RubyConf 2021

1. Enjoy Ruby Programming
in IDE and TypeProf
Yusuke Endoh (@mametter)
RubyConf 2021

2. Yusuke Endoh / @mametter
•A Ruby committer working at Cookpad w/ @ko1
•Main contribution so far:
• Designed and implemented keyword arguments
• Implemented test coverage feature
• Implementing TypeProf  Today's topic
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3. A recent contribution: error_highlight
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json = { foo: { bar: { baz: 42 } } }
json[:foo][:barr][:baz]
# Ruby 3.0
$ ruby t.rb
t.rb:2:in `<main>': undefined method `[]' for nil:NilClass (NoMethodError)
# Ruby 3.1
$ ruby t.rb
t.rb:2:in `<main>': undefined method `[]' for nil:NilClass (NoMethodError)
json[:foo][:barr][:baz]
^^^^^^
Credit: The original author of its prototype is @yui-knk
https://github.com/ruby/ruby/pull/4470

4. Index
•What is TypeProf?
•TypeProf for IDE
•How to use TypeProf for IDE
•Conclusion
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5. TypeProf: A static analyzer for Ruby 3
•TypeProf analyzes non-annotated Ruby code
• guess types of method arguments and a return value
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class User
def initialize(name)
@name = name
end
end
User.new("John")
Ruby code
class User
def initialize:(String name)->void
end
RBS
TypeProf

6. TypeProf? RBS? Steep? Sorbet?
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Name What
RBS
TypeProf
Steep
Sorbet
The Ruby official type definition language
A static type analyzer for Ruby
A static type analyzer for Ruby
A static type analyzer for Ruby

7. Comparison between static analyzers
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TypeProf Steep Sorbet
Type inference Strong Weak Weak
Accuracy Weak Strong Strong
Analysis speed Slow Fast Very fast
RBS support Yes Yes Not yet
IDE support No → Yes Yes Yes

8. RBS: An official language for Ruby types
• Common complaint: "Header files suck"
• TypeProf for IDE may solve this issue
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class User
def initialize(name)
@name = name
end
end
User.new("John")
user.rb
class User
def initialize:
(String name) -> void
end
user.rbs

9. Index
•What is TypeProf?
•TypeProf for IDE
•How to use TypeProf for IDE
•Conclusion
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10. Today's topic: TypeProf for IDE
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VSCode TypeProf
code changed
error found
complete "5.ti"
maybe "5.times"
5.ti|
Do you mean:
5.times
1 + "str"
1 + "str"
Is this a bug?
• A VSCode extension for Ruby powered by TypeProf

11. Demo: TypeProf for IDE
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12. The modern development experience
with TypeProf for IDE
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On-the-fly method signature

13. The modern development experience
with TypeProf for IDE
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On-the-fly error reporting

14. The modern development experience
with TypeProf for IDE
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15. The modern development experience
with TypeProf for IDE
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On-the-fly type inference
Completion

16. The modern development experience
with TypeProf for IDE
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Hint for arguments

17. Demo: Summary
•Modern development experience comes to Ruby
without type annotations
•RBS are interspersed to Ruby files
• One possible answer to "Header files suck"
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18. Index
•What is TypeProf?
•TypeProf for IDE
•How to use TypeProf for IDE
•Conclusion
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19. How to configure TypeProf for IDE
• Use ruby 3.1.0-dev (development version☺)
• Add for your Gemfile
• Configure RBS collection
• if you use gems
• Install VSCode extension→
• search "typeprof"
• Open your folder with VSCode and pray
• More detail: https://github.com/ruby/typeprof/blob/master/doc/ide.md
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gem "typeprof"

20. Protips™
•Write a simple test in a file
•Write RBS 😞
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21. Demo: Tests instead of type annotations
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untyped
String

22. Demo: Passing an unknown type
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The method signature is changed
to accept a new type
Error in the callee side

23. Demo: Manual RBS specification
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Click here
A prototype RBS is
created

24. Demo: Manual RBS specification (cont'd)
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Error in the caller side
# means RBS-defined

25. Protips™
•Write a simple test in a file
• TypeProf requires a test to guess method signatures
•Write RBS to fix method signatures (if needed)
• This makes TypeProf analysis faster
• This is also useful to make TypeProf faster
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26. Index
•What is TypeProf?
•TypeProf for IDE
•How to use TypeProf for IDE
•Conclusion
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27. Release plan
•TypeProf for IDE will be released in Ruby 3.1
• Happy if you could play with it and give us feedback
•Ready for production?
• Experimental, but hopefully works for small programs
• For large code base, please write RBS for gems first!
• https://github.com/ruby/gem_rbs_collection
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28. Special thanks
•Hideki Miura
•Ruby committers: matz, akr, ko1, soutaro
•Katsuhiro Ueno & Eijiro Sumii
•Stripe team & Shopify team & Jeff Foster
•Yuta Saito (@kateinoigakukun)
• Many improvements of TypeProf for IDE
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29. Conclusion
•The modern development experience is possible
without full type annotations by TypeProf for IDE
•Ruby 3.1 will bundle TypeProf for IDE
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