How GitHub uses linters

The GitHub code base is growing at over 25% every year through contributions from over 1000 engineers, clocking in at 1.7+ million lines of Ruby. In this talk, we'll share how we use linters to keep our codebase healthy by ensuring best practices are applied consistently, feedback loops are as short as possible, and code reviews bring the most value, all without creating too much friction.

Transcript

1. How GitHub uses linters @joelhawksley How GitHub uses linters
3. How GitHub uses linters @joelhawksley 1000+ Linters!
4. How GitHub uses linters @joelhawksley
5. How GitHub uses linters @joelhawksley 👋
6. @joelhawksley Joel Hawksley How GitHub uses linters @joelhawksley
9. How GitHub uses linters @joelhawksley How GitHub uses linters
10. How GitHub uses linters @joelhawksley Why
11. How GitHub uses linters @joelhawksley Examples
12. How GitHub uses linters @joelhawksley Lessons
13. How GitHub uses linters @joelhawksley ⚠
14. How GitHub uses linters @joelhawksley Context
15. How GitHub uses linters @joelhawksley >14 Years old
16. How GitHub uses linters @joelhawksley 1,000,000+ Commits
17. How GitHub uses linters @joelhawksley 2.5 million Lines of Ruby
18. How GitHub uses linters @joelhawksley 1,000+ Contributors to monorepo
19. How GitHub uses linters @joelhawksley Context
20. How GitHub uses linters @joelhawksley linter (n.) a static code analysis tool used to flag programming errors, bugs, stylistic errors and suspicious constructs.
21. How GitHub uses linters @joelhawksley linter (n.) Automated feedback on your code
22. How GitHub uses linters @joelhawksley Why
23. How GitHub uses linters @joelhawksley Scale
24. How GitHub uses linters @joelhawksley Consistent practices
25. How GitHub uses linters @joelhawksley Good feedback
26. How GitHub uses linters @joelhawksley Specific Timely Actionable
27. How GitHub uses linters @joelhawksley Specific Timely Actionable
28. How GitHub uses linters @joelhawksley Specific Timely Actionable
29. How GitHub uses linters @joelhawksley Examples
30. How GitHub uses linters @joelhawksley Nudges
31. How GitHub uses linters @joelhawksley 🕵 Sentinel
32. @ktravers Kate Travers How GitHub uses linters @joelhawksley
33. How GitHub uses linters @joelhawksley // Bad <!—- some message the public shouldn’t see —->
34. How GitHub uses linters @joelhawksley - id: html-comment title: HTML Comments pattern: - <!-- description: "This HTML comment will be rendered into the DOM at runtime, potentially [exposing sensitive information] (http://cwe.mitre.org/data/definitions/615.html) about the design/implementation of the application. Please consider removing it or converting it to an ERB comment instead, since ERB comments are stripped out when the template is compiled and have no effect at runtime."
36. How GitHub uses linters @joelhawksley - id: stylelint-rule-change title: Stylelint rule change description: 'Stylelint rule changes should be reviewed by @github/primer-reviewers' pattern: - (\/\/|\/\*)\s*stylelint\-disable request_review: - '@github/primer-reviewers'
37. How GitHub uses linters @joelhawksley - id: stylelint-rule-change title: Stylelint rule change description: 'Stylelint rule changes should be reviewed by @github/primer-reviewers' pattern: - (\/\/|\/\*)\s*stylelint\-disable request_review: - '@github/primer-reviewers'
38. How GitHub uses linters @joelhawksley Specific Timely Actionable
39. How GitHub uses linters @joelhawksley Specific Timely Actionable
40. How GitHub uses linters @joelhawksley Specific Timely Actionable
41. How GitHub uses linters @joelhawksley Linters as tests
42. How GitHub uses linters @joelhawksley Assertions about code
43. How GitHub uses linters @joelhawksley ~300 Linters as tests
44. @jonrohan Jon Rohan How GitHub uses linters @joelhawksley
45. How GitHub uses linters @joelhawksley /(whitelist|blacklist)/
46. How GitHub uses linters @joelhawksley def test_no_violations matches = grep( /(whitelist|blacklist)/, paths: PATHS ).lines assert_empty(matches) end
47. @aroben Adam Roben How GitHub uses linters @joelhawksley
48. How GitHub uses linters @joelhawksley assert_operator( grep(/\.html_safe[^_?]/).lines, :<=, ALLOWED_HTML_SAFE_COUNT, message )
49. How GitHub uses linters @joelhawksley assert_operator( grep(/\.html_safe[^_?]/).lines, :<=, ALLOWED_HTML_SAFE_COUNT, message )
50. How GitHub uses linters @joelhawksley # CODEOWNERS html_safe_test.rb @github/pipeline-reviewers
51. How GitHub uses linters @joelhawksley ALLOWED_HTML_SAFE_COUNT
52. How GitHub uses linters @joelhawksley COUNTER = 50
53. How GitHub uses linters @joelhawksley Branch A COUNTER = 45 Branch B COUNTER = 40
54. How GitHub uses linters @joelhawksley COUNTER = ?
55. How GitHub uses linters @joelhawksley Branch A Branch B Branch C Branch D COUNTER = 28 COUNTER = 39 COUNTER = 41 COUNTER = 42
56. @antn Antonio Diaz How GitHub uses linters @joelhawksley
58. How GitHub uses linters @joelhawksley BOXED_GROUP_VIEWS = %w( app/views/actions/_filter_input.html.erb … )
59. How GitHub uses linters @joelhawksley matches = grep( /boxed-group-*.*/, paths: %w[app/views/**/*.erb], ).lines
60. How GitHub uses linters @joelhawksley BOXED_GROUP_VIEWS & matches
61. How GitHub uses linters @joelhawksley BOXED_GROUP_VIEWS = %w( app/views/actions/_filter_input.html.erb … )
62. How GitHub uses linters @joelhawksley Specific Timely Actionable
63. How GitHub uses linters @joelhawksley Specific Timely Actionable
64. How GitHub uses linters @joelhawksley Specific Timely Actionable
65. How GitHub uses linters @joelhawksley Specific Timely Actionable
66. How GitHub uses linters @joelhawksley Abstract Syntax Trees
67. How GitHub uses linters @joelhawksley (n.): a tree representation of the abstract syntactic structure of text
68. How GitHub uses linters @joelhawksley AST
69. How GitHub uses linters @joelhawksley <% foo %> s(:document, s(:text, s(:erb, nil, nil, s(:code, " foo "), nil)))
70. How GitHub uses linters @joelhawksley <% foo %> s(:document, s(:text, s(:erb, nil, nil, s(:code, " foo "), nil)))
71. How GitHub uses linters @joelhawksley ~2 dozen Erb-linters
72. @khiga8 Kate Higa How GitHub uses linters @joelhawksley
73. How GitHub uses linters @joelhawksley <img … alt=“Image of person jumping in the air” />
74. How GitHub uses linters @joelhawksley <img … alt=“Image of person jumping in the air” /> “Image: Image of person jumping in the air”
75. How GitHub uses linters @joelhawksley class A11yNoRedundantImageAlt < Linter MESSAGE = "<img> alt attr should not contain `image` or `picture` as screen readers already announce the element as an image” REDUNDANT_ALT_WORDS = %w(image picture) end
76. How GitHub uses linters @joelhawksley class A11yNoRedundantImageAlt < Linter MESSAGE = "<img> alt attr should not contain `image` or `picture` as screen readers already announce the element as an image” REDUNDANT_ALT_WORDS = %w(image picture) def run(tag) next if tag.name != "img" if (tag.alt.downcase.split & REDUNDANT_ALT_WORDS).any? generate_offense(tag) end end end
77. How GitHub uses linters @joelhawksley class A11yNoRedundantImageAlt < Linter MESSAGE = "<img> alt attr should not contain `image` or `picture` as screen readers already announce the element as an image” REDUNDANT_ALT_WORDS = %w(image picture) def run(tag) next if tag.name != "img" if (tag.alt.downcase.split & REDUNDANT_ALT_WORDS).any? generate_offense(tag) end end end
78. How GitHub uses linters @joelhawksley ~125 Rubocops
79. @brasic Carl Brasic How GitHub uses linters @joelhawksley
80. How GitHub uses linters @joelhawksley GitHub.test? GitHub.production?
81. How GitHub uses linters @joelhawksley class DoNotBranchOnGitHub MSG = "Don't branch on GitHub, code paths should not differ between test and production.”.freeze def_node_search :github_env, <<~PATTERN (send (const nil? :GitHub) ${:test? :production?}) PATTERN def on_if(node) if github_env(node.condition) add_offense(node.condition) end end end
82. How GitHub uses linters @joelhawksley $ require 'parser/current' $ p Parser::CurrentRuby.parse("GitHub.production?") $ => s(:send, s(:const, nil, :GitHub), :production?)
83. How GitHub uses linters @joelhawksley class DoNotBranchOnGitHub MSG = "Don't branch on GitHub, code paths should not differ between test and production.”.freeze def_node_search :github_env, <<~PATTERN (send (const nil? :GitHub) ${:test? :production?}) PATTERN def on_if(node) if github_env(node.condition) add_offense(node.condition) end end end
84. How GitHub uses linters @joelhawksley class DoNotBranchOnGitHub MSG = "Don't branch on GitHub, code paths should not differ between test and production.”.freeze def_node_search :github_env, <<~PATTERN (send (const nil? :GitHub) ${:test? :production?}) PATTERN def on_if(node) if github_env(node.condition) add_offense(node.condition) end end end
85. How GitHub uses linters @joelhawksley class DoNotBranchOnGitHub MSG = "Don't branch on GitHub, code paths should not differ between test and production.”.freeze def_node_search :github_env, <<~PATTERN (send (const nil? :GitHub) ${:test? :production?}) PATTERN def on_if(node) binding.irb if github_env(node.condition) add_offense(node.condition) end end end
86. How GitHub uses linters @joelhawksley if GitHub.test? do_the_fake_thing else do_the_real_thing end
87. How GitHub uses linters @joelhawksley $ node => s(:if, s(:send, s(:const, nil, :GitHub), :test?), s(:send, nil, :do_the_fake_thing), s(:send, nil, :do_the_real_thing)) $ node.condition => s(:send, s(:const, nil, :GitHub), :test?) $ node.condition.receiver.short_name => :GitHub $ node.condition.method_name => :test?
88. How GitHub uses linters @joelhawksley $ node => s(:if, s(:send, s(:const, nil, :GitHub), :test?), s(:send, nil, :do_the_fake_thing), s(:send, nil, :do_the_real_thing)) $ node.condition => s(:send, s(:const, nil, :GitHub), :test?) $ node.condition.receiver.short_name => :GitHub $ node.condition.method_name => :test?
89. How GitHub uses linters @joelhawksley $ node => s(:if, s(:send, s(:const, nil, :GitHub), :test?), s(:send, nil, :do_the_fake_thing), s(:send, nil, :do_the_real_thing)) $ node.condition => s(:send, s(:const, nil, :GitHub), :test?) $ node.condition.receiver.short_name => :GitHub $ node.condition.method_name => :test?
90. How GitHub uses linters @joelhawksley $ node => s(:if, s(:send, s(:const, nil, :GitHub), :test?), s(:send, nil, :do_the_fake_thing), s(:send, nil, :do_the_real_thing)) $ node.condition => s(:send, s(:const, nil, :GitHub), :test?) $ node.condition.receiver.short_name => :GitHub $ node.condition.method_name => :test?
91. How GitHub uses linters @joelhawksley def on_if(node) if github_env(node.condition) add_offense(node.condition) end end
92. How GitHub uses linters @joelhawksley def on_if(node) return unless node.condition.receiver.short_name == :GitHub end
93. How GitHub uses linters @joelhawksley def on_if(node) return unless node.condition.receiver.short_name == :GitHub return unless( [:test?, :production?]. include?(node.condition.method_name) ) end
94. How GitHub uses linters @joelhawksley def on_if(node) return unless node.condition.receiver.short_name == :GitHub return unless( [:test?, :production?]. include?(node.condition.method_name) ) add_offense(node.condition) end
95. How GitHub uses linters @joelhawksley def on_if(node) return unless node.condition.receiver.short_name == :GitHub return unless( [:test?, :production?]. include?(node.condition.method_name) ) add_offense(node.condition) end
96. How GitHub uses linters @joelhawksley Specific Timely Actionable
97. How GitHub uses linters @joelhawksley Specific Timely Actionable
99. How GitHub uses linters @joelhawksley Specific Timely Actionable
100. How GitHub uses linters @joelhawksley ✨ Autocorrection
101. @kytrinyx Katrina Owen How GitHub uses linters @joelhawksley
102. How GitHub uses linters @joelhawksley # no assert_equal nil, value # yes! assert_nil value
103. How GitHub uses linters @joelhawksley def autocorrect(node) # => lambda(corrector#replace) end
104. How GitHub uses linters @joelhawksley assert_equal nil, value ✨✨✨✨✨✨✨✨ assert_nil value
105. How GitHub uses linters @joelhawksley # lib/parser/source/tree_rewriter.rb # Replaces the the source range `range` with `content`. # # @param [Range] range # @param [String] content def replace(range, content) combine(range, replacement: content) end
106. How GitHub uses linters @joelhawksley # range assert_equal nil, value # content assert_nil value
107. How GitHub uses linters @joelhawksley def autocorrect(node) binding.irb end
108. How GitHub uses linters @joelhawksley $ node $ => s(:send, nil, :assert_equal, s(:nil), s(:send, nil, :value)) $ node.arguments.last.source $ => "value" $ node.source_range $ => #<Parser::Source::Range (string) 0...23>
109. How GitHub uses linters @joelhawksley $ node $ => s(:send, nil, :assert_equal, s(:nil), s(:send, nil, :value)) $ node.arguments.last.source $ => "value" $ node.source_range $ => #<Parser::Source::Range (string) 0…23>
110. How GitHub uses linters @joelhawksley $ node $ => s(:send, nil, :assert_equal, s(:nil), s(:send, nil, :value)) $ node.arguments.last.source $ => "value" $ node.source_range $ => #<Parser::Source::Range (string) 0…23>
111. How GitHub uses linters @joelhawksley def autocorrect(node) lambda do |corrector| corrector.replace( node.source_range, # new_source ) end end
112. How GitHub uses linters @joelhawksley def autocorrect(node) lambda do |corrector| corrector.replace( node.source_range, # new_source ) end end
113. How GitHub uses linters @joelhawksley def autocorrect(node) lambda do |corrector| corrector.replace( node.source_range, # new_source ) end end
114. How GitHub uses linters @joelhawksley def autocorrect(node) lambda do |corrector| corrector.replace( node.source_range, # new_source ) end end
115. How GitHub uses linters @joelhawksley def autocorrect(node) lambda do |corrector| corrector.replace( node.source_range, "assert_nil #{node.arguments.last.source}” ) end end
116. How GitHub uses linters @joelhawksley Specific Timely Actionable
117. How GitHub uses linters @joelhawksley Abstract Syntax Trees
118. How GitHub uses linters @joelhawksley Conclusion
119. How GitHub uses linters @joelhawksley Consistent practices
120. How GitHub uses linters @joelhawksley Specific Timely Actionable
121. How GitHub uses linters @joelhawksley Specific Timely Actionable
122. How GitHub uses linters @joelhawksley Specific Timely Actionable
123. How GitHub uses linters @joelhawksley Elevate the conversation
124. How GitHub uses linters @joelhawksley Value
125. How GitHub uses linters @joelhawksley Why
126. How GitHub uses linters @joelhawksley The Big Picture
127. How GitHub uses linters @joelhawksley But at what cost?
128. How GitHub uses linters @joelhawksley To what end?
129. “ How GitHub uses linters @joelhawksley No code is better than no code
130. “ How GitHub uses linters @joelhawksley No linter is better than no linter
131. How GitHub uses linters @joelhawksley Safety
132. How GitHub uses linters @joelhawksley Ruby is Dynamic!
133. How GitHub uses linters @joelhawksley Statically Typed
134. How GitHub uses linters @joelhawksley Compiled
135. How GitHub uses linters @joelhawksley Static analysis
136. How GitHub uses linters @joelhawksley Correct by design
137. How GitHub uses linters @joelhawksley Thanks