All About RuboCop (RubyKaigi 2018)

Slide deck from my talk at RubyKaigi 2018 in Sendai.

Transcript

1. Hello!
2. Божидар
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
14. Grigor Dimitrov vs Kei Nishikori
16. Lukanka
17. Bulgarian Cheese
18. Rakia Connecting People
19. Shopska Salad (use only with Rakia)
21. bbatsov
22. Ruby & Rails style guides
27. First time in Japan!!!
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
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?
52. Notable Japanese Contributors • Yuji Nakayama (@yujinakayama) • Masataka Kuwabara (@pocke) • Koichi Ito (@koic) • Yukihiro "Matz" Matsumoto (@matz) ;-)
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
65. May, 2012 RuboCop 0.0.0
66. May, 2012 RuboCop 0.0.0
68. Static code analysis with regular expressions …
70. Nov, 2012 Along Came Jonas
73. Spring, 2013 Return of the Jedi
74. Using a proper parser!
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…
91. Parser: A New Hope
92. parser is cross-platform
93. well documented
94. supports multiple parsing targets (Ruby 1.9 - 2.5)
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
103. Struggles with Parser
104. Parser was brand new
105. Had no real users
106. And had plenty of bugs…
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
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
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
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