The Better RuboCop World to enjoy Ruby

by Yasuko Ohba

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The Better RuboCop World to enjoy Ruby 2022/9/10 Yasuko Ohba (@nay3) େ৔ೡࢠ

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Yasuko Ohba (@nay3) • Started programing in 1987 • Ruby (mostly Rails) user since 2006 • One of founders of Everyleaf Corporation (גࣜձࣾສ༿) in Japan • Recently came back to software development works • A RuboCop user

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We are hiring! https://www.everyleaf.com/ https://note.com/everyleaf/ ສ༿note

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In this talk I will talk about the problems that can arise in the development team using RuboCop and how to solve them RuboCopʢͷΑ͏ͳπʔϧʣΛ࢖͏͜ͱͰ  ։ൃνʔϜʹى͜ΓಘΔ໰୊ͱ  ͦͷղܾํ๏ʹ͍ͭͯ࿩͠·͢

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Thanks to RuboCop !! • I like and appreciate RuboCop  ɹRuboCopʹ͸େม͓ੈ࿩ʹͳ͓ͬͯΓײँ͍ͯ͠·͢ • I don’t intend to criticize RuboCop  ɹRuboCopΛdisΔҙਤ͸͋Γ·ͤΜ

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What I want to say Is there anything we can do to make RuboCop   (and similar tools) better and safer ?    ΑΓྑ҆͘શʹRuboCopΛར༻Ͱ͖ΔΑ͏ʹɺ  ͳʹ͔Ͱ͖Δ͜ͱ͸ͳ͍͔ʁ

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Let me ask you questions 1. Have you used RuboCop ?  ɹRuboCopΛ࢖ͬͨ͜ͱͷ͋Δํ✋ 2. Do you love RuboCop ?  ɹRuboCop͕େ޷͖ͳํ✋ 3. Have you felt uncomfortable with RuboCop ?  ɹRuboCopʹۤखײΛײͨ͜͡ͱͷ͋Δํ✋ 4. Have you written .rubocop.yml by yourself ?  ɹRuboCopͷઃఆϑΝΠϧʢ.rubocop.ymlʣΛ࡞ΓࠐΜͩ͜ͱͷ͋Δํ✋

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What is RuboCop ?

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• It checks your code and extract the problems  ɹίʔυΛνΣοΫ͠ɺ໰୊఺Λநग़ͯ͘͠Ε·͢ • Also has a function that fi xes problems automatically if possible  ɹࣗಈͰमਖ਼ͯ͘͠ΕΔػೳ΋͋Γ·͢ https://github.com/rubocop/rubocop

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Typical usage in teams • Prevent bad code from being committed by pre-commit hook  ɹpre-commitͰ૸Βͤͯɺ  ɹҧ൓͕͋Ε͹ίϛοτ͞Εͳ͍Α͏ʹ͢Δ • Prevent bad code from being merged by running RuboCop in CI  ɹCIͰ૸Βͤͯɺ  ɹҧ൓͕͋Ε͹Ϛʔδ͞Εͳ͍Α͏ʹ͢Δ

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In that case • RuboCop is just like a real cop  ɹܯ׭ͷΑ͏ʹ • It cracks down on codes that don't follow the rules  ɹϧʔϧʹԊ͍ͬͯͳ͍ίʔυΛݫ͘͠औΓక·Δ

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A By the way, all pictures in this slide are generated by Midjourny

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Good point VALUES = [ 'foo'.freeze, 'bar'.freeze ] Style/MutableConstant: Freeze mutable objects assigned to constants Layout/FirstArrayElementIndentation: Indent the right bracket the same as the start of the line where the left bracket is. VALUES = [ 'foo'.freeze, 'bar'.freeze ].freeze Very Useful !!

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It keeps code clean • Mostly you can automatically correct the code with a single command  ɹίϚϯυҰൃͰमਖ਼Ͱ͖Δ͜ͱ͕ଟ͍ • Teammates are freed from reviewing trivial mistakes  ɹࠣࡉͳελΠϧҧ൓ʹ͍ͭͯͷϨϏϡʔ͔Βͷղ์ • Only clean code goes into the main branch  ɹ͖Ε͍ͳίʔυ͚͕ͩmainϒϥϯνʹೖΔ҆৺ײ

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A happy end?

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There is potentially a big risk જࡏతʹ େ͖ͳϦεΫ͕͋Δ

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Sometimes the rules don't fi t the situation ϧʔϧ͸ ঢ়گʹ߹Θͳ͍͜ͱ΋͋Δ

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Examples (In my opinion)

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Example 1 class UsersController < ApplicationController def show end Style/EmptyMethod: Put empty method de fi nitions on a single line. • It's more convenient not to do so in this case  ɹैΘͳ͍΄͏͕͜ͷ৔߹͸ศར def show; end def show # just render it end

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Example 2 • Renaming makes it ambiguas in this case  ɹ໊લΛม͑Δͱ͔͑ͬͯᐆດʹͳΔ class ParentModel < ApplicationRecord def has_child? … Naming/PredicateName: Rename has_child? to child? def child?

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I can introduce a lot, but that is not the purpose, so not here ͨ͘͞Μ঺հͰ͖ΔΜ͚ͩͲ ͦΕ͕໨తͰ͸ͳ͍ͷͰׂѪ

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The rules are not "wrong" ϧʔϧ͕ʮؒҧ͍ͬͯΔʯ Θ͚Ͱ͸ͳ͍

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It's just that sometimes it doesn't fi t the situation ঢ়گʹ߹Θͳ͍͜ͱ͕͋Δͱ͍͏͚ͩ

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Let’s imagine a development team using RuboCop RuboCopΛ࢖͍ͬͯΔ։ൃνʔϜΛ ࢥ͍ු͔΂͍ͯͩ͘͞

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Let’s imagine how a junior engineer behaves when RuboCop detects a violation RuboCopͰҧ൓͕ݕग़͞ΕͨΒɺ δϡχΞΤϯδχΞ͸Ͳ͏͢Δ͔ʁ

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Most junior engineers try to follow the rules (Perhaps, particularly in Japan) େଟ਺ͷδϡχΞΤϯδχΞ͸ ϧʔϧʹै͓͏ͱ͢Δ (΋͔ͨ͠͠Βɺಛʹ೔ຊͰ͸…)

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This simple act to follow the rules can lead to tragic waste ϧʔϧʹै͓͏ͱ͢Δ͜ͱ͕ ൵ܶతͳແବʹͭͳ͕ΔڪΕ͕͋Δ

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Common tragedies for beginners ॳ৺ऀ͋Δ͋Δͷ൵ܶ

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8IZJTUIJTNFUIPE EJWJEFEMJLFUIJT *U`TSFBMMZIBSEUPSFBEGPSNF ͜ͷϝιουɺͲ͏ͯ͜͠͏͍͏;͏ʹ෼͚ͨͷʁ ͍͢͝ಡΈͮΒ͍Μ͚ͩͲ΋ʁ 3VCP$PQTDPMEFENF TP*EJWJEFEUIFNFUIPETPUIBU UIFZDPVMEQBTT 3VCP$PQʹౖΒΕͨͷͰ ௨ΔΑ͏ʹ෼͚·ͨ͠ʂ

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%JEOUZPVEPXIBU *BEWJTFEZPVUPEP ͋Εɺॿݴͨ͠Α͏ʹ΍Βͳ͔ͬͨͷʁ 3VCP$PQEJEOU BMMPXUIFN BOEXIJMF*XBTEPJOH WBSJPVTUIJOHT *QBTTFEXJUIUIJT 3VCP$PQͰϋϚͬͯ͠·ͬͯɺ͍Ζ͍Ζ΍ͬͯ Δ͏ͪʹɺ͜ΕͰ௨ͬͨͷͰ

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😫

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Beginners in the development team are forced to write code under the rules that they cannot judge for themselves ։ൃνʔϜ಺ͷॳ৺ऀ͸ɺ ࣗ෼ͰΑ͋͠͠Λ൑அͰ͖ͳ͍ϧʔϧʹ ੍໿͞Εͳ͕ΒίʔυΛॻ͘͜ͱʹͳΔ

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Ultimately, for beginners under RuboCop, RuboCop's allowed writing style == Ruby ۃ࿦͢ΔͱɺRuboCopΛ࢖͍ͬͯΔ νʔϜ಺ͷॳ৺ऀʹͱͬͯ͸ɺ RuboCopͰڐ͞Εͨॻ͖ํ == Ruby

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The Ruby language gives programmers a lot of freedom, but that freedom doesn't always reach beginners when using Ruby via RuboCop Rubyͷ༩͑ͯ͘ΕΔେ͖ͳࣗ༝͸ RuboCopӽ͠ʹRubyΛ࢖͏ͱ͖ ඞͣ͠΋ॳ৺ऀʹ͸ಧ͔ͳ͍

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“You can quickly write whatever you want with Ruby” ʮRubyΛ࢖͑͹ԿͰ΋ ࢥ͍௨Γʹαοͱॻ͚Δʯ

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I think we should question “Is it still true for beginners under RuboCop?” ʮRuboCopΛ࢖ͬͯRubyΛॻ͍͍ͯΔॳ৺ऀ ʹ΋ͦ͏ࢥͬͯ΋Β͑Δ͔Ͳ͏͔ʯ ͱ͍͏໰͍͔͚Λͨ͠΄͏͕͍͍ͷͰ͸ͳ͍͔

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Under RuboCop, unskilled people might be trapped while skilled people are enjoying Ruby freely εΩϧͷ͋Δਓ͸ RuboCopΛ࢖͍ͬͯͯ΋ RubyΛࣗ༝ʹָ͠ΊΔ͕ɺ εΩϧͷͳ͍ਓ͸RuboCopʹڧ੍͘໿͞ΕΔ

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Even for more skilled engineers, there are some concerns ΋ͬͱεΩϧ͕͋Δ૚ʹͱͬͯ΋ɺ ͍͔ͭ͘ͷݒ೦͕͋Δ

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It's annoying to have a rule that doesn't fi t your situation and get stuck frequently ঢ়گʹ߹Θͳ͍ϧʔϧʹ සൟʹҾ͔͔ͬΔͷ͸൥Θ͍͠

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It slows down development ։ൃ଎౓Λ௿Լͤ͞Δ

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Even after deciding that the rules don't fi t the situation, something needs to be done ϧʔϧ͕ঢ়گʹ߹Θͳ͍ͱ ൑அͰ͖ͨ৔߹Ͱ΋ɺ ͳʹ͔ͷରॲ͕ඞཁʹͳΔ

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Strategies 1. Change the rule for the project  ɹϓϩδΣΫτશମͷϧʔϧΛม͑Δ 2. Change the rule in that code  ɹͦͷίʔυͰ͸ϧʔϧΛม͑Δ 3. Just follow the rule  ɹͱΓ·ɺϧʔϧʹै͓ͬͯ͘

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Few engineers can take Strategy 1 ઓུ1ΛͱΕΔΤϯδχΞ͸ গ਺ʹײ͡ΒΕΔ 1. Change the rule for the project   ɹϓϩδΣΫτશମͷϧʔϧΛม͑Δ

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Dif fi culty of Strategy 1 • “I can't tell if that's the case in other situations as well.”  ɹʮ΄͔ͷέʔεͰ΋ঢ়گʹ߹Θͳ͍͔·Ͱ͸  ɹ൑அͰ͖ͳ͍ʯ • “It's hard to convince the whole team”  ɹʮνʔϜશһΛઆಘ͢Δͷ͸େมͦ͏ͩʯ 1. Change the rule for the project   ɹϓϩδΣΫτશମͷϧʔϧΛม͑Δ

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Taking easier strategies • This may not solve the problem conclusively  ɹ໰୊ͷ࠷ऴղܾʹͭͳ͕Βͣɺ  ɹ·ͨ͜ͷίετΛ෷͏ඞཁ͕ൃੜ͢Δ͔΋͠Εͳ͍ 2. Change the rule in that code  ɹͦͷίʔυͰ͸ϧʔϧΛม͑Δ 3. Just follow the rule  ɹͱΓ·ɺϧʔϧʹै͓ͬͯ͘

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In short "Rules that do not fi t the situation” create disadvantages ʮঢ়گʹ߹Θͳ͍ϧʔϧʯ͸ σϝϦοτΛੜΈग़͢

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Disadvantages • Decrease in development speed and productivity  ɹ։ൃ଎౓ɾੜ࢈ੑͷ௿Լ • Code might get worse to avoid violation  ɹRuboCopͷҧ൓Λආ͚ΔͨΊʹ  ɹίʔυ͕վѱ͞ΕΔϦεΫ

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Then what should we do? Ͱ͸Ͳ͏͢Δ͔ʁ

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Why don't you just set it up to fi t the situation? ঢ়گʹ߹͏Α͏ʹઃఆͨ͠Β ͍͍Μ͡ΌΜʁ

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RuboCop is fl exible (1) All rules can be disabled or customized from the default ͢΂ͯͷϧʔϧ͸ɺແޮʹͨ͠ΓɺσϑΥϧτͱ͸ҟͳΔ ํ਑ʹมߋ͢Δ͜ͱ͕Ͱ͖·͢

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RuboCop is fl exible (2) • You can ignore certain rules in a certain code  ಛఆͷίʔυͰಛఆͷϧʔϧΛແࢹ͢Δ͜ͱΛ  એݴͰ͖·͢

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RuboCop’s Philosophy “Whatever style preferences you have RuboCop is there for you. That's our promises and our guarantee.” https://docs.rubocop.org/rubocop/index.html#philosophy

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"Style Guide" • Ruby is a dynamic language  Ruby͸ಈతͳݴޠ • The good thing about Ruby is that you can write in the best way for your situation  ঢ়گʹ͋Θͤͯ࠷దͳॻ͖ํ͕Ͱ͖Δͷ͕Rubyͷ͍͍ͱ͜Ζ • In my opinion, the style guide in “Ruby Way” should be dynamic  RubyͬΆ͍ελΠϧΨΠυ͸ɺಈతͳͷͰ͸ͳ͍͔ʁ

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Well, you have the right not to use RuboCop I want to use RuboCop because it is useful, and it is already kind of standard  RuboCop͸ศརͳͷͰ࢖͍͍ͨ͠ɺ΋͸΍ඪ४త

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We need to harmonize good old Ruby and RuboCop ݹ͖Α͖RubyͱRuboCopͷ ௐ࿨ΛਤΔඞཁ͕͋Δ

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Point is • The need to use RuboCop is growing  ɹRuboCopΛ࢖͏ඞཁੑ͸ڧ͘ͳ͍ͬͯΔ • My concern is not about “(static) style guide preferences"  ʮͲͷ(੩తͳ) Style GuideΛ޷Ή͔ʯͰ͸ࡁ·ͳ͍࿩ͩͱࢥ͍ͬͯΔ • People may be forced to follow rules that do not fi t their situation  ɹঢ়گʹ߹Θͳ͍ϧʔϧΛڧ੍͞ΕΔϦεΫ͕͋Δ • Con fi guration fl exibility is not enough to avoid the risk  ɹઃఆͷॊೈ͚ͩ͞Ͱ͸ͦͷϦεΫΛճආͰ͖ͳ͍

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Con fi guration fl exibility is not enough to avoid the risk ઃఆͷॊೈ͚ͩ͞Ͱ͸ͦͷϦεΫΛճආͰ͖ͳ͍

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Why not enough ?

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Technical ability

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You need to judge the validity of the rule in order to set up ͏·͘ઃఆ͢ΔͨΊʹ͸ ϧʔϧͷଥ౰ੑΛ൑அͰ͖Δඞཁ͕͋Δ

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You need to think about whether problems will occur in all the code written in the future, not on the correctness at fi rst glance Ұݟͯ͠ͷਖ਼͠͞Ͱ͸ͳ͘ɺ  ະདྷʹॻ͔ΕΔίʔυ΋ؚΊͯ  ໰୊͕ى͖ͳ͍͔ߟ͑Δඞཁ͕͋Δ

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You need technical ability and experience to judge the validity looking to the future কདྷΛݟ௨ͯ͠ ͋Δϧʔϧ͕Ͳͷ͘Β͍ద੾͔Λ ൑அ͢Δʹ͸ٕज़ྗͱܦݧ͕ඞཁ

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Even the RuboCop team would not be able to foresee the future needs of every project in the world RuboCopνʔϜ΋ ͋ΒΏΔνʔϜͷະདྷͷχʔζΛ ༧૝͸Ͱ͖ͳ͍

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So what do we do? Ͱ͸ɺͲ͏͢Δʁ

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The surest way to avoid such disadvantages is to con fi gure the rules well for your team by yourself ໰୊Λ๷͙΋ͬͱ΋࣮֬ͳํ๏͸ɺ ࣗ෼ͨͪͷͨΊͷϧʔϧΛ ࣗ෼ࣗ਎Ͱ͏·͘ઃఆ͢Δ͜ͱ

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In my case • I’ve created a rule template of the baseline for our company  ɹࣗࣾ޲͚ͷϕʔεϥΠϯͷϧʔϧͷ਽ܗΛ࡞ͬͨ • WIP

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Disadvantages are gone !! ܶతϏϑΥʔΞϑλʔ !! ֨ஈʹ࢖͍΍͘͢ͳͬͨ

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I would like to introduce the details of that work, but I don't have time today ϧʔϧͮ͘Γͷৄࡉʹ͍ͭͯ΋͓࿩͍ͨ͠ Ͱ͕͢ࠓ೔͸͕࣌ؒͳͦ͞͏

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Just a bit ͪΐͬͱ͚ͩ

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Main evaluation viewpoints ओͳධՁ؍఺ 1. Risk that code will get worse  ɹίʔυ͕վѱ͞ΕΔϦεΫ 2. Avoid opposite values  ɹਅٯͷՁ஋؍ 3. Protect freedom of expression  ɹදݱͷࣗ༝ΛकΔ 4. Don't discourage DSL  ɹDSLԽʹྫྷਫΛ͔͚ͳ͍ I will write the rest part in our ‘ສ༿note' ଓ͖͸ສ༿noteʹͰ΋ ॻ͍͍͖͍ͯͨͱࢥ͍·͢

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You can get our settings here;  https://github.com/everyleaf/el-training/tree/master/rubocop    ɹઃఆྫ͸ɺສ༿ͷ  ɹ৽ೖࣾһڭҭ༻ΧϦΩϡϥϜ͔ΒऔಘͰ͖·͢

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A Happy End ?

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It’s too hard !! • Imagine if there is a right reason to want to break the rule  ɹϧʔϧʹҧ൓͍ͨ͠ਖ਼౰ͳཧ༝Λ૝૾ • Consider the frequency of that cases  ɹҧ൓ͨ͘͠ͳΔέʔεͷස౓Λݕ౼ • Compare the advantages and disadvantages of adopting the rule  ɹϧʔϧΛద༻͢ΔϝϦοτͱσϝϦοτΛൺֱ • Continue to make judgments as new rules coming  ɹࠓޙ΋৽͍͠ϧʔϧ͕௥Ճ͞ΕΔͨͼʹܧଓతʹબผ࡞ۀ

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Not everyone can do this ΈΜͳ͕͜ΕΛ ΍Δͷ͸ແཧͩͱࢥ͏

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I really didn't want to do this ࢲ΋ຊ౰͸΍Γͨ͘ͳ͔ͬͨ ΍Βͳ͍ͰࡁΉ΄͏͕خ͍͠

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Some teams don't have skilled people ख़࿅ऀͷ͍ͳ͍νʔϜͩͬͯ͋Δ

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Where is this suffering coming from? ͜ͷۤ͠Έ͸ Ͳ͔͜Βདྷ͍ͯΔʁ

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RuboCop seems to take the view that there is a concept of 'style' on the surface of the code, and it can be statically determined to be correct or not RuboCop͸ɺίʔυͷද૚ʹελΠϧͱ͍͏֓೦͕ ͋ΓɺԿ͕ྑ͍ελΠϧ͔͸ৗʹ੩తʹܾΊΒΕΔͱ ͍͏෺ͷݟํΛ͍ͯ͠ΔΑ͏ʹײ͡Δ

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Part of this view fi ts to Ruby, and part does not ͜ͷ෺ͷݟํ͸ Rubyʹ౰ͯ͸·Δ෦෼ͱ ౰ͯ͸·Βͳ͍෦෼͕͋Δ

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For example, how about DSLs ?

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Poem The code expression that RuboCop treats as style is sometimes not the style but the heart RuboCop͕ελΠϧͱͯ͠ ѻ͍ͬͯΔίʔυ্ͷදݱ͸ɺ ࣌ʹɺελΠϧͰ͸ͳ͘৺Ͱ͋Δ

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Values that RuboCop expects to be static can be changed fl exibly depending on the situation RuboCop͕੩తʹܾΊΒΕΔ ૝ఆͱ͍ͯ͠ΔʮՁ஋؍ʯ͸ɺ ঢ়گ࣍ୈͰॊೈʹมΘΔ΋ͷ

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Each style (rule) has a different ‘ fi rmness’ ϧʔϧʢελΠϧʣͷ’ݻ͞’ͷ౓߹͍͸ͦΕͧΕҟͳΔ

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3VMF" 3VMF# 3VMF$ 3VMF$ 3VMF# "MMQPTTJCMFTJUVBUJPOT ͋Γ͑Δ͢΂ͯͷঢ়گ 3VMF" 4JUVBUJPO$PWFSBHFT %BNBHFDBVTFECZ SVMFTUIBUEPOPU fi UUIFTJUVBUJPO ‘Firm’

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We have a dilemma here δϨϯϚ͕͋Δ

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The more willingly you detect points that could be improved, the more "rules that don't fi t the situation" you get վળͰ͖Δ͔΋͠Εͳ͍ϙΠϯτΛ ҙཉతʹݕग़͢Δ΄Ͳ ʮঢ়گʹ߹Θͳ͍ϧʔϧʯ͕ଟ͘ͳΔ

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The solution of this dilemma is left to your .rubocop.yml ͜ͷδϨϯϚͷղܾ͕ ͦΕͧΕͷ .rubocop.yml ʹ ҕͶΒΕ͍ͯΔ

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Powerful, but painful

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Painful things 1. Hardness to tune .rubocop.yml  ɹઃఆ͕େม 2. Suffering from the "rules that do not match the situation" without tuning  ɹઃఆ͠ͳ͚Ε͹ʮঢ়گʹ߹Θͳ͍ϧʔϧʯ໰୊͕ൃੜ 3. Reducing damages also reduces the opportunities  ɹڧ੍ʹΑΔμϝʔδΛ࠷খԽ͢Δͱɺ  ɹίʔυվળͷػձ΋ݮͬͯ͠·͏

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Is there any way to solve this?

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My proposal

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Let's divide the usage of RuboCop into two levels   RuboCopͷ࢖͍ํΛ ̎ͭͷܥ౷ʹ෼͚ͨΒྑͦ͞͏ʁ 1. Enforcement Levelɹڧ੍Ϩϕϧ 2. Information LevelɹࢀߟϨϕϧ

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2 con fi g fi les • .rubocop-e.yml - for Enforcement Level • .rubocop-i.yml - for Information Level    ※names are examples  ɹɹ໊લ͸ҰྫͰ͢

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.rubocop-e.yml Include rules that can be enforced in almost all situations    ɹڧ੍ͯ͠΋ɺ΄΅100%ͷঢ়گͰ  ɹ໰୊͕ͳ͍Α͏ͳϧʔϧΛೖΕΔ

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.rubocop-i.yml Include ideal rules    ɹͳΔ΂͘ଟ͘ͷվળϙΠϯτʹؾ͚ͮΔΑ͏ʹ  ɹཧ૝తͳϧʔϧΛೖΕΔ

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How to use Enforcement Level ڧ੍Ϩϕϧͷ࢖͍ํ Guard your code base by using pre-commit hook or CI  ɹ  ɹݱঢ়Ͳ͓ΓɺCIͳͲͰΨʔυ͢Δ

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How to use Information Level ࢀߟϨϕϧͷ࢖͍ํ • Regularly run in CI etc  ɹCIͳͲͰఆظ࣮ߦ • Informative level violations should be labeled as "informative" not “violations"  ɹࢀߟϨϕϧͰͷҧ൓͸  ɹʮҧ൓ʯͰ͸ͳ͘ʮࢀߟ৘ใʯͱͯ͠දࣔ͢Δ

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Otherwise we'll fall into the trap of "rules that don't fi t the situation" ʮҧ൓ʯͱͯ͠ݟ͑Δͱ ʮঢ়گʹ߹Θͳ͍ϧʔϧʯͷ᠘ʹ ϋϚͬͯ͠·͏

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How does this solve the problem? ͜Ε͕໰୊ΛͲ͏ղܾ͢Δͷ͔ʁ

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• The reason why it is dif fi cult to use other people's settings is that there are a wide range of options for how to compromise ideals and reality.  ɹଞਓͷઃఆͷ׆༻͕೉͍͠ҰҼ͸ɺ  ɹཧ૝ͱݱ࣮ͷંΓ߹͍ͷ෇͚ํ͕෯޿͍͔Β • Splitting the levels into lower and upper limits increases the chances of a match  ɹൣғͷ্ݶɾԼݶΛ෼͚Ε͹ɺҰக͠΍͘͢ͳΔ • Easier and safer to borrow  ɹ҆৺ͯ͠ഈआͰ͖Δ 1.Hardness to tune .rubocop.yml  ɹઃఆ͕େม

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Maybe we can create typical enforcing level setting examples  for each use case  (For Rails, for Matz, etc) ༻్ผͷڧ੍Ϩϕϧͷ ઃఆྫΛ࡞ΕΔͱࢥ͏  ʢRails޲͚ͱ͔ɺMatz޲͚ͱ͔ʣ

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If a good "enforcement level setting" can be obtained at a low cost, it will be solved    ྑ͍ʮڧ੍Ϩϕϧͷઃఆʯ͕௿ίετͰೖखͰ͖Ε͹ɺ  ղܾʂʂʂ 2. Suffering from the "rules that do not match the situation" without tuning  ɹઃఆ͠ͳ͚Ε͹ʮঢ়گʹ߹Θͳ͍ϧʔϧʯ໰୊͕ൃੜ

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It makes you feel much less guilty to think “the rule is for reference” than “the violation won't have to be fi xed” ʮͦͷϧʔϧ͸ࢀߟ༻ʹ͠Α͏ʯͷ΄͏͕  ʮҧ൓Λ௚͞ͳ͍͍ͯ͘͜ͱʹ͠Α͏ʯΑΓ  ͣͬͱࡑѱײ͕গͳ͍

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This leads to creating a culture   that can counteract   the "rules that don't fi t the situation" trap ʮঢ়گʹ߹Θͳ͍ϧʔϧʯͷ᠘ʹ ର߅Ͱ͖ΔจԽΛ࡞Δ͜ͱ͕Ͱ͖Δ

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We can have a nice information level  code improvement suggestion system ࢀߟϨϕϧͷνΣοΫʹجͮ͘  ૉఢͳίʔυվળఏҊγεςϜΛ  ར༻Ͱ͖Δͱ͍͍ͳ…ʢເʣ 3. Reducing damages also reduces the opportunities  ɹڧ੍ʹΑΔμϝʔδΛ࠷খԽ͢Δͱɺ  ɹίʔυվળͷػձ΋ݮͬͯ͠·͏

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There is a gradation in the validity ( fi rmness) of rules ϧʔϧͷଥ౰ੑʢݻ͞ʣʹ͸άϥσʔγϣϯ͕͋Δ Fits 100% Fits 80%  ɹex. Not suitable if expressibility is   more important than consistency for you Fits 90%  ɹex. Not suitable for DSLs Unstable Firm rules

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Let's stop dividing the indivisible ! ෼͚ΒΕͳ͍΋ͷΛ෼͚ΔͷΛ΍ΊΑ͏ (00% #"% Our only one standard

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Make it easier to handle areas that cannot be determined by 0/1 0/1Ͱ൑ఆͰ͖ͳ͍ྖҬΛѻ͍΍͘͢ (00% #"% .":#&(00% )VNBOTDBOBMTPSFWJFXBOEKVEHF Enforcement Information

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Epilogue

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One Saturday morning,  I was working on .rubocop.yml for our company ͋Δ౔༵೔ͷேɺ  ձࣾͷRuboCopઃఆͮ͘ΓΛ  ͍ͯ͠·ͨ͠

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I've been thinking about the things I talked about today,   and I thought about it again that morning    ࠓ೔࿩ͨ͜͠ͱ͸ Ҏલ͔ΒԿճ͔ࢥ͍ͬͯ·͕ͨ͠ɺ ͜ͷ೔ͷே΋ߟ͑·ͨ͠

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Is there anything I can doʁ

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Then I realized that day was the CFP deadline for ͪΐ͏Ͳͦͷ೔͕ɺCFPకΊ੾Γͷ೔ͩͬͨ

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I felt like I could talk, that’s why I am here

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I would be happy if it helps to realize a better RuboCop World ࠓ೔ͷτʔΫ͕ ΑΓྑ͍ RuboCop World ͷ ࣮ݱʹ໾ཱͬͨΒخ͍͠Ͱ͢

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Thank you very much !! And, special thanks to Koichiro Ohba (@koichiroo)