All About RuboCop (Saint P RubyConf)

Slide-deck from my talk at the Saint P RubyConf 2018 in Saint Petersburg, Russia.

Transcript

2. Привет, ребята!
3. Божидар
4. Божo cool
5. (The RuboCop Guy)
6. Sofia, Bulgaria Sofia, Bulgaria
8. Bulgarian Cheese
9. Болгарка
10. Слънчев Бряг
11. Златни пясъци
12. Банско
15. Grigor Dimitrov vs Andrey Rublev
17. Lukanka
18. Rakia Connecting People
19. Shopska Salad (use only with Rakia)
21. bbatsov
22. Ruby & Rails style guides
27. First time in SPB!!!
32. #RubyKaraoke
33. Много городов у нас в России, Нету пальцев столько на ногах,
34. С каждым годом всё они красивей, Утопают в солнце и в снегах.
35. В Ростове шикарные плюхи, Размером с большую печать,
36. В Москве оху*тельно нюхать,
37. В Челябинске лучше торчать.
38. А в Питере…
41. All About RuboCop by Bozhidar Batsov (a.k.a. bug)
42. rubocop.readthedocs.io
43. Something About RuboCop by Bozhidar Batsov (a.k.a. bug)
44. RuboCop in a Nutshell
45. A Ruby static code analysis tool aimed to enforce the Ruby Community Style Guide
46. In other words…
47. It keeps your codebase consistent
48. It saves you time
49. It advances the Ruby language forward
51. 32,608,128
52. Provides an efficient way for codebases to be updated
53. Disclaimer
54. Lint tools are not a replacement for common sense
55. Why an entire talk about a mere lint tool?
58. 314 open issues
59. 100 volunteers
60. 3.14 issues/person
61. Coincidence?
62. Or providence?
63. A Brief History of Time
64. A Brief History of RuboCop
65. 2011 The Ruby Style Guide
67. May, 2012 RuboCop 0.0.0
68. May, 2012 RuboCop 0.0.0
70. Static code analysis with regular expressions …
72. Nov, 2012 Along Came Jonas
75. Spring, 2013 Return of the Jedi
76. Using a proper parser!
78. Struggles with Ripper
79. Ripper supported only MRI
80. I wanted to build a cross-platform tool
81. Ripper had (has?) almost no documentation
82. Ripper is tied to the underlying Ruby runtime
83. …which means you can’t parse code as Ruby 2.3 while running Ruby 2.5
84. Ripper has a very hard to work with AST representation
85. pry(main)> Ripper.sexp('alias :some :test') => [:program, [[:alias, [:symbol_literal, [:symbol, [:@ident, "some", [1, 7]]]], [:symbol_literal, [:symbol, [:@ident, "test", [1, 13]]]]]]]
86. 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
87. And many quirks…
88. 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"]]
89. 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, ")"]]
90. Which no one really considered problematic…
93. Parser: A New Hope From Russia with Love
94. parser is cross-platform
95. well documented
96. supports multiple parsing targets (Ruby 1.9 - 2.5)
98. easy to work with ast format https://github.com/whitequark/ast
99. p Parser::CurrentRuby.parse("2 + 2") # (send # (int 2) :+ # (int 2))
100. AST node source location mappings
101. 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 # "+"
102. $ 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
103. powerful code rewriting capabilities
105. Struggles with Parser
106. Parser was brand new
107. Had no real users
108. And had plenty of bugs…
110. Peter Zotov (@whitequark)
111. 28th May, 2013 State of Unity
112. RuboCop 0.8
113. 1st July, 2013 RuboCop 0.9
114. Formatters
115. Auto-correct
117. Commissioner (single parsing run triggers all cops)
118. Results caching (rubocop —-cache)
119. Parallel Checks (rubocop —-parallel)
120. Pattern Matching (regex-style matching for ast nodes)
121. 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)
122. Style/ArrayJoin (now) def_node_matcher :join_candidate?, '(send $array :* $str)' def on_send(node) join_candidate?(node) { add_offense(node, location: :selector) } end
123. RuboCop Today
124. Started out with no configuration at all…
125. Today things are infinitely configurable
126. Metrics/LineLength: Enabled: false
127. Metrics/LineLength: Max: 100
128. Style/StringLiterals: Enabled: false
129. Style/StringLiterals: EnforcedStyle: double_quotes
130. You can set a target Ruby/Rails version
131. You can limit cops to certain folders with Exclude/Include directives
132. You can have different settings for the same cops in different directories
133. You can inherit between configuration files
134. You can auto-generate an initial configuration for your project
135. rubocop —-auto-gen-config
136. And you can read about all of this in RuboCop’s manual…
137. rubocop.readthedocs.io
138. gry is a smarter alternative to the built-in command https://github.com/pocke/gry
139. RuboCop started as a code style checker
140. •Style •Lint •Layout •Naming •Security •Performance •Performance •Rails •Bundler •Metric •Gemspec
141. RuboCop is a great code formatter
142. rubocop —-only Layout -a
143. RuboCop does some linting better than ruby -w
144. rubocop —-lint
145. You can extend RuboCop with your own cops
146. Granite (business actions architecture for Rails applications) https://toptal.github.io/granite/
147. $ bundle exec rake new_cop[Department/Name]
148. https://rubocop.readthedocs.io/ en/latest/development/
149. 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
150. RuboCop has a rich ecosystem of extensions
153. 189!!!
154. Notable Extensions • rubocop-rspec • guard-rubocop • rubocop-sequel • rubocop-cask
155. Integration with code quality services •Code Climate •HoundCI •SideCI •Codacy
156. RuboCop has integrations with many editors and IDEs
157. Emacs 26.1 is out and it’s amazing!
158. (spacemacs)
159. The Road to RuboCop 1.0
160. #1 question I get asked about RuboCop?
161. When is RuboCop 1.0 coming?
162. “Using RuboCop is exciting. You never know if —auto-correct is going to work or not!” — Dick Sutterer
163. RuboCop changed my life! I used to go to horror movies to get an adrenaline rush - now I simply upgrade RuboCop! — Anton Devilov
164. RuboCop’s learning curve is amazing! I’m still amazed it never ends! — Aaron Punisherson (@hardlove)
165. “When faced with overwhelming odds just release 1.0 and it will all be OK!”
166. Remove Rails (and maybe Performance) cops from RuboCop’s core
167. Provide a proper (and stable) API for writing RuboCop extensions
168. Introducing the brand new RuboCop HQ!
169. https://github.com/bbatsov/rubocop
170. https://github.com/rubocop-hq/rubocop
171. 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)
172. Review the config of all cops and come up with the best defaults
173. Ideally each default should be backed by solid data/rationale
174. Adjust the list of enabled by default cops
175. Come up with a less painful process for dealing with new cops and configuration changes
176. mry makes RuboCop upgrades less painful https://github.com/pocke/mry
177. Agree on what’s going to be constituting breaking changes down the road
178. Breaking changes •Cop API changes •Extension API changes •Dropping support for Ruby versions •Renaming/removing cops •Renaming/changing/removing config values
179. Cop status “New” in minor releases
180. Cop status gets changed to Enabled/Disabled in major releases
181. Extra Cop metadata •Version added •Version default config changed •Version deprecated
182. eslint.org-grade manual/website
183. 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
185. That’s a lot of work!
186. Apes Together Strong!
187. Rubyists Together Strong!
188. Felina
189. Thanks! twitter: @bbatsov github: @bbatsov http//batsov.com http://emacsredux.com Saint P RubyConf Saint Petersburg, Russia 10.06.2018