core/pkgs/by-name/py/python/wrap-python.nix

{ lib, python, makePythonHook, makeWrapper }:

makePythonHook {
  name = "wrap-python-hook";
  propagatedBuildInputs = [ makeWrapper ];
  substitutions.sitePackages = python.sitePackages;
  substitutions.executable = python.interpreter;
  substitutions.python = python.pythonOnBuildForHost;
  substitutions.pythonHost = python;
  substitutions.magicalSedExpression = let
    # Looks weird? Of course, it's between single quoted shell strings.
    # NOTE: Order DOES matter here, so single character quotes need to be
    #       at the last position.
    quoteVariants = [ "'\"'''\"'" ''"""'' ''"'' "'\"'\"'" ]; # hey Vim: ''

    mkStringSkipper = labelNum: quote:
      let
        label = "q${toString labelNum}";
        isSingle = lib.elem quote [ ''"'' "'\"'\"'" ];
        endQuote = if isSingle then "[^\\\\]${quote}" else quote;
      in ''
        /^[a-z]?${quote}/ {
          /${quote}${quote}|${quote}.*${endQuote}/{n;br}
          :${label}; n; /^${quote}/{n;br}; /${endQuote}/{n;br}; b${label}
        }
      '';

    # This preamble does two things:
    # * Sets argv[0] to the original application's name; otherwise it would be .foo-wrapped.
    #   Python doesn't support `exec -a`.
    # * Adds all required libraries to sys.path via `site.addsitedir`. It also handles *.pth files.
    preamble = ''
      import sys
      import site
      import functools
      sys.argv[0] = '"'$(readlink -f "$f")'"'
      functools.reduce(lambda k, p: site.addsitedir(p, k), ['"$([ -n "$program_PYTHONPATH" ] && (echo "'$program_PYTHONPATH'" | sed "s|:|','|g") || true)"'], site._init_pathinfo())
    '';

  in ''
    1 {
      :r
      /\\$|,$/{N;br}
      /__future__|^ |^ *(#.*)?$/{n;br}
      ${lib.concatImapStrings mkStringSkipper quoteVariants}
      /^[^# ]/i ${lib.replaceStrings [ "\n" ] [ ";" ] preamble}
    }
  '';
} ./wrap.sh