haskell-modules/generic-builder.nix: use mktemp instead of TMPDIR

Using $TMPDIR here is problematic because it is not always cleared at
the end of each build, for instance when using "nix-shell --run
genericBuild". This can cause confusing errors when a nix-shell build
is trying to pull in dependencies from a previous build since it tries
to use older package conf files.

To fix, we can just use mktemp which will guarantee us a clean
directory for each build. Should have no effect in nix-build, but will
fix a common issue with using generic-builder in nix-shell.

1 files changed, 4 insertions, 3 deletions

diff --git a/pkgs/development/haskell-modules/generic-builder.nix b/pkgs/development/haskell-modules/generic-builder.nix
index bc43c39676c..e637e446e64 100644
--- a/pkgs/development/haskell-modules/generic-builder.nix
+++ b/pkgs/development/haskell-modules/generic-builder.nix
@@ -338,9 +338,10 @@ stdenv.mkDerivation ({
     echo "Build with ${ghc}."
     ${optionalString (isLibrary && hyperlinkSource) "export PATH=${hscolour}/bin:$PATH"}
 
-    setupPackageConfDir="$TMPDIR/setup-package.conf.d"
+    builddir="$(mktemp -d)"
+    setupPackageConfDir="$builddir/setup-package.conf.d"
     mkdir -p $setupPackageConfDir
-    packageConfDir="$TMPDIR/package.conf.d"
+    packageConfDir="$builddir/package.conf.d"
     mkdir -p $packageConfDir
 
     setupCompileFlags="${concatStringsSep " " setupCompileFlags}"
@@ -418,7 +419,7 @@ stdenv.mkDerivation ({
     done
 
     echo setupCompileFlags: $setupCompileFlags
-    ${nativeGhcCommand} $setupCompileFlags --make -o Setup -odir $TMPDIR -hidir $TMPDIR $i
+    ${nativeGhcCommand} $setupCompileFlags --make -o Setup -odir $builddir -hidir $builddir $i
 
     runHook postCompileBuildDriver
   '';