Manipulate Rails' `group(args).count` result into a hash grouped by the `args.first`. See test's `INPUT` and `EXPECTED_OUTPUT`.

group_count.rb

# https://github.com/dam13n/ruby-bury

class Hash
  def bury(*args)
    if args.count < 2
      raise ArgumentError, '2 or more arguments required'
    elsif args.count == 2
      self[args[0]] = args[1]
    else
      arg = args.shift
      self[arg] = {} unless self[arg]
      self[arg].bury(*args) unless args.empty?
    end
    self
  end
end

# Rails' group(:a, :b).count produces a hash with array keys. Sometimes, it
# would be beneficial to have a hash with the counts for :b, grouped by :a

INPUT = {
  [1, :a] => 1,
  [1, :b] => 2,
  [2, :a] => 1,
  [2, :b] => 3,
  [2, :c] => 3
}.freeze

EXPECTED_OUTPUT = {
  1 => { a: 1, b: 2 },
  2 => { a: 1, b: 3, c: 3 }
}.freeze

require 'minitest/autorun'

class Test < Minitest::Test
  def test_group_count
    output = INPUT.each_with_object({}) do |(args, count), memo|
      memo.bury(*args, count)
    end

    assert_equal EXPECTED_OUTPUT, output
  end
end