Needs rebase

@joachifm Rebased.

Shouldn't this use -DCMAKE_INSTALL_PREFIX=$out instead of $out/usr? If you do, then (to answer @teh's question) I believe this package will work when listed in the system-wide configuration.nix in the services.dbus.packages setting. It isn't immediately obvious to me that there's any way to use it with nix-env, at least from what I can find of the current DBus packaging in nixpkgs.

In fact, if you add cmake to buildInputs, then that prefix is the default and the whole preConfigure block can be replaced with:

 cmakeFlags = "-DBUILD_EXTENSION=OFF";
 postConfigure = ''
 substituteInPlace cmake_install.cmake --replace "/etc" "$out/etc"
 '';

After doing that, I also had to remove the two rm calls from postInstall. I can't figure out why they started failing, but I also don't see what good they were doing.

I don't think the version of this package that's currently on master works as-is, but I think the above fixes should get it close.

I found more bugs in the version of this patch that's on master: the wrapper script is not constructed correctly. I would very much like this reviewed by someone more experienced with Nix packaging than I am.

• The wrapProgram call is missing the separator (:) arguments for the --prefix PATH flags.
• The specified PATH prefixes don't point to directories containing programs; ${dbus}/bin/dbus should just be ${dbus}/bin and ${gnome3.gnome_shell} should be ${gnome3.gnome_shell}/bin. Although I'm not convinced that either directory actually needs to be on the PATH.
• The program gets wrapped twice due to the use of wrapGAppsHook, which leads to infinite recursion and eventually the bash "argument list too long" error.

I still haven't gotten this to work even with all that fixed since I wanted to test it using nix-env instead of installing system-wide. My DBus session bus apparently isn't looking in ~/.nix-profile/share like the documentation says it should if the value of XDG_DATA_DIRS were available to it, so I think my gdm3 X session isn't starting it with the full environment for my profile. I guess that's a separate issue.

Here's the standalone expression I'm currently testing with. I suspect more things can be deleted from it, but since I can't fully test it I've left the buildInputs and PATH alone. However I did switch to a released version rather than a random git commit.

with import <nixpkgs> { };
  
stdenv.mkDerivation rec {
  name = "chrome-gnome-shell";
  version = "9";
  src = fetchurl {
    url = "https://git.gnome.org/browse/chrome-gnome-shell/snapshot/${name}-${version}.tar.xz";
    sha256 = "0j6lzlp3jvkpnkk8s99y3m14xiq94rjwjzy2pbfqgv084ahzmz8i";
  };

  buildInputs = [ cmake gnome3.gnome_shell makeWrapper jq dbus gobjectIntrospection
    python python27Packages.requests python27Packages.pygobject3 wrapGAppsHook];
  
  cmakeFlags = "-DBUILD_EXTENSION=OFF";
  postConfigure = ''
    substituteInPlace cmake_install.cmake --replace "/etc" "$out/etc"
  '';

  dontWrapGApps = true;
  postFixup = ''
    wrapProgram $out/bin/chrome-gnome-shell \
      --prefix PATH : '${dbus}/bin:${gnome3.gnome_shell}/bin' \
      --prefix PYTHONPATH : "$PYTHONPATH" \
      "''${gappsWrapperArgs[@]}"
  '';
}

Any idea how to get this to work, even for system wide packages? Snippet from my config:

environment.systemPackages = [ 
    pkgs.firefox-devedition-bin
];
services.dbus.packages = [ pkgs.chrome-gnome-shell ];

@pierrebeaucamp, i didn't understand your question, but maybe this Unix.SE answer can help.