When recently taking a look at diffoscope, I was reminded that there is
effectively no default openjdk version, you have to pick a specific
version for each package definition...

At some time in diffoscope's history, that was openjdk@12.

But there are quite a few versions to choose from:

  guix package -A openjdk | sort -V
  openjdk 9.181           out,jdk,doc     gnu/packages/java.scm:869:2
  openjdk 10.46           out,jdk,doc     gnu/packages/java.scm:1140:2
  openjdk 11.0.22         out,jdk,doc     gnu/packages/java.scm:1218:2
  openjdk 12.33           out,jdk,doc     gnu/packages/java.scm:1536:2
  openjdk 13.0.14         out,jdk,doc     gnu/packages/java.scm:1576:2
  openjdk 14.0.2          out,jdk,doc     gnu/packages/java.scm:1583:2
  openjdk 15.0.10         out,jdk,doc     gnu/packages/java.scm:1598:2
  openjdk 16.0.2          out,jdk,doc     gnu/packages/java.scm:1617:2
  openjdk 17.0.10         out,jdk,doc     gnu/packages/java.scm:1625:2
  openjdk 18.0.2.1        out,jdk,doc     gnu/packages/java.scm:1642:2
  openjdk 19.0.2          out,jdk,doc     gnu/packages/java.scm:1646:2
  openjdk 20.0.2          out,jdk,doc     gnu/packages/java.scm:1663:2
  openjdk 21.0.2          out,jdk,doc     gnu/packages/java.scm:1667:2

Some packages may only work with a specific era of openjdk, but I
suspect many of the packages in guix just picked whatever version
happened to be present when it was added to guix.

Which makes it hard to know when to update the openjdk dependency...

In the diffoscope case, it seems to have work fine with openjdk@21, with
the only result being that some openjdk-version-specific tests pass and
some are skipped as a one-for-one trade compared to the old openjdk@12.

Alternately, I would be tempted to switch to openjdk@17, which is the
current default in Debian, so has a little more testing behind it...

Though there is a bit of a perverse incentive to stick with the oldest
version that still works, due to openjdk having a very long bootstrap
chain of itself...

And then the question gets to be of diffoscope's dependencies, what
versions of openjdk do they pull in (notably enjarify, which uses
openjdk@12, although that also seems to work ok with openjdk@21)?


Would it make sense to have an openjdk "default" version, so packages
could instead depend on that, and only need to specify a version if
needed for some particular reason? Or is compatibility across openjdk
versions troublesome enough that it really always needs to be handled on
a case-by-case basis?


live well,
  vagrant