All About RuboCop (RubyKaigi 2018)

Transcript

1. Hello!

2. Божидар

3. None

4. Bozhidar

5. Божo

6. Bozho cool

7. Bozo not cool

8. Bozho is not a bozo!

9. Bozho is not a bozo! (at least he claims so)

10. Bug cool

11. (The RuboCop Guy)

12. Sofia, Bulgaria Sofia, Bulgaria

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14. Grigor Dimitrov vs Kei Nishikori

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16. Lukanka

17. Bulgarian Cheese

18. Rakia Connecting People

19. Shopska Salad (use only with Rakia)

20. None

21. bbatsov

22. Ruby & Rails style guides

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27. First time in Japan!!!

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33. None

34. All About RuboCop by Bozhidar Batsov (a.k.a. bug)

35. Writing Lint for Ruby by Masataka Kuwabara (a.k.a. Pocke) http://rubykaigi.org/2017/presentations/p_ck_.html

36. Improve Ruby coding style rules and Lint by Koichi Ito

    http://rubykaigi.org/2018/presentations/koic.html#jun01

37. Something About RuboCop by Bozhidar Batsov (a.k.a. bug)

38. RuboCop in a Nutshell

39. A Ruby static code analysis tool aimed to enforce the

    Ruby Community Style Guide

40. In other words…

41. It keeps your codebase consistent

42. It saves you time

43. It advances the Ruby language forward

44. None

45. 32,608,128

46. Provides an efficient way for codebases to be updated

47. Disclaimer

48. Lint tools are not a replacement for common sense

49. Why an entire talk about a mere lint tool?

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51. None

52. Notable Japanese Contributors • Yuji Nakayama (@yujinakayama) • Masataka Kuwabara

    (@pocke) • Koichi Ito (@koic) • Yukihiro "Matz" Matsumoto (@matz) ;-)
53. None

54. https://github.com/rubocop-jp/issues

55. https://github.com/fortissimo1997/ruby-style-guide

56. 314 open issues

57. 100 volunteers

58. 3.14 issues/person

59. Coincidence?

60. Or providence?

61. A Brief History of Time

62. A Brief History of RuboCop

63. 2011 The Ruby Style Guide

64. None

65. May, 2012 RuboCop 0.0.0

66. May, 2012 RuboCop 0.0.0

67. None

68. Static code analysis with regular expressions …

69. None

70. Nov, 2012 Along Came Jonas

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73. Spring, 2013 Return of the Jedi

74. Using a proper parser!

75. None

76. Struggles with Ripper

77. Ripper supported only MRI

78. I wanted to build a cross-platform tool

79. Ripper had (has?) almost no documentation

80. Ripper is tied to the underlying Ruby runtime

81. …which means you can’t parse code as Ruby 2.3 while

    running Ruby 2.5

82. Ripper has a very hard to work with AST representation

83. pry(main)> Ripper.sexp('alias :some :test') => [:program, [[:alias, [:symbol_literal, [:symbol, [:@ident,

    "some", [1, 7]]]], [:symbol_literal, [:symbol, [:@ident, "test", [1, 13]]]]]]]

84. each(:method_add_arg, sexp) do |s| next if s[1][0] != :call receiver

    = s[1][1][1] method_name = s[1][3][1] if receiver && receiver[1] == 'Array' && method_name == 'new' && s[2] == [:arg_paren, nil] offences.delete(Offence.new(:convention, receiver[2].lineno, ERROR_MESSAGE)) add_offence(:convention, receiver[2].lineno, ERROR_MESSAGE) end end

85. And many quirks…

86. pry(main)> Ripper.lex(':one') => [[[1, 0], :on_symbeg, ":"], [[1, 1], :on_ident,

    "one"]] pry(main)> Ripper.lex(':alias') => [[[1, 0], :on_symbeg, ":"], [[1, 1], :on_kw, "alias"]]

87. pry(main)> Ripper.lex('def alias(arg)')
 => [[[1, 0], :on_kw, "def"],
 [[1, 3],

    :on_sp, " "],
 [[1, 4], :on_kw, "alias"],
 [[1, 9], :on_lparen, "("],
 [[1, 10], :on_ident, “arg"],
 [[1, 13], :on_rparen, ")"]] pry(main)> Ripper.lex('def aliass(arg)')
 => [[[1, 0], :on_kw, "def"],
 [[1, 3], :on_sp, " "],
 [[1, 4], :on_ident, "aliass"],
 [[1, 10], :on_lparen, "("],
 [[1, 11], :on_ident, "arg"],
 [[1, 14], :on_rparen, ")"]]

88. Which no one really considered problematic…

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91. Parser: A New Hope

92. parser is cross-platform

93. well documented

94. supports multiple parsing targets (Ruby 1.9 - 2.5)

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96. easy to work with ast format https://github.com/whitequark/ast

97. p Parser::CurrentRuby.parse("2 + 2") # (send # (int 2) :+

    # (int 2))

98. AST node source location mappings

99. p Parser::CurrentRuby.parse("2 + 2").loc # #<Parser::Source::Map::Send:0x007fe5a1ac2388 # @dot=nil, # @begin=nil,

    # @end=nil, # @selector=#<Source::Range (string) 2...3>, # @expression=#<Source::Range (string) 0...5>> p Parser::CurrentRuby.parse("2 + 2").loc.selector.source # "+"

100. $ ruby-parse -L -e "2+2" (send (int 2) :+ (int

     2)) 2+2 ~ selector ~~~ expression (int 2) 2+2 ~ expression (int 2) 2+2 ~ expression

101. powerful code rewriting capabilities

102. None

103. Struggles with Parser

104. Parser was brand new

105. Had no real users

106. And had plenty of bugs…

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108. Peter Zotov (@whitequark)

109. 28th May, 2013 State of Unity

110. RuboCop 0.8

111. 1st July, 2013 RuboCop 0.9

112. Formatters

113. Auto-correct

114. None

115. Commissioner (single parsing run triggers all cops)

116. Results caching (rubocop —-cache)

117. Parallel Checks (rubocop —-parallel)

118. Pattern Matching (regex-style matching for ast nodes)

119. def on_send(node) receiver_node, method_name, *arg_nodes = *node return unless receiver_node

     && receiver_node.array_type? && method_name == :* && arg_nodes.first.str_type? add_offense(node, location: :selector) end Style/ArrayJoin (before)

120. Style/ArrayJoin (now) def_node_matcher :join_candidate?, '(send $array :* $str)' def on_send(node)

     join_candidate?(node) { add_offense(node, location: :selector) } end

121. RuboCop Today

122. Started out with no configuration at all…

123. Today things are infinitely configurable

124. Metrics/LineLength: Enabled: false

125. Metrics/LineLength: Max: 100

126. Style/StringLiterals: Enabled: false

127. Style/StringLiterals: EnforcedStyle: double_quotes

128. You can set a target Ruby/Rails version

129. You can limit cops to certain folders with Exclude/Include directives

130. You can have different settings for the same cops in

     different directories

131. You can inherit between configuration files

132. You can auto-generate an initial configuration for your project

133. rubocop —-auto-gen-config

134. And you can read about all of this in RuboCop’s

     manual…

135. rubocop.readthedocs.io

136. gry is a smarter alternative to the built-in command https://github.com/pocke/gry

137. RuboCop started as a code style checker

138. •Style •Lint •Layout •Naming •Security •Performance •Performance •Rails •Bundler •Metric

     •Gemspec

139. RuboCop is a great code formatter

140. rubocop —-only Layout -a

141. RuboCop does some linting better than ruby -w

142. rubocop —-lint

143. You can extend RuboCop with your own cops

144. Granite (business actions architecture for Rails applications) https://toptal.github.io/granite/

145. $ bundle exec rake new_cop[Department/Name]

146. https://rubocop.readthedocs.io/ en/latest/development/

147. class SimplifyNotEmptyWithAny < Cop MSG = 'Use `.any?` and remove

     the negation part.'.freeze def_node_matcher :not_empty_call?, <<-PATTERN (send (send (...) :empty?) :!) PATTERN def on_send(node) return unless not_empty_call?(node) add_offense(node) end end

148. RuboCop has a rich ecosystem of extensions

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151. 189!!!

152. Notable Extensions • rubocop-rspec • guard-rubocop • rubocop-sequel • rubocop-cask

153. Integration with code quality services •Code Climate •HoundCI •SideCI •Codacy

154. RuboCop has integrations with many editors and IDEs

155. Emacs 26.1 is out and it’s amazing!

156. (spacemacs)

157. The Road to RuboCop 1.0

158. #1 question I get asked about RuboCop?

159. When is RuboCop 1.0 coming?

160. Remove Rails (and maybe Performance) cops from RuboCop’s core

161. Provide a proper (and stable) API for writing RuboCop extensions

162. Introducing the brand new RuboCop HQ!

163. https://github.com/bbatsov/rubocop

164. https://github.com/rubocop-hq/rubocop

165. RuboCop HQ •RuboCop •RuboCop JP •RuboCop RSpec/Rails/Performance •guard-rubocop, etc •Ruby

     & Rails Style Guides •Libraries extracted from RuboCop (e.g. node extensions, node pattern matching, etc)

166. Review the config of all cops and come up with

     the best defaults

167. Ideally each default should be backed by solid data/rationale

168. Adjust the list of enabled by default cops

169. Come up with a less painful process for dealing with

     new cops and configuration changes

170. mry makes RuboCop upgrades less painful https://github.com/pocke/mry

171. Agree on what’s going to be constituting breaking changes down

     the road

172. Breaking changes •Cop API changes •Extension API changes •Dropping support

     for Ruby versions •Renaming/removing cops •Renaming/changing/removing config values

173. Cop status “New” in minor releases

174. Cop status gets changed to Enabled/Disabled in major releases

175. Extra Cop metadata •Version added •Version default config changed •Version

     deprecated

176. eslint.org-grade manual/website

177. RuboCop.org •Easy to navigate & mobile-friendly •Published using MkDocs (or

     similar) •Separate User and Developer manual •Getter getting started resources (e.g. video tutorials) •Improved cop documentation
178. None

179. That’s a lot of work!

180. Apes Together Strong!

181. Rubyists Together Strong!

182. Felina

183. Thanks! twitter: @bbatsov github: @bbatsov http//batsov.com http://emacsredux.com RubyKaigi Sendai, Japan

     31.05.2018