The new version of hackage2nix adds an automatic jailbreak=true attribute to
all builds that are known to fail because of unsatisfied dependency version
constraints. Of course, hackage2nix is only able to detect these problems for
the default package set -- "haskellngPackages" -- that's built with GHC 7.8.4.
It cannot know problems that might arise if you build a package with a
different version of GHC, which comes with different versions of the core
libraries. This change "fixed" 806 builds: http://hydra.cryp.to/eval/85620.
Please pay attention to possible jailbreaks when reporting build errors
upstream! If a build was run with jailbreaking enabled, the build log says
| Running jailbreak-cabal to lift version restrictions on build inputs.
at the very top. Upstream bug reports about build errors should contain that
information, i.e. the package author should know that you're building with
different (newer!) library versions than they're specifying.
Furthermore, build expressions no longer contain an explicit list of every
Cabal flag setting. Instead, we trust that Cabal figures out an appropriate
configuration at build time. This makes the build expressions more space to
adapt to different configuration at the cost of being slightly less
deterministic.
0e6fd630a4