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Hello!
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Божидар
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Bozhidar
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Божo
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Bozho
cool
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Bozo
not
cool
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Bozho is not a bozo!
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Bozho is not a bozo!
(at least he claims so)
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Bug
cool
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(The RuboCop Guy)
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Sofia, Bulgaria
Sofia, Bulgaria
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Grigor Dimitrov vs Kei Nishikori
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Lukanka
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Bulgarian Cheese
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Rakia
Connecting People
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Shopska Salad
(use only with Rakia)
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bbatsov
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Ruby & Rails
style guides
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First time in Japan!!!
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All
About
RuboCop
by Bozhidar Batsov
(a.k.a. bug)
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Writing Lint
for
Ruby
by Masataka Kuwabara
(a.k.a. Pocke)
http://rubykaigi.org/2017/presentations/p_ck_.html
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Improve Ruby
coding style
rules and Lint
by Koichi Ito
http://rubykaigi.org/2018/presentations/koic.html#jun01
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Something
About
RuboCop
by Bozhidar Batsov
(a.k.a. bug)
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RuboCop in a
Nutshell
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A Ruby static code analysis
tool aimed to enforce the
Ruby Community Style Guide
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In other words…
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It keeps your
codebase consistent
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It saves you time
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It advances the Ruby
language forward
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32,608,128
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Provides an efficient
way for codebases to be
updated
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Disclaimer
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Lint tools are not a
replacement for
common sense
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Why an entire talk about
a mere lint tool?
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Notable Japanese
Contributors
• Yuji Nakayama (@yujinakayama)
• Masataka Kuwabara (@pocke)
• Koichi Ito (@koic)
• Yukihiro "Matz" Matsumoto (@matz) ;-)
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https://github.com/rubocop-jp/issues
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https://github.com/fortissimo1997/ruby-style-guide
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314 open issues
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100 volunteers
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3.14 issues/person
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Coincidence?
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Or providence?
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A Brief History of Time
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A Brief History of
RuboCop
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2011
The Ruby Style Guide
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May, 2012
RuboCop 0.0.0
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May, 2012
RuboCop 0.0.0
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Static code analysis
with regular
expressions …
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Nov, 2012
Along Came Jonas
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Spring, 2013
Return of the Jedi
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Using a proper
parser!
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Struggles with Ripper
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Ripper supported
only MRI
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I wanted to build a
cross-platform tool
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Ripper had (has?)
almost no
documentation
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Ripper is tied to the
underlying Ruby
runtime
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…which means you can’t
parse code as Ruby 2.3
while running Ruby 2.5
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Ripper has a very hard
to work with AST
representation
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pry(main)> Ripper.sexp('alias :some :test')
=> [:program,
[[:alias,
[:symbol_literal, [:symbol, [:@ident, "some", [1, 7]]]],
[:symbol_literal, [:symbol, [:@ident, "test", [1, 13]]]]]]]
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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
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And many quirks…
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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"]]
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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, ")"]]
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Which no one really
considered
problematic…
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Parser: A New Hope
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parser is
cross-platform
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well documented
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supports multiple
parsing targets
(Ruby 1.9 - 2.5)
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easy to work with ast
format
https://github.com/whitequark/ast
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p Parser::CurrentRuby.parse("2 + 2")
# (send
# (int 2) :+
# (int 2))
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AST node source
location mappings
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p Parser::CurrentRuby.parse("2 + 2").loc
# #,
# @expression=#>
p Parser::CurrentRuby.parse("2 + 2").loc.selector.source
# "+"
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$ 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
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powerful code
rewriting capabilities
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Struggles with Parser
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Parser was brand
new
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Had no real users
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And had plenty of
bugs…
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Peter Zotov
(@whitequark)
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28th May, 2013
State of Unity
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RuboCop 0.8
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1st July, 2013
RuboCop 0.9
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Formatters
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Auto-correct
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Commissioner
(single parsing run triggers all cops)
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Results caching
(rubocop —-cache)
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Parallel Checks
(rubocop —-parallel)
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Pattern Matching
(regex-style matching for ast nodes)
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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)
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Style/ArrayJoin (now)
def_node_matcher :join_candidate?, '(send $array :* $str)'
def on_send(node)
join_candidate?(node) { add_offense(node, location: :selector) }
end
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RuboCop Today
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Started out with no
configuration at all…
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Today things are
infinitely configurable
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Metrics/LineLength:
Enabled: false
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Metrics/LineLength:
Max: 100
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Style/StringLiterals:
Enabled: false
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Style/StringLiterals:
EnforcedStyle: double_quotes
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You can set a target
Ruby/Rails version
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You can limit cops to
certain folders with
Exclude/Include directives
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You can have different
settings for the same cops
in different directories
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You can inherit
between configuration
files
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You can auto-generate
an initial configuration
for your project
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rubocop —-auto-gen-config
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And you can read
about all of this in
RuboCop’s manual…
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rubocop.readthedocs.io
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gry is a smarter
alternative to the
built-in command
https://github.com/pocke/gry
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RuboCop started as a
code style checker
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•Style
•Lint
•Layout
•Naming
•Security
•Performance
•Performance
•Rails
•Bundler
•Metric
•Gemspec
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RuboCop is a great
code formatter
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rubocop —-only Layout -a
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RuboCop does some
linting better than
ruby -w
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rubocop —-lint
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You can extend
RuboCop with your
own cops
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Granite
(business actions architecture for Rails applications)
https://toptal.github.io/granite/
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$ bundle exec rake new_cop[Department/Name]
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https://rubocop.readthedocs.io/
en/latest/development/
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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
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RuboCop has a rich
ecosystem of
extensions
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189!!!
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Notable Extensions
• rubocop-rspec
• guard-rubocop
• rubocop-sequel
• rubocop-cask
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Integration with code
quality services
•Code Climate
•HoundCI
•SideCI
•Codacy
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RuboCop has
integrations with
many editors and IDEs
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Emacs 26.1 is out
and it’s amazing!
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(spacemacs)
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The Road to
RuboCop 1.0
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#1 question I get
asked about RuboCop?
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When is RuboCop 1.0
coming?
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Remove Rails
(and maybe Performance)
cops from RuboCop’s core
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Provide a proper (and
stable) API for writing
RuboCop extensions
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Introducing the brand
new RuboCop HQ!
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https://github.com/bbatsov/rubocop
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https://github.com/rubocop-hq/rubocop
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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)
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Review the config of all
cops and come up with
the best defaults
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Ideally each default
should be backed by
solid data/rationale
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Adjust the list of
enabled by default cops
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Come up with a less painful
process for dealing with new
cops and configuration changes
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mry makes RuboCop
upgrades less painful
https://github.com/pocke/mry
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Agree on what’s going to
be constituting breaking
changes down the road
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Breaking changes
•Cop API changes
•Extension API changes
•Dropping support for Ruby versions
•Renaming/removing cops
•Renaming/changing/removing config values
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Cop status “New” in
minor releases
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Cop status gets changed
to Enabled/Disabled in
major releases
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Extra Cop metadata
•Version added
•Version default config changed
•Version deprecated
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eslint.org-grade
manual/website
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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
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That’s a lot of work!
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Apes Together Strong!
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Rubyists Together Strong!
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Felina
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Thanks!
twitter: @bbatsov
github: @bbatsov
http//batsov.com
http://emacsredux.com
RubyKaigi
Sendai,
Japan
31.05.2018