Date: Fri, 20 Nov 2015 14:40:15 -0500 From: Allan Jude <allanjude@freebsd.org> To: freebsd-hackers@freebsd.org Subject: Re: libUCL / UCL as FreeBSD config question Message-ID: <564F771F.4060408@freebsd.org> In-Reply-To: <1448048197.2765.74.camel@michaeleichorn.com> References: <5B598F72-C5DD-48FD-866D-F90E117D646E@rdsor.ro> <564F6118.5030702@freebsd.org> <1448048197.2765.74.camel@michaeleichorn.com>
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On 2015-11-20 14:36, Michael B. Eichorn wrote:
> On Fri, 2015-11-20 at 13:06 -0500, Allan Jude wrote:
>> =20
>> 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.
>>
>=20
> 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.
>=20
> I think I see two ways to avoid the POLA violation (but I am still
> rather new at this so be gentle)
>=20
> 1) Add special keys for use in memory 'value' and 'comment' such that
> the file:
>=20
> FreeBSD: {
> url: "pkg+http://pkg.FreeBSD.org/${ABI}/latest",
> mirror_type: "srv",
> signature_type: "fingerprints",
> # A comment about fingerprints
> # More comments
> fingerprints: "/usr/share/keys/pkg", # an inline comment
> enabled: yes
> }
>=20
> becomes in memory:
>=20
> FreeBSD: {
> url: "pkg+http://pkg.FreeBSD.org/${ABI}/latest",
> =20
> mirror_type: "srv",
> signature_type: "fingerprints",
> fingerprints: {
> =20
> value: "/usr/share/keys/pkg"
> comment: {
> above: "A comment
> about fingerprints\nMore comments"
> inline: "an inline comment"
> =20
> }
> }
> enabled: yes
> }
>=20
> uclcmd should just return value like:
>=20
> # uclcmd get -f /etc/pkg/FreeBSD.conf FreeBSD.fingerprints
>=20
> returns
> /usr/share/keys/pkg
>=20
> unless the comment (C?) flag is used:
> # uclcmd get -f -C /etc/pkg/FreeBSD.conf FreeBSD.fingerprints
>=20
> returns
> # A comment about fingerprints
> # More comments
> /usr/share/keys/pkg # an inline comment
>=20
> Finally if uclcmd set is used, if the session is interactive, ask the u=
ser what to do about the existing comment. If not append a note of the ch=
ange to the comment so that the file becomes:
>=20
> FreeBSD: {
> url: "pkg+http://pkg.FreeBSD.org/${ABI}/latest",
> mirror_type: "srv",
> signature_type: "fingerprints",
> # A comment about fingerprints
> # More comments
> ## Comments may be outdated, non-interactive edit 20151120T1400
> ## /usr/share/keys/pkg -> /root/keys/pkg
> fingerprints: "/root/keys/pkg", # an inline comment
> enabled: yes
> }
>=20
> 2) Assume everything can be commented, everything gets an extra pointer=
for a potential comment string. Output all comments as the 'above' style=
(bonus: comments become predictible in style). Same uclcmd behavior as d=
escribed above.
>=20
> The above are just ideas (and I know next to nothing about the guts of =
libucl), but I think comments are important, if this or something else wo=
rks I am willing to help with the implementation.
>=20
> Regards,
> Ike
>=20
This was discussed at the developer summit at BSDCan, sadly the video is
not online yet.
The issue is that UCL allows comments anywhere, for example:
#above
FreeBSD: {
/* before */ url: "pkg+http://pkg.FreeBSD.org/${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.
--=20
Allan Jude
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