anchor.diff:      "--disable-code-coverage"
       "--enable-compile-warnings"
       "--disable-Werror"
  -    (enFlag "introspection" (gobject-introspection != null) null)
  -    (enFlag "vala" (vala != null) null)
  +    "--${boolEn (gobject-introspection != null)}-introspection"
  +    "--${boolEn (vala != null)}-vala"
       "--disable-gtk-doc"
       "--disable-gtk-doc-html"
       "--disable-gtk-doc-pdf"
     ];
   
  -  meta = with stdenv.lib; {
  +  passthru = {
  +    srcVerification = fetchurl {
  +      inherit (src)
  +        outputHash
  +        outputHashAlgo
  +        urls;
  +      sha256Url = "https://download.gnome.org/sources/libgdata/${versionMajor}/"
  +        + "${name}.sha256sum";
  +      failEarly = true;
  +    };
  +  };
  +
  +  meta = with lib; {
       description = "GLib library for online service APIs using the GData protocol";
       homepage = https://wiki.gnome.org/Projects/libgdata;
       license = licenses.lgpl21Plus;
  
positive.code: { stdenv
  , fetchurl
  , intltool
  
  , libxml2
  , gcr
  
negative.code: }:
  
  let
    inherit (lib)
      boolEn;
  
    versionMajor = "0.17";
    versionMinor = "7";
    version = "${versionMajor}.${versionMinor}";
  in
  stdenv.mkDerivation rec {
    name = "libgdata-${version}";
  
    src = fetchurl {
      url = "mirror://gnome/sources/libgdata/${versionMajor}/${name}.tar.xz";
      hashOutput = false;
      sha256 = "8a663ef314a6d20b73c762072e0c1353fa7ec1ca3c2dee6fb85927cbda0d44fd";
    };
  
    nativeBuildInputs = [
  