All About RuboCop (RubyKaigi 2018)

Transcript

1. 1.

   Hello!

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   Божидар

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   None
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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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    None
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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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    None
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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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    None
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    Notable Japanese Contributors • Yuji Nakayama (@yujinakayama) • Masataka Kuwabara

    (@pocke) • Koichi Ito (@koic) • Yukihiro "Matz" Matsumoto (@matz) ;-)
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    None
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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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    None
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    May, 2012 RuboCop 0.0.0

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    May, 2012 RuboCop 0.0.0

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    None
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    Static code analysis with regular expressions …

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    None
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    Nov, 2012 Along Came Jonas

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    None
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    None
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    Spring, 2013 Return of the Jedi

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    Using a proper parser!

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    None
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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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    None
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    None
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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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    None
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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 # #<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 # "+"
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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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     None
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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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     None
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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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     None
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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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     None
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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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     None
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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