Invitation to the dark side of Ruby
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RubyKaigi 2019 LT Introduction of Maccro, a macro post-processor for Ruby in Ruby. https://github.com/tagomoris/maccro
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Invitation to the dark side of Ruby
- 1. Invitation to the Dark Side of Ruby RubyKaigi 2019 LT Satoshi Tagomori (@tagomoris)
- 2. Satoshi Tagomori (@tagomoris) Fluentd, MessagePack-Ruby, Norikra, Woothee, ... Arm Ltd.
- 4. • Treasure Data acquired by Arm at 2018 • We're hiring! at Mountain View, Tokyo, Vancouver and Cambridge • RubyKaigi 2019 After Party Sponsor!
- 5. Invitation to the Dark Side of Ruby
- 6. "If you only knew 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?
- 9. More ActiveRecord Examples (1)
- 10. More ActiveRecord Examples (2)
- 11. More ActiveRecord Examples (3)
- 12. ?
- 13. MACRO
- 14. I NEVER introduce macro to Ruby.
- 15. MY NEW PRODUCT: MACRO POST PROCESSOR
- 16. MY-MACRO: REGISTER • Register rules 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 ON METHODS • 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 method source: • 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 • Less performance 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 only on 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 only on 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
- 30. DONEC QUIS NUNC Thank you! Join us! https://github.com/tagomoris/maccro https://rubygems.org/gems/maccro Let's play with macro together!
- 31. "Join me and I will complete your training." <<仲間になれ。修行を完成させてやる>> Thank you!