Bug#619574: python-apt: Provide access for task associated with a package

[Patrick Schoenfeld <schoenfeld@debian.org>]

Hi Julian,

On Fri, Mar 25, 2011 at 11:21:02AM +0100, Julian Andres Klode wrote:
> On Fri, Mar 25, 2011 at 10:57:03AM +0100, Patrick Schoenfeld wrote:
> > Package: python-apt
> > Severity: wishlist
> > 
> > Hi,
> > 
> > currently the python-apt bindings for the apt package cache do not
> > provide access to the task associated with a package. I have a use-case
> > where I need it.
> > 
> > The information can be gathered from the Packages file,
> > where for each Package, which is a member of a task, a key-value pair
> > "Task: foo" is stored.
> > 
> > It would be nice if python-apt provided a method task
> > in apt.packagePackage() objects. Apart from this it would be nice to
> > have functions in the cache object to access list of tasks and
> > associated packages..
> 
> Use Version.record["Task"].split():

thanks for showing me a way to get that information,
as I would have never found that myself.


>     >>> import apt
>     >>> apt.Cache()["gnome"].candidate.record["Task"].split()
>     ['gnome-desktop']
> 
> The tasks are not in the cache, and this is easy enough, so
> I don't think we need an extra method for it.

Well, easy enough is an interesting term in that case. Maybe
documentation could be improved, because its very hard to get to that
information if you did not write the API yourself.
>From documentation and my apt understanding I could get as far to
understand that each package has a (installation) candidate
with all package-version-specific informations associated to it.

API doc says:
"Return the candidate version of the package"

It takes something to understand that formulation like you eventually
meant it.
I suggest the following wording to make it more accurate and better
understandable:

"Return the candidate of the package as a Version() object, which stores
all information about the candidate version."

This probably gives a hint, that it does not only return "1.0.0-1" in an
object representation but all data associated to the given candidate.

Now to the Version() class:
The docstring reads as:
"Representation of a package version"

Yes, if you already know the API or if you are good at guessing, its
clear what this one sentence means. A short introduction whats possible
with the module would be nice though.

Maybe something like:

"""
Representation of a package version

This class representates a package version and provides access to all
version-specific package attributes.
"""

Now, if one is so far to get to the point of having a Version() object,
where to go from there?
This object does have all kind of property accessors, but none for the
task field of the candidate version of the package.

Just as a sidenote: This would be a good point to have a "def task()"
which would return the task associated to that candidate version.
I know you think using records()["Task"] is "easy enough", but OTOH it
would be "easy enough" to access the Priority of the given candver by
this means as well. Nevertheless you provide a priority function for it.

Now there is records(), which is nice, but again, by its documentation
its not reall obvious that it can lead to the answer you gave:

"Return a Record() object for this version"

Suggestion:
"Return a Record() object for this version, which provides access
to the raw attributes of the candidate version"

Last but not least the Record() class:
"""
Represent a pkgRecord

It can be access liked a dict..

"""

This could be easily improved by writing:

"Represent a package record as stored in the Packages file"


Best Regards,
Patrick