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https://github.com/ruby/rbs

Type Signature for Ruby
https://github.com/ruby/rbs

ruby type-checking

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Type Signature for Ruby

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README 

        
# RBS



RBS is a language to describe the structure of Ruby programs.

You can write down the definition of a class or module: methods defined in the class, instance variables and their types, and inheritance/mix-in relations.

It also allows declaring constants and global variables.



The following is a small example of RBS for a chat app.



```rbs

module ChatApp

  VERSION: String



  class User

    attr_reader login: String

    attr_reader email: String



    def initialize: (login: String, email: String) -> void

  end



  class Bot

    attr_reader name: String

    attr_reader email: String

    attr_reader owner: User



    def initialize: (name: String, owner: User) -> void

  end



  class Message

    attr_reader id: String

    attr_reader string: String

    attr_reader from: User | Bot                     # `|` means union types: `#from` can be `User` or `Bot`

    attr_reader reply_to: Message?                   # `?` means optional type: `#reply_to` can be `nil`



    def initialize: (from: User | Bot, string: String) -> void



    def reply: (from: User | Bot, string: String) -> Message

  end



  class Channel

    attr_reader name: String

    attr_reader messages: Array[Message]

    attr_reader users: Array[User]

    attr_reader bots: Array[Bot]



    def initialize: (name: String) -> void



    def each_member: () { (User | Bot) -> void } -> void  # `{` and `}` means block.

                   | () -> Enumerator[User | Bot, void]   # Method can be overloaded.

  end

end

```



## The Target Version



* The standard library signatures targets the latest release of Ruby. (`3.2` as of 2023.)

* The library code targets non-EOL versions of Ruby. (`>= 3.0` as of 2023.)



## Installation



Install the `rbs` gem. `$ gem install rbs` from the command line, or add a line in your `Gemfile`.



```rb

gem "rbs"

```



## CLI



The gem ships with the `rbs` command line tool to demonstrate what it can do and help develop RBS.



```console

$ rbs version

$ rbs list

$ rbs ancestors ::Object

$ rbs methods ::Object

$ rbs method Object then

```



An end user of `rbs` will probably find `rbs prototype` the most useful. This command generates boilerplate signature declarations for ruby files. For example, say you have written the below ruby script.



```ruby

# person.rb

class Person

  attr_reader :name

  attr_reader :contacts



  def initialize(name:)

    @name = name

    @contacts = []

  end



  def speak

    "I'm #{@name} and I love Ruby!"

  end

end

```



Running prototype on the above will automatically generate



```console

$ rbs prototype rb person.rb

class Person

  @name: untyped



  @contacts: untyped



  attr_reader name: untyped



  attr_reader contacts: untyped



  def initialize: (name: untyped) -> void



  def speak: () -> ::String

end

```



It prints signatures for all methods, classes, instance variables, and constants.

This is only a starting point, and you should edit the output to match your signature more accurately.



`rbs prototype` offers three options.



- `rb` generates from just the available Ruby code

- `rbi` generates from Sorbet RBI

- `runtime` generates from runtime API



## Library



There are two important concepts, _environment_ and _definition_.



An _environment_ is a dictionary that keeps track of all declarations. What is the declaration associated with `String` class? An _environment_ will give you the answer.



A _definition_ gives you the detail of the class. What is the type of the return value of `gsub` method of the `String` class? The _definition_ for `String` class knows the list of methods it provides and their types.



The following is a small code to retrieve the definition of the `String#gsub` method.



```rb

require "rbs"



loader = RBS::EnvironmentLoader.new()



# loader.add(path: Pathname("sig"))   # Load .rbs files from `sig` directory

# loader.add(library: "pathname")     # Load pathname library



environment = RBS::Environment.from_loader(loader).resolve_type_names



# ::String

string = RBS::TypeName.new(name: :String, namespace: RBS::Namespace.root)



# Class declaration for ::String

decl = environment.class_decls[string]



# Builder provides the translation from `declaration` to `definition`

builder = RBS::DefinitionBuilder.new(env: environment)



# Definition of instance of String

instance = builder.build_instance(string)



# Print the types of `gsub` method:

puts instance.methods[:gsub].method_types.join("\n")

# Outputs =>

#  (::Regexp | ::string pattern, ::string replacement) -> ::String

#  (::Regexp | ::string pattern, ::Hash[::String, ::String] hash) -> ::String

#  (::Regexp | ::string pattern) { (::String match) -> ::_ToS } -> ::String

#  (::Regexp | ::string pattern) -> ::Enumerator[::String, self]



# Definition of singleton of String

singleton = builder.build_singleton(string)

# No `gsub` method for String singleton

puts singleton.methods[:gsub]

```



## Guides



- [Architecture](docs/architecture.md)

- [Core and standard library signature contribution guide](docs/CONTRIBUTING.md)

- [Writing signatures guide](docs/sigs.md)

- [Stdlib signatures guide](docs/stdlib.md)

- [Syntax](docs/syntax.md)

- [RBS by Example](docs/rbs_by_example.md)

- [RBS collection](docs/collection.md)

- [Using `Data` and `Struct`](docs/data_and_struct.md)

- [Releasing a gem with RBS](docs/gem.md)



## Community



Here is a list of some places you can talk with active maintainers.



- [Ruby Discord Server (invite link)](https://discord.gg/ad2acQFtkh) -- We have `rbs` channel in Ruby Discord server.

- [ruby-jp Slack Workspace (in Japanese)](https://ruby-jp.github.io/) -- We have `types` channel in ruby-jp slack workspace.

- [gem_rbs_collection](https://github.com/ruby/gem_rbs_collection) -- We have a repository of third-party RBS type definitions, for the case your dependency doesn't ship with RBS files.



## Development



After checking out the repo, run `bin/setup` to install dependencies. Then, run `bundle exec 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 [rubygems.org](https://rubygems.org).



## Contributing



Bug reports and pull requests are welcome on GitHub at https://github.com/ruby/rbs.