anchor.diff:        --set JAVA_HOME "${openjdk}"
     '';
   
  +  passthru = {
  +    srcVerification = fetchurl {
  +      inherit (src)
  +        outputHash
  +        outputHashAlgo
  +        urls;
  +      sha1Url = map (n: "${n}.sha1") src.urls;
  +      failEarly = true;
  +    };
  +  };
  +
     meta = with lib; {
       description = "Distributed RESTful search engine built on top of Lucene";
       homepage = https://www.elastic.co/products/elasticsearch;
  
positive.code: 
    sources = {
      "5.5" = {
        version = "5.5.2";
        sha1Confirm = "91b3b3c823fafce54609ed5c9075d9cf50b2edff";
        sha256 = "0870e2c0c72e6eda976effa07aa1cdd06a9500302320b5c22ed292ce21665bf1";
      };
      "6.0" = {
        version = "6.0.0-beta2";
        sha1Confirm = "c3f7c1685fc4925a4fac96fa4dfb1706c85acde6";
        sha256 = "0c200154c4980ad6e278d9c9ee9e2ca22d2c501c4c67e6fe748adde31aa36b0e";
      };
    };
  
negative.code: 
    src = fetchurl {
      url = "https://artifacts.elastic.co/downloads/elasticsearch/${name}.tar.gz";
      hashOutput = false;
      inherit (source) sha256;
    };
  
    nativeBuildInputs = [
  