core/lib/versions.nix

# Version string functions.
{ lib }:

rec {

  /*
    Break a version string into its component parts.

    Example:
      splitVersion "1.2.3"
      => ["1" "2" "3"]
  */
  splitVersion = builtins.splitVersion;

  /*
    Get the major version string from a string.

    Example:
      major "1.2.3"
      => "1"
  */
  major = v: builtins.elemAt (splitVersion v) 0;

  /*
    Get the minor version string from a string.

    Example:
      minor "1.2.3"
      => "2"
  */
  minor = v: builtins.elemAt (splitVersion v) 1;

  /*
    Get the patch version string from a string.

    Example:
      patch "1.2.3"
      => "3"
  */
  patch = v: builtins.elemAt (splitVersion v) 2;

  /*
    Get string of the first two parts (major and minor)
    of a version string.

    Example:
      majorMinor "1.2.3"
      => "1.2"
  */
  majorMinor = v: builtins.concatStringsSep "." (lib.take 2 (splitVersion v));

  /*
    Pad a version string with zeros to match the given number of components.

    Example:
      pad 3 "1.2"
      => "1.2.0"
      pad 3 "1.3-rc1"
      => "1.3.0-rc1"
      pad 3 "1.2.3.4"
      => "1.2.3"
  */
  pad =
    n: version:
    let
      numericVersion = lib.head (lib.splitString "-" version);
      versionSuffix = lib.removePrefix numericVersion version;
    in
    lib.concatStringsSep "." (lib.take n (lib.splitVersion numericVersion ++ lib.genList (_: "0") n))
    + versionSuffix;

}