hash-string-to-ruby-hash.rb

 # Just a copy of https://stackoverflow.com/a/30724359/1825727
  def from_hashstring(value)
    json_string = value
                  .gsub(/([{,]\s*):([^>\s]+)\s*=>/, '\1"\2"=>') # Handle ruby symbols as keys
                  .gsub(/([{,]\s*)([0-9]+\.?[0-9]*)\s*=>/, '\1"\2"=>') # Handle numbers as keys
                  .gsub(/([{,]\s*)(".+?"|[0-9]+\.?[0-9]*)\s*=>\s*:([^,}\s]+\s*)/, '\1\2=>"\3"') # Handle symbols as values
                  .gsub(/([\[,]\s*):([^,\]\s]+)/, '\1"\2"') # Handle symbols in arrays
                  .gsub(/([{,]\s*)(".+?"|[0-9]+\.?[0-9]*)\s*=>/, '\1\2:') # Finally, convert => to :

    JSON.parse(json_string)
  rescue
    value
  end
    
  # Test cases for more explanation

  test 'from_hashstring works on basic ruby hash' do
    string = '{"url"=>"TEST.png", "type"=>"image/png", "height"=>512}'

    hash = from_hashstring string
    assert_equal Hash, hash.class
    assert_equal 'image/png', hash['type']
    assert_equal 512, hash['height']

    assert_equal 'abc', from_hashstring('abc')
  end

  test 'from_hashstring works on symbols' do
    string = '{:url => 123}'
    assert_equal 123, from_hashstring(string)['url']
  end

  test 'from_hashstring works on numeric keys' do
    string = '{0 => 123}'
    assert_equal 123, from_hashstring(string)['0']
  end

  test 'from_hashstring works on symbol values' do
    string = '{"abc" => :test}'
    assert_equal 'test', from_hashstring(string)['abc']
  end

  test 'from_hashstring works on array of symbols' do
    string = '{"abc" => [:test, 1, "abc"]}'
    assert_equal ['test', 1, 'abc'], from_hashstring(string)['abc']
  end