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Invitation to the dark side of Ruby
The document outlines a presentation by Satoshi Tagomori at RubyKaigi 2019, introducing a new macro post-processor for Ruby called 'maccro'. It describes its functionality to automate routine code conversions and the various applications of macros within Ruby, including limitations and compatibility with Ruby versions. The presentation emphasizes the potential of macros in enhancing Ruby's capabilities while inviting the audience to experiment with the tool.
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Invitation to the dark side of Ruby
- 1. Invitation to the Dark Sideof Ruby RubyKaigi 2019 LT Satoshi Tagomori (@tagomoris)
- 2. Satoshi Tagomori (@tagomoris) Fluentd,MessagePack-Ruby, Norikra, Woothee, ... Arm Ltd.
- 4. • Treasure Dataacquired by Arm at 2018 • We're hiring! at Mountain View, Tokyo, Vancouver and Cambridge • RubyKaigi 2019 After Party Sponsor!
- 5. Invitation to the Dark Sideof Ruby
- 6. "If you onlyknew the power of the dark side" <<暗黒面のパワーはすばらしいぞ>>
- 7. EXAMPLE: 1 <2 < 3 1 < 2 < 3 true < 3 undefined method `<' for true:TrueClass
- 8. EXAMPLE: 1 <2 < 3 RUBY: 1 < 2 && 2 < 3 Can we do this routine conversion automatically?
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- 14. I NEVER introducemacro to Ruby.
- 15. MY NEW PRODUCT: MACRO POSTPROCESSOR
- 16. MY-MACRO: REGISTER • Registerrules with "before" and "after" matchers • "before"/"after": code in Ruby, with DSL for code placeholders • Placeholders (N: integer, >= 1): • eN: expressions which returns a value or values • vN: a single value (e.g., variable, constant, literal, etc)
- 17. MY-MACRO: APPLY ONMETHODS • Macro rules applied to methods • manually: apply(ModName, ModName.method(:method_name) • automatically: using TracePoint (:end)
- 18. • Registered matchers: •replace placeholders w/ matcher nodes for RubyVM::AST::Node MY-MACRO: PREPARE(2) VCALL: e1 VCALL: e2 VCALL: e3 Matcher: e1 Matcher: e2 Matcher: e3 OPCALL: < OPCALL: < OPCALL: < OPCALL: < Matcher code e1 < e2 < e3 Placeholders Matcher tree
- 19. • Applied methods: •parsed into AST using RubyVM::AbstractSyntaxTree#of • get the source of the method #<UnboundMethod: Mod#foo> def foo(v) if bar(v) < 1 # ... elsif bar(v) == 1 # ... elsif 1 < bar(v) < 2 # ... else # ... end end MY-MACRO: MATCH TO METHOD
- 20. def foo(v) if bar(v)< 1 # ... elsif bar(v) == 1 # ... elsif 1 < bar(v) < 2 # ... else # ... end end • Matched tree: • get code snippets for matcher nodes • e1: 1 (literal) • e2: bar(v) (func call with v) • e3: 2 (literal) e1 < e2 < e3 Matcher: e1 Matcher: e2 Matcher: e3 MY-MACRO: REWRITE CODE (1)
- 21. • Matched tree: •replace patterns in "after" code with captured snippets • e1: 1 (literal) • e2: bar(v) • e3: 2 (literal) e1 < e2 && e2 < e3 "After" code 1 < bar(v) && bar(v) < 2 "After" code for this method "Before" code e1 < e2 < e3 MY-MACRO: REWRITE CODE (2)
- 22. • Matched tree: •rewrite original method code with updated "after" code def foo(v) if bar(v) < 1 # ... elsif bar(v) == 1 # ... elsif 1 < bar(v) < 2 # ... else # ... end end e1 < e2 && e2 < e3 "After" code 1 < bar(v) && bar(v) < 2 "After" code for this method "Before" code e1 < e2 < e3 Original code of this method MY-MACRO: REWRITE CODE (3)
- 23. • Matched tree: •rewrite original method code with updated "after" code 1 < bar(v) && bar(v) < 2 "After" code for this method def foo(v) if bar(v) < 1 # ... elsif bar(v) == 1 # ... elsif 1 < bar(v) && bar(v) < 2 # ... else # ... end end Updated code of this method e1 < e2 && e2 < e3 "After" code "Before" code e1 < e2 < e3 MY-MACRO: REWRITE CODE (3)
- 24. • Rewritten methodsource: • call Modue#module_eval to replace the method definition def foo(v) if bar(v) < 1 # ... elsif bar(v) == 1 # ... elsif 1 < bar(v) < 2 # ... else # ... end end def foo(v) if bar(v) < 1 # ... elsif bar(v) == 1 # ... elsif 1 < bar(v) && bar(v) < 2 # ... else # ... end end Overwrite the method definition by Module#module_eval MY-MACRO: REWRITE METHOD
- 25. NICE STUFFS • Lessperformance penalty • Macro processor works only when methods are defined • Ruby version independent Macro rules • Compatible between Ruby versions • Because of rules written in Ruby code • Built-in rules, useful for some cases • Continuous inequality operators (<=, <, >, >=) • ActiveRecord utilities
- 26. LIMITATIONS • Supported onlyon Ruby 2.6 or later • Only code in def in module/class are rewritable • Calling class method just after definition can't be updated • Same method can't be rewritten twice • Non-idempotent methods causes unexpected result • Updating Lambda and local variable name matching is not implemented yet • Stack trace of updated methods would be confusing • Source from STDIN or command line (and irb/pry) cause errors • Rule-order-dependent issues will be caused • Method visibility are not taken care right now • Non-self singleton method definition causes errors • Placeholder validations are not implemented yet
- 27. • Supported onlyon Ruby 2.6 or later • Only code in def in module/class are rewritable • Calling class method just after definition can't be updated • Same method can't be rewritten twice • Non-idempotent methods causes unexpected result • Updating Lambda and local variable name matching is not implemented yet • Stack trace of updated methods would be confusing • Source from STDIN or command line (and irb/pry) cause errors • Rule-order-dependent issues will be caused • Method visibility are not taken care right now • Non-self singleton method definition causes errors • Placeholder validations are not implemented yet LIMITATIONS Just Few Limitations
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- 30. DONEC QUIS NUNC Thankyou! Join us! https://github.com/tagomoris/maccro https://rubygems.org/gems/maccro Let's play with macro together!
- 31. "Join me andI will complete your training." <<仲間になれ。修行を完成させてやる>> Thank you!