > > >
> > > > augtool> match $master/*[label() != '#comment'][position() = 3]
> > > > /files/etc/auto.master/1 = /misc
> > > > augtool> match $master/*[label() != '#comment'][position() = 6]
> > > > /files/etc/auto.master/2 = /net
> > > >
> > > >
> > > > A git bisect would probably narrow down which commit fixed it, as I
> > > > can't remember now.  If you need it fixed in el6, please file a BZ with
> > > > Red Hat.
> > > >
> > > > --
> > > > Dominic Cleal
> > > > Red Hat Engineering
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