merging and shortening default.nix and shell.nix

Author: CohenCyril

default.nix

@@ -1,44 +1,31 @@
 {withEmacs ? false,
  nixpkgs ?  (fetchTarball {
-  url = "https://github.com/CohenCyril/nixpkgs/archive/7f59c094a0e5c8659856e611075fe88d6177830f.tar.gz";
-  sha256 = "00cf4r8dqfx2hwlwaqb239h72m4s0wl97i98424xd4hki0vzifbi";
+  url = "https://github.com/CohenCyril/nixpkgs/archive/8d04d29adb547353ed9fb5c5c4aa6d540e198366.tar.gz";
+  sha256 = "1v4l37xkadpnkydpycnk9hrjgh6yc792k66yi7f6203zzr0phzx8";
 }),
  coq-version ? "8.11",
  print-env ? false
 }:
-with import nixpkgs {};
-let
-  pgEmacs = emacsWithPackages (epkgs:
-    with epkgs.melpaStablePackages; [proof-general]);
-  myCoqPackages = {
-    "8.10" = coqPackages_8_10;
-    "8.11" = coqPackages_8_11;
-    }."${coq-version}";
-  coq = myCoqPackages.coq;
-  coq-elpi = myCoqPackages.coq-elpi.overrideAttrs(o: {
-    name = "coq8.11-elpi-v1.4.0";
-    src = fetchTarball https://github.com/LPCIC/coq-elpi/archive/v1.4.0.tar.gz;
-  });
-in
-stdenv.mkDerivation {
+with import nixpkgs {
+  overlays = [ (super: self: {
+    coqPackages = { "8.11" = super.coqPackages_8_11;  }."${coq-version}";
+    coq = self.coqPackages.coq;
+  })];
+};
+let pgEmacs = emacsWithPackages (epkgs: with epkgs.melpaStablePackages; [proof-general]); in
+coqPackages.hierarchy-builder.overrideAttrs (old: {
   name = "coq${coq.coq-version}-hierarchy-builder-dev";
-
   src = ./.;
-
-  nativeBuildInputs = [ which ];
-  buildInputs = [ coq coq.ocaml coq.ocamlPackages.elpi coq-elpi ];
-
-  installPhase = ''make -f Makefile.coq VFILES=structures.v COQLIB=$out/lib/coq/${coq.coq-version}/ install'';
-
-  meta = {
-    description = "Coq plugin embedding ELPI.";
-    maintainers = [ stdenv.lib.maintainers.cohencyril ];
-    license = stdenv.lib.licenses.lgpl21;
-    inherit (coq.meta) platforms;
-    inherit (src.meta) homepage;
-  };
-
-  passthru = {
-    compatibleCoqVersions = stdenv.lib.flip builtins.hasAttr params;
-  };
+  buildInputs = old.buildInputs ++
+                (if lib.trivial.inNixShell then lib.optional withEmacs pgEmacs
+                 else []);
 }
+// (if lib.trivial.inNixShell then {
+  shellHook = ''
+    nixEnv (){
+      echo "Here is your work environement:"
+      for x in $buildInputs; do printf "  "; echo $x | cut -d "-" -f "2-"; done
+      echo "you can pass option '--argstr coq-version \"x.y\"' to nix-shell to change coq versions"
+    }
+  '' + lib.optionalString print-env "nixEnv";
+} else {}))