find_trans_licenses

#!/usr/bin/env ruby

# (C) 2017 Maarten Hoogendoorn <maarten@moretea.nl>
# Released under the GPL3.0
#
# This script finds the runtime closure of programs, and tries to find the correct license for it.
# Given that the mapping of store paths -> nix expressions does not exist, it guesses the package
# name and aborts if this guess is wrong.

require "json"
require "pp"
package_name = ARGV.first

if package_name.nil?
  puts "USAGE: #{$0} <packagename>"
  exit
end

NIX_EXPR = <<EONIX.gsub(/\s+/," ")
with (import <nixpkgs> {});
with pkgs.lib;
let
  getLicense = meta: 
    if !(meta ? license) then
      "not specified"
    else 
      if (meta.license ? fullName)
      then meta.license.fullName
      else 
        if (isList meta.license)
        then map (l: l.fullName) meta.license
        else meta.license;

  package = pkgs.${builtins.getEnv("PACKAGE")};
  showPkg = pkg: { 
    name = pkg.name;
    path = toString pkg;
    license = getLicense pkg.meta;
  };
in
{
 packagePath = toString package;
 info = showPkg package;
}
EONIX

# Guestimate of package names from derivation names;
runtime_dep_paths = `nix-store -qR $(nix-build '<nixpkgs>' -A #{package_name})`.split("\n")
deps = runtime_dep_paths.map do |dep_path| 
  name,version = dep_path.split("-",2).last.split("-",2)
  { name: name, version: version, dep_path: dep_path}
end

output = []

# Check
output = deps.map do |dep|
  nix_license_info = JSON.load `PACKAGE=#{dep[:name]} nix-instantiate --strict --json --eval --expr '#{NIX_EXPR}'`
  if nix_license_info["packagePath"] ==  dep[:dep_path]
    dep.merge({license: nix_license_info["info"]["license"] })
  else
    puts "Found wrong dependency path!"
    puts "Got path this back from nix:"
    pp nix_license_info
    puts "But actually we were interested in:"
    pp dep
    exit 1
  end
end

puts JSON.pretty_generate(output)