add socket.io to interactive ghcjs environments

pkgs/development/haskell-modules/generic-builder.nix

@@ -1,5 +1,5 @@
 { stdenv, fetchurl, ghc, pkgconfig, glibcLocales, coreutils, gnugrep, gnused
-, jailbreak-cabal, hscolour, cpphs
+, jailbreak-cabal, hscolour, cpphs, nodePackages
 }:
 
 { pname
@@ -282,7 +282,8 @@ stdenv.mkDerivation ({
 
     env = stdenv.mkDerivation {
       name = "interactive-${pname}-${version}-environment";
-      nativeBuildInputs = [ ghcEnv systemBuildInputs ];
+      nativeBuildInputs = [ ghcEnv systemBuildInputs ]
+        ++ optional isGhcjs ghc."socket.io"; # for ghcjsi
       LANG = "en_US.UTF-8";
       LOCALE_ARCHIVE = optionalString stdenv.isLinux "${glibcLocales}/lib/locale/locale-archive";
       shellHook = ''