Have your Sorbet and eat it too

A short and sweet introduction to Sorbet, a type checker for Ruby. Learn how you can use types to write bulletproof code!

1. Have your Sorbet and eat it too !!!!!!!!!!!!!!! 9th September LRUG - @arkh4m
2. Hello! ! — My name is Ju — I work for NoRedInk — You can find me online as @arkh4m 9th September LRUG - @arkh4m 2
3. What is Sorbet? ! — Sorbet is a type checker designed for Ruby — It was built by Stripe and open sourced this year — You can find it at sorbet.org and play with it at sorbet.run 9th September LRUG - @arkh4m 3
4. Type checker you say? 9th September LRUG - @arkh4m 4
5. Different types of Type Systems — Dynamic type systems — Static type systems 9th September LRUG - @arkh4m 5
6. What To Know Before Debating Type Systems 9th September LRUG - @arkh4m 6
7. What are static types systems good for? 9th September LRUG - @arkh4m 7
8. 1. Correctness Imagine a world without NoMethodError: undefined method 9th September LRUG - @arkh4m 8
9. 2. Tooling Great refactoring support, since the computer knows more about the program. 9th September LRUG - @arkh4m 9
10. 3. Documentation Imagine a search engine where you say "Give me a function that takes a list of values, a function, an initial value and returns a result of the same type". It exists in Haskell and it's called Hoogle. 9th September LRUG - @arkh4m 10
11. 4. Performance Just like tooling, if the compiler knows more about the code, it can optimize it too. 9th September LRUG - @arkh4m 11
12. Does it actually work? 9th September LRUG - @arkh4m 12
13. NoRedInk — 420'000 lines of Elm in production — 30 engineers working in the team — Almost no runtime exceptions 9th September LRUG - @arkh4m 13
14. Dropbox Once your project is tens of thousands of lines of code, and several engineers work on it, our experience tells us that understanding code becomes the key to maintaining developer productivity. Without type annotations, basic reasoning such as figuring out the valid arguments to a function, or the possible return value types, becomes a hard problem. 9th September LRUG - @arkh4m 14
15. Dropbox A type checker solves this problem by providing a formal language for describing types, and by validating that the provided types match the implementation. In essence, it provides verified documentation. 9th September LRUG - @arkh4m 15
16. Ok, show me the code 9th September LRUG - @arkh4m 16
17. A simple example 9th September LRUG - @arkh4m 17
18. # typed: true class Kitten extend T::Sig sig {params(x: Integer).returns(String)} def jump(x) "The kitten jumps #{x} times." end end Try it 9th September LRUG - @arkh4m 18
19. If we wrote Kitten.new.jump(7) Sorbet would tell us No errors! Great job. 9th September LRUG - @arkh4m 19
20. But if we wrote Kitten.new.jump("10") 9th September LRUG - @arkh4m 20
21. We would get editor.rb:12: Expected Integer but found String("10") for argument x https://srb.help/7002 12 |Kitten.new.jump("10") ^^^^^^^^^^^^^^^^^^^^^ editor.rb:6: Method Kitten#jump has specified x as Integer 6 | sig {params(x: Integer).returns(String)} ^ Got String("10") originating from: editor.rb:12: 12 |Kitten.new.jump("10") ^^^^ Errors: 1 9th September LRUG - @arkh4m 21
22. Or if we wrote Kitten.new.jumps("10") 9th September LRUG - @arkh4m 22
23. We would get editor.rb:12: Method jumps does not exist on Kitten https://srb.help/7003 12 |Kitten.new.jumps("10") ^^^^^^^^^^^^^^^^^^^^^^ Autocorrect: Use `-a` to autocorrect editor.rb:12: Replace with jump 12 |Kitten.new.jumps("10") ^^^^^ Errors: 1 9th September LRUG - @arkh4m 23
24. How can I use Sorbet? 1. srb command line tool. Analyzes the code statically to report potential mistakes in the code. 2. sorbet-runtime gem. This gem will add methods that will also check the code dynamically while it runs. 9th September LRUG - @arkh4m 24
25. One magic comment to rule them all 9th September LRUG - @arkh4m 25
26. # typed: ignore The file is not even read by sorbet. 9th September LRUG - @arkh4m 26
27. # typed: false Errors related to syntax, constant resolution and correctness of signatures. 9th September LRUG - @arkh4m 27
28. # typed: true Calling a non-existant method, calling a method with mismatched arguments, using variables which are inconsistent with their types. 9th September LRUG - @arkh4m 28
29. # typed: strict All methods must have signatures and all variables must have explicitly annotated types. 9th September LRUG - @arkh4m 29
30. # typed: strong Values cannot be markes as untyped, which means the file is 100% statically typed. 9th September LRUG - @arkh4m 30
31. DEMO TIME! 9th September LRUG - @arkh4m 31
32. Thank you! Some interesting reads — What To Know Before Debating Type Systems — Our journey to type checking 4 million lines of Python — Type Checking in Ruby — Check Yo Self Before You Wreck Yo Self — A plan towards Ruby 3 Types, Yusuke Endoh 9th September LRUG - @arkh4m 32