Gentoo Archives: gentoo-dev

From: Pacho Ramos <pacho@g.o>
To: gentoo-dev@l.g.o
Subject: Re: [gentoo-dev] Importance of SLOTs on Java dependencies
Date: Tue, 07 Apr 2015 18:41:22
In Reply to: [gentoo-dev] Importance of SLOTs on Java dependencies by James Le Cuirot
El dom, 05-04-2015 a las 17:16 +0100, James Le Cuirot escribió:
> Hello all, > > Firstly, I would like to take this opportunity to remind all devs > touching ebuilds with Java .jar dependencies about the importance of > restricting these dependencies to specific SLOTs. > > There is no cross-platform or even platform-specific location for > Java .jar files so each distro tends to do its own thing. Gentoo's Java > eclasses install metadata about any .jar files in a file called > package.env either at /usr/share/${PN}-${SLOT} or just /usr/share/${PN} > when the SLOT is 0. > > java-config is executed both at build time and at run time to read this > metadata so that it can build a classpath. If one of the dependencies > unexpectedly changes SLOT due to package updates then the chain breaks. > You must therefore *always* restrict the SLOT, even if that dependency > currently has a SLOT of 0. > > Why do we SLOT Java stuff so much? Java applications tend to have many > third party dependencies so it is inevitable that we would sometimes > need to have more than one version of a library installed at one time. > The write once, run anywhere nature of Java also means that upstream > doesn't expect you to run against library versions other than the ones > they shipped their application with. We do have a tool to check for > compatibility between versions though to avoid SLOT proliferation > getting out of hand. Classpath conflicts involving multiple versions > have rarely been an issue up till now but we have thought of measures > to combat this in future if needs be. > > I felt the need to write the above because I have seen many instances > where devs not familiar with Java packaging have made this mistake. Now > I need to ask what to do in the case of ebuilds that have already been > marked stable. > > To bring up a real example, I would like to bump dev-java/jna with a > new SLOT for the new version. There are several reverse dependencies, 3 > of which do not specify a SLOT, and 2 of these have already been marked > stable. Upon giving jna a new SLOT, all these packages would instantly > fail to build if jna:0 is not already installed and they would also > fail to run if jna:0 gets depcleaned. Simply leaving the stable ebuilds > as they are is therefore not an option. My preferred solution would be > create a revbump that solely amends (R)DEPEND, leaving the KEYWORDS > exactly as they are. This is controversial but what other choice is > there? I could delay the jna bump but this would push back this thread > of work by a month when I already have a huge backlog. Please do not let > bureaucracy get in the way here. > > Of course I would certainly give any maintainers a heads up before > doing this. Unfortunately, in this particular case, I contacted miknix > about dev-embedded/arduino over 2 weeks ago and haven't heard anything > back. He hasn't been seen on IRC for over 5 months. :( >
Wouldn't be possible to show a repoman warning when a dependency on any dev-java/${PN} doesn't specify a SLOT? That would save of from forgetting this in some years ;)


Subject Author
Re: [gentoo-dev] Importance of SLOTs on Java dependencies Patrice Clement <monsieurp@g.o>