On Sat, Apr 06, 2013 at 01:08:49PM +0900, Charles Plessy wrote:
> Le Sun, Mar 31, 2013 at 07:02:15PM -0400, Scott Kitterman a écrit :
> >
> > Depends: r-base-core (>= 3.0.0~20130327) , r-base-core (<< 4)
> >
> > or you could have an API virtual package:
> >
> > r-base-api-3.0
>
> Hi Dirk and everybody,
>
> since we already have a substitution variable in most of the R packages
> (R:Depends), I think that we can use it to address the problem.
>
> First, let's define the problem: R broke backwards compatibility a couple of
> times since it has been packaged. Rebuilding packages is usually done
> swiftly,
> but there remains the problem of transitions to Testing and updates on the
> users computers. There is usually a gap of some years between breakages,
> so we do not want an over-engeneered solution.
>
> I like the idea of an api virtual package, as it requires little work from the
> parties involved and solves most of the problem. (The exception being that
> partial upgrades from Wheezy to Jessie will not be supported, but this is also
> the case in the current situation).
In short: That is not an exception but THE intention. It's the whole
point of having an api virtual package.
In long: The R package breaks compatibility in such a way that a
partial upgrade simply won't be functional. You either update them all
or none. Till now installing any package compiles against a newer R
API would pull in the newer r-base-core package to fullfill its
version requirement but would not force old R packages already
installed to also be updated. This leads to procken packages on
partial update. Introducing the api virtual package will enforce that
all R packages will be compiled against the same R API, against a
compatible r-base-core. Installing one package compiled against the
new R will force apt/aptitude to also update all the already installed
R packages, which is what is required.
> - /usr/share/R/debian/r-cran.mk, which is used in most R packages and
> produces
> the R:Depends substitution variable, would make packages depend on the
> r-api
> virtual package instead of requiring a version equal or superior to the
> version
> of r-base-core used at build time.
It might be enough to only depend on the api or you might need both,
the api virtual package and a versioned depends for a minimum version.
But that depends on the circumstances. Design it so that it is easy to
have both and so that you don't miss updating the minimum version when
required.
> - Next time R breaks backwards compatibility, Dirk would need to modify the
> Provides: line in debian/control and voilà, the new R core package can not
> be installed on a system without removing or upgrading the R library
> packages
> that were built with the old API.
It might make sense to have a single file "r-api-virtual-version" (or
so) in the source and generate the Provides: field and
/usr/share/R/debian/r-cran.mk from that single source.
> Let's discuss the details on #704805
>
> Have a nice week-end,
MfG
Goswin
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