The ghcWithPackage expression now has an argument 'ignoreCollisions' that
allows users to disable the path collision check like so:
(pkgs.haskellPackages.ghcWithPackages (pkgs: with pkgs; [ haskellPlatform ])).override { ignoreCollisions = true; };
See d64917ad17
for a long and detailed discussion of why these path collisions may occur.
Haskell packages -- i.e. packages built by our Cabal builder -- invariably have
the attributes 'pname' and 'version'. We use the absence of these attributes to
recognize non-Haskell packages and filter them from the closed package set
generated by closePropagation. We do this so that the generated Haskell
environment won't contain paths like "/lib/libz.a", which are part of the
closure but have nothing to do with Haskell.
The previous scheme used the attribute 'ghc' to accomplish the same thing, but
unfortunately other packages to contain a 'ghc' attribute, too, like the
old-style ghc-wrapper. Including the ghc-wrapper in this environment is
pointless, obviously. The new approach filters the ghc-wrapper successfully.
Copy only the pc files related to X11 and OpenGL.
This should allow us to build our own version of libraries like
cairo without having the native ones be accidentally dynamically
linked in to things that depend on them.
Before this patch if we `dyldinfo -dylibs libpangocairo` we can
see that it was dynamically linked against the OS X (but seemingly
built against include files from the nix one, as we would get a
runtime complaint about missing symbols)
The function ‘mkDerivation’ now checks whether the current platform
type is included in a package's meta.platform field. If not, it
throws an exception:
$ nix-build -A linux --argstr system x86_64-darwin
error: user-thrown exception: the package ‘linux-3.10.15’ is not supported on ‘x86_64-darwin’
These packages also no longer show up in ‘nix-env -qa’ output. This
means, for instance, that the number of packages shown on
x86_64-freebsd has dropped from 9268 to 4764.
Since meta.platforms was also used to prevent Hydra from building some
packages, there now is a new attribute meta.hydraPlatforms listing the
platforms on which Hydra should build the package (which defaults to
meta.platforms).
