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This is a Ruby implementation of the KDL Document Language


Add this line to your application's Gemfile:

gem 'kdl'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install kdl


require 'kdl'

KDL.parse_document(a_string) #=> KDL::Document

You can optionally provide your own type annotation handlers:

KDL.parse_document(a_string, type_parsers: {
  'foo' => -> (value, type) {, type: type)

The foo proc will be called with instances of Value or Node with the type annotation (foo).

Parsers are expected to have a call method that takes the Value or Node, and the type annotation itself, as arguments, and is expected to return either an instance of Value or Node (depending on the input type) or nil to return the original value as is. Take a look at the built in parsers as a reference.


After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to


Bug reports and pull requests are welcome on GitHub at


The gem is available as open source under the terms of the MIT License.