haskellPackages = with haskell.lib; haskell.packages.${compiler}.extend (pkgs.lib.composeExtensions
      (packageSourceOverrides targets)
      (self: super: {
          ghcWithPackages = p: super.ghcWithPackages (
            f: p f ++ (if false && inNixShell then [ f.cabal-install f.ghcid ] else [])
          );
          jsaddle           = self.callCabal2nix            "jsaddle"      "${jsaddle-src}/jsaddle" {};
          jsaddle-warp      = dontCheck (self.callCabal2nix "jsaddle-warp" "${jsaddle-src}/jsaddle-warp" {});
          comonad           = dontCheck super.comonad;
          extra             = dontCheck super.extra;
          SHA               = dontCheck super.SHA;
          pureMD5           = dontCheck super.pureMD5;
          unliftio          = dontCheck super.unliftio;
          semigroupoids     = dontCheck super.semigroupoids;
          megaparsec        = dontCheck super.megaparsec;
          lens              = dontCheck super.lens;
          hpack             = haskell.packages.ghc844.hpack;
          http-types        = dontCheck super.http-types;
          silently          = dontCheck super.silently;
          Diff              = appendPatch super.Diff "${writeText "Diff-Test.patch" ''
            # Diff-Test.patch
            diff --git a/test/Test.hs b/test/Test.hs
            index 4a4b3c0..f663e99 100644
            --- a/test/Test.hs
            +++ b/test/Test.hs
            @@ -134,7 +134,7 @@ prop_ppDiffR :: DiffInput -> Property
             prop_ppDiffR (DiffInput le ri) =
                 let haskDiff=ppDiff $ getGroupedDiff le ri
                     utilDiff= unsafePerformIO (runDiff (unlines le) (unlines ri))
            -    in  cover (haskDiff == utilDiff) 90 "exact match" $
            +    in  cover 90 (haskDiff == utilDiff) "exact match" $
                             classify (haskDiff == utilDiff) "exact match"
                                     (div ((length haskDiff)*100) (length utilDiff) < 110) -- less than 10% bigger
                 where
          ''}";
          Shpadoinkle-tests = haskell.packages.ghc844.callCabal2nix "tests" (gitignore ./tests) {};
      })
  );