Mailinglist Archive: zypp-devel (102 mails)

[Stanislav Visnovsky <visnov@xxxxxxx>]

On Streda 04 March 2009 23:04:31 Jan Kupec wrote:
> (orignal text at
> http://jniq.blogspot.com/2009/03/augeas-for-libzypp-and-zypper.html
> reposting for discussion)
>
> ------copy------
> The need for a configuration file for zypper (plus my wish for a nice
> CLI for handling it) and a visit to Raphaël Pinson's presentation at
> FOSDEM made me look at Augeas closely.
>
> Augeas enables you to read and edit your config files in a way which
> preserves comments and formatting details, allowing humans and programs
> coexist peacefully when it comes to editing configuration files. More
> than that, you can map some special structures of the file to special
> parts of the augeas tree, rather than using the generic INI file parser.
> See the zypp.conf for example (zypper.conf will have the same structure):
>
>
> [main]
> ## Option description.
> ## Default: etc.
> ##
> # disabledoption = value
>
> ## Another option description
> ##
>
> another.option = value
>
>
>
> With Augeas you can write a lens (the file contents description) which
> will map such file into a tree like this:
>
>
> /files/etc/zypp/zypp.conf/main/1
> /files/etc/zypp/zypp.conf/main/1/description[1] = "Option description."
> /files/etc/zypp/zypp.conf/main/1/description[2] = "Default: etc."
> /files/etc/zypp/zypp.conf/main/1/description[3]
> /files/etc/zypp/zypp.conf/main/1/commented
> /files/etc/zypp/zypp.conf/main/1/disabledoption = "value"
> /files/etc/zypp/zypp.conf/main/2
> /files/etc/zypp/zypp.conf/main/2/description[1] = "Another option
> description."
> /files/etc/zypp/zypp.conf/main/2/description[2]
> /files/etc/zypp/zypp.conf/main/2/another.option = "value"
>
>
>
> Note the commented node. Augeas has an API for looking for the nodes,
> getting values from them, setting the values, and finally saving the
> tree back to the config file.
>
> What does this mean for zypper? Implementing zypper conf --list is a
> piece of cake, as well as zypper conf --set another.option value.
> Commenting or uncommenting the option is a matter of adding or removing
> the commented node. Getting the option description for zypper conf
> --help some.option is easy (and maybe it is possible to map the
> multi-line ## description to a single 'description' node!).
>
> Here is a draft of lens for zypper (it will need comments and further
> improvements). To try it out you can crete a /etc/zypp/zypper.conf file
> with contents like the above example, and use the augtool like this:
>
> $ augtool -I /the/dir/with/the/zypper.aug/file
> augtool> print /files/etc/zypp/zypper.conf/
> /files/etc/zypp/zypper.conf
> /files/etc/zypp/zypper.conf/anon
> /files/etc/zypp/zypper.conf/anon/description[1] = "Configuration file
> for zypper"
> /files/etc/zypp/zypper.conf/anon/description[2]
> /files/etc/zypp/zypper.conf/anon/description[3] = "Boolean values are 0
> 1 yes no on off true false"
> /files/etc/zypp/zypper.conf/main
> /files/etc/zypp/zypper.conf/main/1
> /files/etc/zypp/zypper.conf/main/1/description[1] = "Whether to use colors"
> /files/etc/zypp/zypper.conf/main/1/description[2]
> /files/etc/zypp/zypper.conf/main/1/description[3] = "Default value:
> autodetected"
> /files/etc/zypp/zypper.conf/main/1/description[4]
> /files/etc/zypp/zypper.conf/main/1/description[5]
> /files/etc/zypp/zypper.conf/main/1/colors = "yes"
> augtool>
>
>
>
> Type help for other commands, use TAB key for completion, and check also
> the Augeas home page for more info.
>
> What does this mean for libzypp? Basically the above, with respect to
> libzypp's files. Currently, you either edit your repos.d/*.repo, locks,
> credentials, and other files by hand or you leave it to libzypp's
> frontends, or you at least take care not to write comments in those
> files, because they will all get removed upon the next change done by
> libzypp (what we do there is to rewrite the entire files from in-memory
> data upon saving). This can be easily avoided using Augeas and we can
> add an editing API for zypp.conf. Plus the bonuses described above.
>
> The library package (libaugeas0) would add 300 kiB of installed size to
> libzypp's/zypper's dependencies, (which is not little), plus an optional
> 200 kiB of the official lenses (augeas-lenses), if we decide to use them.
>
> todo: Look at Augeas' error reporting. The user can of course break the
> structure of the file in a way that the lens can't map it to the tree
> anymore. If parsing of the file will fail, we need to report why, so
> that the user can fix it.
> ------copy------
>
> I also have some code using the draft lens for zypper ready, so unless
> somebody is very much against zypper depending on libaugeas0, i will
> soon push it. BTW, can i place system-wide zypper.conf to /etc/zypp (the
> user's will be ~/.zypper.conf). Also, i plan to put the zypper.aug to
> /usr/share/zypper, so that zypper can tell augeas to read only this .aug
>  file and parse only the zypper.conf files so that it is quick.

I'm still not sure if 300kiB of a library for reading a INI file is worth it.

Stano

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