Use Nix to build vim with +python support + custom python libraries

config.nix

# I wanted to use ensime with vim, which requires vim + python + some python packages (websocket_client + sexpdata)
# unfortunately, nix would build vim with a python that didn't have access to my system libraries (for referential transperancy)
# so I needed to provide to `vim_configurable.nix` the right python to use *and* enable python, lua, etc. support.
# I also wanted to keep my `.vimrc` separate because some of the vim packages I use weren't available.
#
# install via: `nix-env -f '<nixpkgs>' -iA myCoolVim` or `nix-env -I nixpkgs=/path/to/your/nixpkgs -f '<nixpkgs>' -iA myCoolVim`
#
# out put of `vim --version` below.

{
  packageOverrides = super: let self = super.pkgs; in
  {

    myPy = self.python.buildEnv.override {
      extraLibs = [ self.pythonPackages.websocket_client  self.pythonPackages.sexpdata ];
      ignoreCollisions = true;
    };

    myCoolVim = self.lib.overrideDerivation (self.vim_configurable.override { python = self.myPy; }) (o: {
      aclSupport              = false;
      cscopeSupport           = true;
      darwinSupport           = false;
      fontsetSupport          = true;
      ftNixSupport            = true;
      gpmSupport              = true;
      gui                     = false;
      hangulinputSupport      = false;
      luaSupport              = true;
      multibyteSupport        = true;
      mzschemeSupport         = true;
      netbeansSupport         = false;
      nlsSupport              = false;
      perlSupport             = false;
      pythonSupport           = true;
      rubySupport             = true;
      sniffSupport            = false;
      tclSupport              = false;
      ximSupport              = false;
      xsmpSupport             = false;
      xsmp_interactSupport    = false;
    });
  };
}


# ☭ vim --version
# VIM - Vi IMproved 7.4 (2013 Aug 10, compiled Jan  1 1970 00:00:01)
# Included patches: 1-826
# Compiled by aaronlevin
# Huge version with GTK2 GUI.  Features included (+) or not (-):
# +acl             +farsi           +mouse_netterm   +syntax
# +arabic          +file_in_path    +mouse_sgr       +tag_binary
# +autocmd         +find_in_path    -mouse_sysmouse  +tag_old_static
# +balloon_eval    +float           +mouse_urxvt     -tag_any_white
# +browse          +folding         +mouse_xterm     -tcl
# ++builtin_terms  -footer          +multi_byte      +terminfo
# +byte_offset     +fork()          +multi_lang      +termresponse
# +cindent         -gettext         -mzscheme        +textobjects
# +clientserver    -hangul_input    +netbeans_intg   +title
# +clipboard       +iconv           +path_extra      +toolbar
# +cmdline_compl   +insert_expand   -perl            +user_commands
# +cmdline_hist    +jumplist        +persistent_undo +vertsplit
# +cmdline_info    +keymap          +postscript      +virtualedit
# +comments        +langmap         +printer         +visual
# +conceal         +libcall         +profile         +visualextra
# +cryptv          +linebreak       +python          +viminfo
# +cscope          +lispindent      -python3         +vreplace
# +cursorbind      +listcmds        +quickfix        +wildignore
# +cursorshape     +localmap        +reltime         +wildmenu
# +dialog_con_gui  +lua             +rightleft       +windows
# +diff            +menu            +ruby            +writebackup
# +digraphs        +mksession       +scrollbind      +X11
# +dnd             +modify_fname    +signs           -xfontset
# -ebcdic          +mouse           +smartindent     -xim
# +emacs_tags      +mouseshape      -sniff           -xsmp
# +eval            +mouse_dec       +startuptime     +xterm_clipboard
# +ex_extra        -mouse_gpm       +statusline      -xterm_save
# +extra_search    -mouse_jsbterm   -sun_workshop    +xpm
#    system vimrc file: "$VIM/vimrc"
#      user vimrc file: "$HOME/.vimrc"
#  2nd user vimrc file: "~/.vim/vimrc"
#       user exrc file: "$HOME/.exrc"
#   system gvimrc file: "$VIM/gvimrc"
#     user gvimrc file: "$HOME/.gvimrc"
# 2nd user gvimrc file: "~/.vim/gvimrc"
#     system menu file: "$VIMRUNTIME/menu.vim"
#   fall-back for $VIM: "
# /nix/store/699nhhzfwcppbygc2sxg8f4mkn0s2aqr-vim_configurable-7.4.826/share/vim
# "
# Compilation: gcc -c -I. -Iproto -DHAVE_CONFIG_H -DFEAT_GUI_GTK  -I/nix/store/857sfqpl6fyixih2vcw89lwpyahx14d1-gtk+-2.24.29-dev/include/gtk-2.0 -I/nix/store/xsmzpx4qcyhrx506gm7hz0qxlixixb1j-gtk+-2.24.29/lib/gtk-2.0/include -I/nix/store/v84fvqd556j9q64d0n9hc4zn23y8ccqd-glib-2.46.2-dev/include/glib-2.0 -I/nix/store/4yqw3m09xrhv8ykfdxzjds41d3c7klfj-glib-2.46.2/lib/glib-2.0/include -I/nix/store/ddljnw1f7lqn0jpy8rapmi4n1n579rx1-cairo-1.14.6-dev/include/cairo -I/nix/store/36m0i7w0k2fi03ji5wpi0i4xbpk3mkhc-freetype-2.6.2-dev/include/freetype2 -I/nix/store/36m0i7w0k2fi03ji5wpi0i4xbpk3mkhc-freetype-2.6.2-dev/include -I/nix/store/0v3d3hsdnazn6lscpmffcyn67qqwhk3x-fontconfig-2.11.1-dev/include -I/nix/store/vjqh3yg73wg6xjjicnw33d6lbkkm1l69-expat-2.1.0-dev/include -I/nix/store/36m0i7w0k2fi03ji5wpi0i4xbpk3mkhc-freetype-2.6.2-dev/include/freetype2 -I/nix/store/l4nxxf2qkbplk7nnbiiabafj5l0ksswg-pango-1.38.1-dev/include/pango-1.0 -I/nix/store/n80dqxzddqlxrba8n4nkbwbjyrrnsa7j-gdk-pixbuf-2.32.3-dev/include/gdk-pixbuf-2.0 -I/nix/store/kbfdb7pli3gjlxdk8dsn68xcqll6x5d1-atk-2.18.0-dev/include/atk-1.0 -I/usr/local/include  -g -O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1       
# Linking: gcc -L/nix/store/xsmzpx4qcyhrx506gm7hz0qxlixixb1j-gtk+-2.24.29/lib -L/nix/store/4yqw3m09xrhv8ykfdxzjds41d3c7klfj-glib-2.46.2/lib -L/nix/store/292jvr8myz52gydi5z6san2dyndingg2-cairo-1.14.6/lib -L/nix/store/i801jlsjxfg48kq0dlvh9fb30jpaiwpd-fontconfig-2.11.1-lib/lib -L/nix/store/97bpv541iyydvp0qc1vnvdka3grzwspb-freetype-2.6.2/lib -L/nix/store/hlpsvdpdk5sb2y6g0hlhdrvp9fl3ffxf-pango-1.38.1/lib -L/nix/store/0mz4p7pm5acvldp79ch6m1bkqbniz6r0-gdk-pixbuf-2.32.3/lib -L/nix/store/rq3r1hhsk6214bvcjmvi68187iqxp1fc-atk-2.18.0/lib  -L. -fstack-protector -rdynamic -Wl,-export-dynamic  -L/usr/local/lib -Wl,--as-needed -o vim   -L/nix/store/xsmzpx4qcyhrx506gm7hz0qxlixixb1j-gtk+-2.24.29/lib -L/nix/store/4yqw3m09xrhv8ykfdxzjds41d3c7klfj-glib-2.46.2/lib -L/nix/store/292jvr8myz52gydi5z6san2dyndingg2-cairo-1.14.6/lib -L/nix/store/i801jlsjxfg48kq0dlvh9fb30jpaiwpd-fontconfig-2.11.1-lib/lib -L/nix/store/97bpv541iyydvp0qc1vnvdka3grzwspb-freetype-2.6.2/lib -L/nix/store/hlpsvdpdk5sb2y6g0hlhdrvp9fl3ffxf-pango-1.38.1/lib -L/nix/store/0mz4p7pm5acvldp79ch6m1bkqbniz6r0-gdk-pixbuf-2.32.3/lib -L/nix/store/rq3r1hhsk6214bvcjmvi68187iqxp1fc-atk-2.18.0/lib -lgtk-x11-2.0 -lgdk-x11-2.0 -lpangocairo-1.0 -latk-1.0 -lcairo -lgdk_pixbuf-2.0 -lgio-2.0 -lpangoft2-1.0 -lpango-1.0 -lgobject-2.0 -lglib-2.0 -lfontconfig -lfreetype -lSM -lICE -lXpm -lXt -lX11 -lSM -lICE  -lm -lncurses -lnsl   -ldl  -L/nix/store/s9lw3njm82hijgf8xbrvkqvz2y80aash-lua-5.1.5/lib -llua  -L/nix/store/b4k601iaixg66fkxxxi09rlx2j4p1s66-python-2.7.11/lib/python2.7/config -lpython2.7 -lpthread -ldl -lutil -lm -Xlinker -export-dynamic   -Wl,-R/nix/store/hl825hpk28qbzx61nbn9ab8sd8y8j18y-ruby-2.3.0-p0/lib -L/nix/store/hl825hpk28qbzx61nbn9ab8sd8y8j18y-ruby-2.3.0-p0/lib -lruby -lpthread -ldl -lcrypt -lm  -L/nix/store/hl825hpk28qbzx61nbn9ab8sd8y8j18y-ruby-2.3.0-p0/lib