The newsletter of RBS updates RubyKaigi Takeout 2021🍔💨 Sep. 10th

pp self ● Masataka Pocke Kuwabara ● Software Engineer at Bit Journey, Inc. ○ Developing Kibela, an information sharing tool. https://kibe.la ● A maintainer of RBS ● A CRuby committer since Mar. 2021 ← NEW!

First, Thanks for all RBS contributors!👏👏 AaronC81, Adrian-Hirt, Afront, CariWest, HoneyryderChuck, MITSUBOSHI, Morriar, PanosCodes, YutaGoto, Yuuki77, a2ikm, ahazem, aikyo02, alts, andrewmcodes, berkos, cky, connorshea, donaldong, duderman, floor114, guillaumebriday, hanachin, hargoniX, hjwylde, hsbt, jeremyevans, jocmp, johansenja, k0kubun, kachick, kddnewton, kmizu, ko1, ksss, kunitoo, kyanny, linhpham, mame, marcandre, masahito1997, meganemura, mihyaeru21, mtsmfm, natsuokawai, nobu, ochaochaocha3, ohbarye, palkan, pocke, pointlessone, raosush, s4na, satoryu, sbeckeriv, soutaro, south37, szTheory, tadd, taki, waka, wat-aro, ybiquitous, ykpythemind, ysakasin note: ascii order, (..Time.parse('2020-08-20').cover?(contributed_at) full list: https://github.com/ruby/rbs/graphs/contributors and https://github.com/ruby/gem_rbs_collection/graphs/contributors

Goal ● You get hints to introduce RBS to your application ● Announce RBS updates for Ruby 3.1 ○ RBS v2 will be released for Ruby 3.1

Support page This talk is pre-recording, so it may have updates between recording and event date. I wrote the additional information into the following GitHub repository. https://github.com/pocke/rubykaigi-2021 And I’m watching this talk so feel free to ask me!

Agenda: RBS Updates ● Introduce RBS and related softwares ● New feature: rbs collection ○ The main topic! ● Language Updates (Thanks soutaro-san!) ○ Bounded type parameter ○ Generic type aliases ● Other updates ○ Signature updates ○ Performance Improvements

Introduce RBS and related softwares

What’s is RBS? ● RBS is a language to describe Ruby types. ● It is a bundled gem since Ruby 3.0. ● You can also gem install rbs in Ruby 2.6+

Repositories RBS is developed under two GitHub repositories ● https://github.com/ruby/rbs ○ the rbs gem ○ rbs command, rbs library, and RBS files for Ruby builtin and stdlibs. ● https://github.com/ruby/gem_rbs_collection ○ RBS for 3rd party gems, such as rails, nokogiri, etc ○ Similar to DefinitelyTyped in TypeScript

Let’s contriubte to ruby/gem_rbs_collection ● It’s one of the easiest parts to contribute RBS ● We recommend writing gem RBS partially ○ RBS for gem’s all features is not required, focus the main features

Related softwares ● TypeProf: https://github.com/ruby/typeprof ○ A type analysis tool for Ruby code based on abstract interpretation ● Steep: https://github.com/soutaro/steep ○ Static Type Checker, using RBS ● RBS Rails: https://github.com/pocke/rbs_rails ○ RBS generator for Ruby on Rails ● Sorbet: https://github.com/sorbet/sorbet ○ Static Type Checker, using RBI (another language describes Ruby Type)

New feature: rbs collection

New feature: rbs colllection ● It manages dependent libraries’ RBSs ○ In short, Bundler for RBS ● I’m developing this feature ● rbs collection command has been released! ○ As experimental for now, it will be GA on RBS v2 ○ You can use it with gem install rbs now💎

Motivation Before rbs collection, managing libraries’ RBSs is not smart. Let’s look an example to prepare libraries’ RBSs for a Rails app

Motivating Example: Enable RBSs for a Rails app First, download gem_rbs_collection as git submodule $ git submodule add https://github.com/ruby/gem_rbs_collection.g it gem_rbs_collection

Motivating Example: Enable RBSs for a Rails app Then, rbs command is available with the following super many options! $ rbs -rlogger -rpathname -rmutex_m -rdate -rmonitor -rsingleton -rtsort -rtime --repo=gem_rbs_collection -rrack -ractivesupport -ractionpack -ractivejob -ractivemodel -ractionview -ractiverecord -rrailties validate

Motivating Example: Enable RBSs for a Rails app TypeProf needs the same options $ typeprof -rlogger -rpathname -rmutex_m -rdate -rmonitor -rsingleton -rtsort -rtime --repo=gem_rbs_collection -rrack -ractivesupport -ractionpack -ractivejob -ractivemodel -ractionview -ractiverecord -rrailties target.rb

Example: Enable RBSs for a Rails app (step 4) And, Steep needs another configuration file, Steepfile. target :app do signature 'sig' check 'app' repo_path "gem_rbs_collection" library 'pathname', 'logger', 'mutex_m', 'date', 'monitor', 'singleton', 'tsort', 'time', 'rack', 'activesupport', 'actionpack', 'activejob', 'activemodel', 'actionview', 'activerecord', 'railties' end

Conclusion of the motivations ● We need resolve dependencies by hand ○ The above examples, the human resolves “my app depends on Active Support, then Active Support depends on logger and …” ● To download, We need git submodule or copying RBSs ○ It’s too primitive. How controlling versions of 3rd party RBSs? ● To load, We need different ways between RBS, Steep, and TypeProf

rbs collection solves the problems!

What’s rbs collection? ● rbs collection is a command to manage libraries’ RBSs ● It does the following things ○ Resolve dependencies automatically ○ Download necessary RBSs ○ Load RBSs from one configuration file

Usage example: rbs collection for a Rails app First, you need to generate the configuration file, rbs_collection.yaml # to install the latest version of RBS $ gem install rbs $ rbs collection init created: rbs_collection.yaml

Usage example: rbs collection for a Rails app Then, edit the generated config file, add the following line + gems: [name: pathname, name: logger, name: mutex_m, name: date, name: monitor, name: singleton, name: tsort, name: time, name: set] (I’ll describe meaning of this diff)

Usage example: rbs collection for a Rails app Then install RBSs. Note that rbs collection needs Gemfile.lock to resolve the dependencies $ vim Gemfile && bundle install $ rbs collection install

Usage example: rbs collection for a Rails app Finally you can use RBS related tools without CLI options! $ rbs validate $ typeprof target.rb $ steep init && steep check Everything is going well! (NOTE: Steep and TypeProf haven’t been implemented yet maybe)

Mechanism of rbs collection

Mechanism of rbs collection ● It resolves dependencies with Gemfile.lock, and writes them to the lockfile, rbs_collection.lock.yaml ● It copies libraries’ RBSs with the lockfile from the sources, ruby/gem_rbs_collection GitHub repo in most cases. ● It loads RBSs with the lockfile for rbs, typeprof, steep commands.

Known Issue ● rbs collection doesn’t resolve dependencies of standard libraries ○ For example, logger, optparse, etc… ○ Because standard libraries don’t need to be added to gemspec/Gemfile in order to require. ● I’ll fix this problem soon by introducing a configuration file, such as manifest.yaml to each gem

New feature: Bounded Type Parameters

Bounded Type Parameters RBS v2 will introduce Bounded Type Parameters. It allows you to specify an upper bound to Type Parameters.

Motivating Example: PrettyPrint class ● The first parameter of PrettyPrint.new is the destination of printing. ○ e.g. PrettyPrint.new(str) ○ The output is given with << method

Motivating Example: PrettyPrint classs PrettyPrint.new("") # OK (String#<<) PrettyPrint.new(STDOUT) # OK (IO#<<) PrettyPrint.new([]) # OK (Array#<<) PrettyPrint.new(true) # Error (No TrueClass#<<) PrettyPrint.new(3) # Error (Integer#<< doesn't accept String)

Without bounded type parameters # RBS class PrettyPrint attr_reader output: _PPOut def initialize: (?_PPOut output) -> void end interface _PPOut def <<: (String) -> void end # Ruby PrettyPrint.new("") .output.size # _PPOut doesn't have #size PrettyPrint.new([]) .output.join("") # _PPOut doesn't have #join

Bounded type parameters solve this problem # RBS class PrettyPrint[X < _PPOut] attr_reader output: X def initialize: (?X output) -> void end interface _PPOut def <<: (String) -> void end # Ruby PrettyPrint.new("") .output.size # X == String, String#size exists PrettyPrint.new([]) .output.join("") # X == Array, Array#join exists

New feature: Generic Type Aliases

Generic Type Aliases RBS v2 will introduce generic type aliases.

Motivating Example: defining tree types type int_tree = { value: Integer, left: int_tree?, right: int_tree? } type string_tree = { value: String, left: string_tree?, right: string_tree? } We need to define the most same types for each type.

Generic Type Aliases solve this problem type tree[T] = { value: T, left: tree[T]?, right: tree[T]? } type int_tree = tree[Integer] type string_tree = tree[String] type cat_tree = tree[Cat] We can define generic tree[T] type to make them DRY!

Other updates

Other updates ● Signature updates ○ 80 RBS files added/updated since RBS v1 for Ruby 3.0 ● Performance Improvements ○ rbs validate command has been 3x faster than RBS v1 ○ Parsing RBS will be 5x faster by an RBS parser written in C by soutaro-san ● Many bug fixes See the CHANGELOG for full changes! https://github.com/ruby/rbs/blob/master/CHANGELOG.md

Conclusion

Conclusion ● RBS v2 will introduces many new features, such as rbs collection and language updates ● It also includes signature updates, performance improvements ● We’re developing RBS for Ruby v3.1! Thanks for listening!