Skip to content
Generate Sorbet RBIs from YARD documentation
Branch: master
Clone or download
Latest commit d9d88df Jul 21, 2019



Sord is a Sorbet and YARD crossover. It can automatically generate Sorbet type signatures files by looking at the types specified in YARD documentation comments.

If your project is already YARD documented, then this can generate most of the Sorbet signatures you need!

Sord has the following features:

  • Automatically generates signatures for modules, classes and methods
  • Support for multiple parameter or return types (T.any)
  • Gracefully handles missing YARD types (T.untyped)
  • Can infer setter parameter type from the corresponding getter's return type
  • Recognises mixins (include and extend)
  • Support for generic types such as Array<T> and Hash<K, V>
  • Can infer namespaced classes ([Bar] can become GemName::Foo::Bar)
  • Handles return types which can be nil (T.nilable)
  • Handles duck types (T.untyped)
  • Support for ordered list types ([Array(Integer, Symbol)] becomes [Integer, Symbol])
  • Support for boolean types ([true, false] becomes T::Boolean)
  • Support for &block parameters documented with @yieldparam and @yieldreturn


Install Sord with gem install sord.

Sord is a command line tool. To use it, open a terminal in the root directory of your project and invoke sord, passing a path where you'd like to save your .rbi (this file will be overwritten):

sord defs.rbi

Sord will generate YARD docs and then print information about what it's inferred as it runs. It is best to fix any issues in the YARD documentation, as any edits made to the resulting RBI file will be replaced if you re-run Sord.

RBI files generated by Sord can be used in two main ways:

Generally, you should ship the type signatures with your gem if possible. sorbet-typed is meant to be a place for gems that are no longer updated or where the maintainer is unwilling to ship type signatures with the gem itself.


Sord also takes some flags to alter the generated .rbi file:

  • --no-comments: Generates the .rbi file without any comments about warnings/inferences/errors.
  • --no-regenerate: By default, Sord will regenerate a repository's YARD docs for you. This option skips regenerating the YARD docs.
  • --break-params: Determines how many parameters are necessary before the signature is changed from a single-line to a multi-line block. (Default: 4)
  • --replace-errors-with-untyped: Uses T.untyped instead of SORD_ERROR_* constants.
  • --replace-unresolved-with-untyped: Uses T.untyped when Sord is unable to resolve a constant.
  • --include-messages and --exclude-messages: Used to filter the logging messages given by Sord. --include-messages acts as a whitelist, printing only messages of the specified logging kinds, whereas --exclude-messages acts as a blacklist and suppresses the specified logging kinds. Both flags take a comma-separated list of logging kinds, for example omit,infer. When using --include-messages, the done kind is included by default. (You cannot specify both --include-messages and --exclude-messages.)


Say we have this file, called test.rb:

module Example
  class Person
    # @param [String] name
    # @param [Integer] age
    # @return [Example::Person]
    def initialize(name, age)
      @name = name
      @age = age

    # @return [String] name
    attr_accessor :name

    # @return [Integer] age
    attr_accessor :age

    # @param [Array<String>] possible_names
    # @param [Array<Integer>] possible_ages
    # @return [Example::Person]
    def self.construct_randomly(possible_names, possible_ages), possible_ages.sample)

First, generate a YARD registry by running yardoc test.rb. Then, we can run sord test.rbi to generate the RBI file. (Careful not to overwrite your code files! Note the .rbi file extension.) In doing this, Sord prints:

[INFER] (Example::Person#name=) inferred type of parameter "value" as String using getter's return type
[INFER] (Example::Person#age=) inferred type of parameter "value" as Integer using getter's return type
[DONE ] Processed 8 objects

The test.rbi file then contains a complete RBI file for test.rb:

# typed: strong
module Example
  class Person
    sig { params(name: String, age: Integer).returns(Example::Person) }
    def initialize(name, age); end

    sig { returns(String) }
    def name(); end

    # sord infer - inferred type of parameter "value" as String using getter's return type
    sig { params(value: String).returns(String) }
    def name=(value); end

    sig { returns(Integer) }
    def age(); end

    # sord infer - inferred type of parameter "value" as Integer using getter's return type
    sig { params(value: Integer).returns(Integer) }
    def age=(value); end

    sig { params(possible_names: T::Array[String], possible_ages: T::Array[Integer]).returns(Example::Person) }
    def self.construct_randomly(possible_names, possible_ages); end

Things to be aware of

The general rule of thumb for type conversions is:

  • If Sord understands the YARD type, then it is converted into the Sorbet type.
  • If the YARD type is missing, Sord fills in T.untyped.
  • If the YARD type can't be understood, Sord creates an undefined Ruby constant with a similar name to the unknown YARD type. For example, the obviously invalid YARD type A%B will become a constant called SORD_ERROR_AB. You should search through your resulting RBI to find and fix and SORD_ERRORs.


Bug reports and pull requests are welcome on GitHub at This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

While contributing, if you want to see the results of your changes to Sord you can use the examples:seed Rake task. The task uses Sord to generate RBIs for a number of open source Ruby gems, including Bundler, Haml, Rouge, and RSpec. rake examples:seed (and rake examples:reseed to regenerate the RBI files) will clone the repositories of these gems into sord_examples/ and then generate the RBI files into the same directory.


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

Code of Conduct

Everyone interacting in the Sord project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.

You can’t perform that action at this time.