libUCL / UCL as FreeBSD config question

[Michael B. Eichorn]

On Fri, 2015-11-20 at 14:40 -0500, Allan Jude wrote:
> On 2015-11-20 14:36, Michael B. Eichorn wrote:
> > On Fri, 2015-11-20 at 13:06 -0500, Allan Jude wrote:
> > >  
> > > Although some limitation in libucl mean that, if you have a
> > > config
> > > that
> > > has comments in it, the comments are lost, as they are not
> > > represented
> > > in the in-memory version of the object that then gets serialized
> > > for
> > > output. If you treat the config files as a database, then this is
> > > fine,
> > > but if the user expects to still hand edit them with an editor,
> > > this
> > > is
> > > a fairly big POLA violation.
> > > 
> > 
> > Even if someday we stop editing by hand, comments are far to useful
> > IMHO to drop yet. Context is very important to what we do, and
> > sometimes keys are just to cryptic.
> > 
> > I think I see two ways to avoid the POLA violation (but I am still
> > rather new at this so be gentle)
> > 
> > 1) Add special keys for use in memory 'value' and 'comment' such
> > that
> > the file:
> > 
> > FreeBSD: {
> >   url: "pkg+http://pkg.FreeBSD.org/${ABI}/latest",
> >   mirror_type: "srv",
> >   signature_type: "fingerprints",
> >   # A comment about fingerprints
> >   # More comments
> >   fingerprints: "/usr/share/keys/pkg", # an inline comment
> >   enabled: yes
> > }
> > 
> > becomes in memory:
> > 
> > FreeBSD: {
> >   url: "pkg+http://pkg.FreeBSD.org/${ABI}/latest",
> >  
> > mirror_type: "srv",
> >   signature_type: "fingerprints",
> >   fingerprints: {
> >  
> >   value: "/usr/share/keys/pkg"
> >     comment: {
> >       above: "A comment
> > about fingerprints\nMore comments"
> >       inline: "an inline comment"
> >    
> > }
> >   }
> >   enabled: yes
> > }
> > 
> > uclcmd should just return value like:
> > 
> > # uclcmd get -f /etc/pkg/FreeBSD.conf FreeBSD.fingerprints
> > 
> > returns
> > /usr/share/keys/pkg
> > 
> > unless the comment (C?) flag is used:
> > # uclcmd get -f -C /etc/pkg/FreeBSD.conf FreeBSD.fingerprints
> > 
> > returns
> > # A comment about fingerprints
> > # More comments
> > /usr/share/keys/pkg	# an inline comment
> > 
> > Finally if uclcmd set is used, if the session is interactive, ask
> > the user what to do about the existing comment. If not append a
> > note of the change to the comment so that the file becomes:
> > 
> > FreeBSD: {
> >   url: "pkg+http://pkg.FreeBSD.org/${ABI}/latest",
> >   mirror_type: "srv",
> >   signature_type: "fingerprints",
> >   # A comment about fingerprints
> >   # More comments
> >   ## Comments may be outdated, non-interactive edit 20151120T1400
> >   ## /usr/share/keys/pkg -> /root/keys/pkg
> >   fingerprints: "/root/keys/pkg", # an inline comment
> >   enabled: yes
> > }
> > 
> > 2) Assume everything can be commented, everything gets an extra
> > pointer for a potential comment string. Output all comments as the
> > 'above' style (bonus: comments become predictible in style). Same
> > uclcmd behavior as described above.
> > 
> > The above are just ideas (and I know next to nothing about the guts
> > of libucl), but I think comments are important, if this or
> > something else works I am willing to help with the implementation.
> > 
> > Regards,
> > Ike
> > 
> 
> This was discussed at the developer summit at BSDCan, sadly the video
> is
> not online yet.
> 
> The issue is that UCL allows comments anywhere, for example:
> 
> #above
> FreeBSD: {
>    /* before */ url: "pkg+http://pkg.FreeBSD.org/${ABI}/latest",
>    mirror_type: /* middle */ "srv",
>    signature_type: "fingerprints", /* after */
>    # under
>    fingerprints: "/root/keys/pkg", # inline-after
>    enabled: yes
> }
> 
> Etc. So the solution that was discussed was changing libucl to use an
> Abstract Syntax Tree, but that is a lot of work. So for now, I am not
> sure what the best approach is.
> 
> 
> 

Ok, I am satified that comments are a topic of discussion and that
improvement may be forthcoming.

I will wait on the video before making more chatter.

Ike
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