{ lib }: {
  # Returns the Agda interface file to a given Agda file.
  #
  # The resulting path may not be normalized.
  #
  # Examples:
  # interfaceFile pkgs.agda.version "./Everything.agda" == "_build/2.6.4.3/agda/./Everything.agdai"
  # interfaceFile pkgs.agda.version "src/Everything.lagda.tex" == "_build/2.6.4.3/agda/src/Everything.agdai"
  interfaceFile = agdaVersion: agdaFile:
    "_build/" + agdaVersion + "/agda/" + lib.head
    (builtins.match "(.*\\.)l?agda(\\.(md|org|rst|tex|typ))?" agdaFile)
    + "agdai";

  # Takes an arbitrary derivation and says whether it is an agda library package
  #  that is not marked as broken.
  isUnbrokenAgdaPackage = pkg:
    pkg.isAgdaDerivation or false && !pkg.meta.broken;
}