What is Stripe?

Stripe is a software platform for running a business online.

🔎 About Stripe

• More than 2,000 employees

• Engineers in San Francisco, Seattle, Dublin, Singapore, and more...

• We're hiring! (interns and full time)

🚀 Developer Productivity at Stripe

• "Break down obstacles to getting things done"

• Let our engineers focus on product

Stripe uses Ruby extensively 💎

• Ruby is our primary programming language

• Hundreds of engineers

• Millions of lines of code (monorepo)

• Thousands of changes to the monorepo per day

🗣 What problems did we have?

Responses from biannual eng-wide survey:

1. Too long to get feedback

2. Too long to grasp unfamiliar code

3. Too easy to accidentally break things

➡️ What are our options?

• Do nothing: Opportunity cost (productivity, breakages)

• Treat the symptoms of existing code: New symptoms pop up

• Rewrite everything: 100s of engineers, all-or-nothing

• Rewrite some things: 10s(?) of engineers, partial impact

• Type checker: 3 engineers, incremental value in months

➡️ What are our options?

• Do nothing: Opportunity cost (productivity, breakages)

• Treat the symptoms of existing code: New symptoms pop up

• Rewrite everything: 100s of engineers, all-or-nothing

• Rewrite some things: 10s(?) of engineers, partial impact

• Type checker: 3 engineers, incremental value in months

...our answer: Sorbet 🎉

• Oct 2017 – Kickoff

• Feb 2018 – First typed code

• June 2018 – Enforced in CI for every Stripe engineer

• ... lots of other stuff ...

• Jun 2019 – Open source!

The problems we wanted Sorbet to solve

1. Too long to grasp unfamiliar code

2. Too long to get feedback

3. Too easy to accidentally break things

1. Too long to grasp unfamiliar code

def self.find_card_similarity(merchant:)

  similarity_data = SimilarityDB.fetch(merchant)

  similarity_data ||= []

  process_similarity_data(similarity_data, merchant)
end

Hundreds of engineers means ~all code is unfamiliar

1. Too long to grasp unfamiliar code

def self.find_card_similarity(merchant:)
  # Is `merchant` a string ID, or a Models::Merchant instance?
  similarity_data = SimilarityDB.fetch(merchant)

  similarity_data ||= []

  process_similarity_data(similarity_data, merchant)
end

Hundreds of engineers means ~all code is unfamiliar

1. Too long to grasp unfamiliar code

def self.find_card_similarity(merchant:)
  # Is `merchant` a string ID, or a Models::Merchant instance?
  similarity_data = SimilarityDB.fetch(merchant)
  # Is `similarity_data` ever actually falsy? Why?
  similarity_data ||= []

  process_similarity_data(similarity_data, merchant)
end

Hundreds of engineers means ~all code is unfamiliar

2. Too long to get feedback

• All tests, locally: days
• All tests, in CI: 10 – 20 minutes
• One keystroke: ~50 milliseconds

Already have massively parallel distributed CI test runner

3. Too easy to break things

def self.find_card_similarity(merchant:)
  # Is `merchant` a string ID, or a Models::Merchant instance?
  similarity_data = SimilarityDB.fetch(merchant)
  # Is `similarity_data` ever actually falsy? Why?
  similarity_data ||= []

  process_similarity_data(similarity_data, merchant)
end

"I want to change this code!"

... is it enough if the tests pass?

... is it enough if the QA / canary deploys have no errors?

🤔 Does Sorbet fix these things?

Recap: Key benefits of Sorbet 💡

1. Too long to grasp unfamiliar code
   • → Types make code easier to grasp
2. Too long to get feedback
   • → Sorbet is as fast as you can type
3. Too easy to accidentally break things
   • → One more tool to reduce brittle code

🎉 Ruby 3 & Types!

• Ruby 3 stdlib will ship with type definitions.

• We're collaborating closely with the Ruby core team

• See more details in talks by Matz, Yusuke Endoh and us @ RubyKaigi 2019

Contributions 📈

• 1,100 pull requests commits since open source

• 152 total contributors

  • 10: current / former sorbet team
  • 36: Stripe employees
  • 106: non-Stripe employees

Gem support

• 117 pull requests: types for Ruby stdlib

• 203 pull requests: types for gems

• 34 external contributors to sorbet-typed

  • 85% of commits from community contributors!

Related projects

• sorbet-rails
  • All-in-one support for Rails with Sorbet
• Sord
  • Generates Sorbet types from YARD annotations
• Parlour
  • Framework for writing Sorbet plugins

What people say

What's next? 🚀

• Make it even faster

• Implement most-needed language features

• Invest heavily in editor tools (open source soon!)

Try Sorbet today! 🎊

sorbet.run

Thank you!