All About RuboCop (RubyConf.by 2018)

Slide deck from my talk at RubyConf.by 2018 in Minsk.

Transcript

1. Hello!
2. Божидар
3. Божo
4. Sofia, Bulgaria Sofia, Bulgaria
5. Balkan Ruby @balkanruby https://balkanruby.com 25-26 May Sofia, Bulgaria
6. I love rakiya! And Sofia!
8. https://github.com/toptal/granite
9. bbatsov
10. Ruby & Rails style guides
15. All About RuboCop by Bozhidar Batsov (a.k.a. bug)
16. RuboCop in a Nutshell
17. A Ruby static code analysis tool aimed to enforce the Ruby Community Style Guide
18. In other words…
19. It keeps your codebase consistent
20. It saves you time
21. It advances the Ruby language forward
22. It doesn’t work very well…
23. foo.each
24. foo.each
25. 314 open issues
26. 100 volunteers
27. 3.14 issues/person
28. Coincidence?
30. And your code is still shit afterwards!
31. A prettier shit, but still - shit.
32. A Brief History of Time
33. A Brief History of RuboCop
34. 2011 The Ruby Style Guide
36. May, 2012 RuboCop 0.0.0
38. Static code analysis with regular expressions …
40. Nov, 2012 Along Came Jonas
43. Spring, 2013 Renewed push
44. Using a proper parser!
46. Struggles with Ripper
47. Ripper supported just MRI
48. I wanted to build a cross- platform tool
49. Ripper has a very hard to work AST representation
50. pry(main)> Ripper.sexp('alias :some :test') => [:program, [[:alias, [:symbol_literal, [:symbol, [:@ident, "some", [1, 7]]]], [:symbol_literal, [:symbol, [:@ident, "test", [1, 13]]]]]]]
51. 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
52. And many quirks…
53. 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"]]
54. 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, ")"]]
55. Which no one really considered problematic…
58. Parser: A New Hope
59. parser was cross-platform
60. well documented
62. easy to work with ast format
63. p Parser::CurrentRuby.parse("2 + 2") # (send # (int 2) :+ # (int 2))
64. node source location mappings
65. 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 # "+"
66. $ 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
67. powerful code rewriting capabilities
69. Struggles with Parser
70. Parser was brand new
71. Had no real users
72. And had plenty of bugs…
74. 28th May, 2013 State of Unity
75. RuboCop 0.8
76. 1st July, 2013 RuboCop 0.9
77. Formatters
78. Auto-correct
80. Commissioner (single parsing run triggers all cops)
81. Results caching (rubocop —-cache)
82. Parallel Checks (rubocop —-parallel)
83. Pattern Matching (regex-style matching for ast nodes)
84. 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)
85. Style/ArrayJoin (now) def_node_matcher :join_candidate?, '(send $array :* $str)' def on_send(node) join_candidate?(node) { add_offense(node, location: :selector) } end
86. RuboCop Today
87. 30,745,153
88. Started out with no configuration at all…
89. Today things are infinitely configurable
90. Metrics/LineLength: Enabled: false
91. Metrics/LineLength: Max: 100
92. Style/StringLiterals: Enabled: false
93. Style/StringLiterals: EnforcedStyle: double_quotes
94. You can limit cops to certain folders with Exclude/Include directives
95. You can have different settings for the same cops in different directories
96. You can set a target Ruby/Rails version
97. You can inherit between configuration files
98. You can auto-generate an initial configuration for your project
99. rubocop —-auto-gen-config
100. gry is smarter alternative of the built-in command https://github.com/pocke/gry
101. RuboCop started just as a code style checker
102. •Style •Lint •Layout •Naming •Security •Performance •Performance •Rails •Bundler •Metric •Gemspec
103. RuboCop is a great code formatter
104. rubocop —-only Layout
105. RuboCop does some linting better that ruby -w
106. rubocop —-lint
107. You can extend RuboCop with your own cops
108. https://rubocop.readthedocs.io/en/latest/ development/
109. $ bundle exec rake new_cop[Department/Name]
110. 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
111. RuboCop has a rich ecosystem of extensions
114. 189!!!
115. Notable Extensions • rubocop-rspec • guard-rubocop • rubocop-sequel • rubocop-cask
116. Integration with code quality services • Code Climate • HoundCI • SideCI • Codacy
117. RuboCop has integrations with many editors and IDEs
118. And you can read about all of this in RuboCop’s manual…
119. rubocop.readthedocs.io
120. mry makes RuboCop upgrades less painful https://github.com/pocke/mry
121. The Road to RuboCop 1.0
122. #1 question I get asked about RuboCop?
123. When is RuboCop 1.0 coming?
124. Remove Rails and Performance cops from RuboCop’s core
125. Provide a proper (and stable) API for writing RuboCop extensions
126. Review the config of all cops and come up with the best defaults
127. Adjust the list of enabled by default cops
128. Agree on what’s going to be constituting breaking changes down the road
129. Come up with a less painful process for dealing with new cops and configuration changes
130. That’s a lot of work!
131. Apes Together Strong!
132. Rubyists Together Strong!
133. Felina
134. Thanks! twitter: @bbatsov github: @bbatsov http//batsov.com http://emacsredux.com RubyConf BY Minsk, Belarus 21.04.2018