pkgs/build-support/testers/test-equal-derivation.nix

   1 { lib, runCommand, emptyFile, nix-diff }:
   2
   3 assertion: a: b:
   4 let
   5   drvA = builtins.unsafeDiscardOutputDependency a.drvPath or (throw "testEqualDerivation second argument must be a package");
   6   drvB = builtins.unsafeDiscardOutputDependency b.drvPath or (throw "testEqualDerivation third argument must be a package");
   7   name =
   8     if a?name
   9     then "testEqualDerivation-${a.name}"
  10     else "testEqualDerivation";
  11 in
  12 if drvA == drvB then
  13   emptyFile
  14 else
  15   runCommand name
  16     {
  17       inherit assertion drvA drvB;
  18       nativeBuildInputs = [ nix-diff ];
  19     } ''
  20       echo "$assertion"
  21       echo "However, the derivations differ:"
  22       echo
  23       echo nix-diff $drvA $drvB
  24       nix-diff $drvA $drvB
  25       exit 1
  26     ''