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Write ruby code to
change ruby code
Richard Huang
Xinmin Labs
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About Me
Founder at Xinmin Labs
Full Stack Developer
Open Source Enthusiast
@flyerhzm
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Problem
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Hey, let’s use rspec new syntax for project A
Yes, sure, I love the rspec new syntax
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Hey, let’s use rspec new syntax for project B
Hmmm…ok
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Hey, let’s use rspec new syntax for project C
Oh, no, I don’t want to repeat it again
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Developers love upgrading
and refactoring code
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Developers hate changing
code again and again
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Automation
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Metric Tools
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Metric Tools
• cane - fails your build if code quality thresholds
are not met
• reek - is a tool that examines Ruby classes,
modules and methods and reports any code
smells it finds.
• rails_best_practices - is a tool to check the quality
of rails code.
• ……
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Tell you what to do,
but can’t do for you
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IDE
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IDE
• can rename class / method / variable name
• can extract methods
• can ……
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IDE
• can’t customize
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Based on text
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Based on text
Replace FactoryGirl.create with create
!
$ sed -i '' 's/FactoryGirl.create/create/g' spec/**/*.rb
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Based on text
Replace FactoryGirl.create with create
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!
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Based on text
Hard to be accurate
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Based on text
Hard to convert complicated cases
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Based on AST
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What’s AST
AST is short for Abstract Syntax Tree
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What’s AST
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Why AST
It is much more accurate to parse ruby code.
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How to use AST
• ripper
• ParseTree - https://github.com/seattlerb/parsetree
• ruby_parser - https://github.com/seattlerb/ruby_parser
• parser - https://github.com/whitequark/parser
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How to use AST
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Example
transpec - https://github.com/yujinakayama/
transpec
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Based on AST
Accurate, but hard to write and read
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Synvert
https://github.com/xinminlabs/synvert
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Demo
http://xinminlabs.github.io/synvert/
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Synvert
• Add useful attributes to AST nodes
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• Provide DSL to parse and rewrite code
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Attributes for AST node
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Attributes for AST node
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Attributes for AST node
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Attributes for AST node
Check out more attributes
http://xinminlabs.github.io/synvert/rules/
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DSL
• within_file / within_files
• with_node / within_node
• if_exist_node / unless_exist_node
• append / insert / insert_after / replace_with /
remove
• ……
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DSL
Check out more DSL
http://xinminlabs.github.io/synvert/dsl/
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Playground
http://synvert-tools.herokuapp.com/
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Snippets
https://github.com/xinminlabs/synvert-snippets
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Want more?
• Fork and send pull request
• Open issues on github
• Hire us to refactor your project
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Q&A
!
Thank you