pkgs/development/compilers/ghc/with-packages.nix: improve recognition of Haskell packages

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.

1 files changed, 2 insertions, 1 deletions

diff --git a/pkgs/development/compilers/ghc/with-packages.nix b/pkgs/development/compilers/ghc/with-packages.nix
index b32b12d5b954..8f5e8616a84e 100644
--- a/pkgs/development/compilers/ghc/with-packages.nix
+++ b/pkgs/development/compilers/ghc/with-packages.nix
@@ -7,10 +7,11 @@ let
   packageDBFlag = if ghc761OrLater then "--package-db" else "--package-conf";
   libDir        = "$out/lib/ghc-${ghc.version}";
   packageCfgDir = "${libDir}/package.conf.d";
+  isHaskellPkg  = x: (x ? pname) && (x ? version);
 in
 buildEnv {
   name = "haskell-env-${ghc.name}";
-  paths = stdenv.lib.filter (x: x ? ghc) (stdenv.lib.closePropagation packages) ++ [ghc];
+  paths = stdenv.lib.filter isHaskellPkg (stdenv.lib.closePropagation packages) ++ [ghc];
   postBuild = ''
     . ${makeWrapper}/nix-support/setup-hook