The Better RuboCop World to enjoy Ruby

The slide of my talk in RubyKaigi 2022.

https://rubykaigi.org/2022/presentations/nay3.html#day3

Transcript

1. The Better RuboCop World to enjoy Ruby 2022/9/10 Yasuko Ohba (@nay3) େ৔ೡࢠ
2. 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
3. We are hiring! https://www.everyleaf.com/ https://note.com/everyleaf/ ສ༿note
4. 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࿩͠·͢
5. Thanks to RuboCop !! • I like and appreciate RuboCop
 ɹRuboCopʹ͸େม͓ੈ࿩ʹͳ͓ͬͯΓײँ͍ͯ͠·͢ • I don’t intend to criticize RuboCop
 ɹRuboCopΛdisΔҙਤ͸͋Γ·ͤΜ
6. What I want to say Is there anything we can do to make RuboCop 
 (and similar tools) better and safer ?
 
 ΑΓྑ҆͘શʹRuboCopΛར༻Ͱ͖ΔΑ͏ʹɺ
 ͳʹ͔Ͱ͖Δ͜ͱ͸ͳ͍͔ʁ
7. 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✋
8. What is RuboCop ?
9. • 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
10. 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
11. 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
12. A By the way, all pictures in this slide are generated by Midjourny
13. 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 !!
14. 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
16. A happy end?
17. There is potentially a big risk જࡏతʹ େ͖ͳϦεΫ͕͋Δ
18. Sometimes the rules don't fi t the situation ϧʔϧ͸ ঢ়گʹ߹Θͳ͍͜ͱ΋͋Δ
19. Examples (In my opinion)
20. 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
21. 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?
22. I can introduce a lot, but that is not the purpose, so not here ͨ͘͞Μ঺հͰ͖ΔΜ͚ͩͲ ͦΕ͕໨తͰ͸ͳ͍ͷͰׂѪ
23. The rules are not "wrong" ϧʔϧ͕ʮؒҧ͍ͬͯΔʯ Θ͚Ͱ͸ͳ͍
24. It's just that sometimes it doesn't fi t the situation ঢ়گʹ߹Θͳ͍͜ͱ͕͋Δͱ͍͏͚ͩ
25. Let’s imagine a development team using RuboCop RuboCopΛ࢖͍ͬͯΔ։ൃνʔϜΛ ࢥ͍ු͔΂͍ͯͩ͘͞
26. Let’s imagine how a junior engineer behaves when RuboCop detects a violation RuboCopͰҧ൓͕ݕग़͞ΕͨΒɺ δϡχΞΤϯδχΞ͸Ͳ͏͢Δ͔ʁ
27. Most junior engineers try to follow the rules (Perhaps, particularly in Japan) େଟ਺ͷδϡχΞΤϯδχΞ͸ ϧʔϧʹै͓͏ͱ͢Δ (΋͔ͨ͠͠Βɺಛʹ೔ຊͰ͸…)
28. This simple act to follow the rules can lead to tragic waste ϧʔϧʹै͓͏ͱ͢Δ͜ͱ͕ ൵ܶతͳແବʹͭͳ͕ΔڪΕ͕͋Δ
29. Common tragedies for beginners ॳ৺ऀ͋Δ͋Δͷ൵ܶ
30. 8IZ
    JT
    UIJT
    NFUIPE
    EJWJEFE
    MJLF
    UIJT
    *U`T
    SFBMMZ
    IBSE
    UP
    SFBE
    GPS
    NF
    ͜ͷϝιουɺͲ͏ͯ͜͠͏͍͏;͏ʹ෼͚ͨͷʁ
    ͍͢͝ಡΈͮΒ͍Μ͚ͩͲ΋ʁ 3VCP$PQ
    TDPMEFE
    NF
    TP
    *
    EJWJEFE
    UIF
    NFUIPE
    TP
    UIBU
    UIFZ
    DPVME
    QBTT
    3VCP$PQʹౖΒΕͨͷͰ
    ௨ΔΑ͏ʹ෼͚·ͨ͠ʂ
31. %JEOU
    ZPV
    EP
    XIBU
    
    *
    BEWJTFE
    ZPV
    UP
    EP
    ͋Εɺॿݴͨ͠Α͏ʹ΍Βͳ͔ͬͨͷʁ 3VCP$PQ
    EJEOU
    BMMPX
    UIFN
    BOE
    XIJMF
    *
    XBT
    EPJOH
    WBSJPVT
    UIJOHT
    *
    QBTTFE
    XJUI
    UIJT
    3VCP$PQͰϋϚͬͯ͠·ͬͯɺ͍Ζ͍Ζ΍ͬͯ Δ͏ͪʹɺ͜ΕͰ௨ͬͨͷͰ
32. 😫
33. 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
34. Ultimately, for beginners under RuboCop, RuboCop's allowed writing style == Ruby ۃ࿦͢ΔͱɺRuboCopΛ࢖͍ͬͯΔ νʔϜ಺ͷॳ৺ऀʹͱͬͯ͸ɺ RuboCopͰڐ͞Εͨॻ͖ํ == Ruby
35. 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
37. “You can quickly write whatever you want with Ruby” ʮRubyΛ࢖͑͹ԿͰ΋ ࢥ͍௨Γʹαοͱॻ͚Δʯ
38. I think we should question “Is it still true for beginners under RuboCop?” ʮRuboCopΛ࢖ͬͯRubyΛॻ͍͍ͯΔॳ৺ऀ ʹ΋ͦ͏ࢥͬͯ΋Β͑Δ͔Ͳ͏͔ʯ ͱ͍͏໰͍͔͚Λͨ͠΄͏͕͍͍ͷͰ͸ͳ͍͔
39. Under RuboCop, unskilled people might be trapped while skilled people are enjoying Ruby freely εΩϧͷ͋Δਓ͸ RuboCopΛ࢖͍ͬͯͯ΋ RubyΛࣗ༝ʹָ͠ΊΔ͕ɺ εΩϧͷͳ͍ਓ͸RuboCopʹڧ੍͘໿͞ΕΔ
41. Even for more skilled engineers, there are some concerns ΋ͬͱεΩϧ͕͋Δ૚ʹͱͬͯ΋ɺ ͍͔ͭ͘ͷݒ೦͕͋Δ
42. It's annoying to have a rule that doesn't fi t your situation and get stuck frequently ঢ়گʹ߹Θͳ͍ϧʔϧʹ සൟʹҾ͔͔ͬΔͷ͸൥Θ͍͠
43. It slows down development ։ൃ଎౓Λ௿Լͤ͞Δ
44. Even after deciding that the rules don't fi t the situation, something needs to be done ϧʔϧ͕ঢ়گʹ߹Θͳ͍ͱ ൑அͰ͖ͨ৔߹Ͱ΋ɺ ͳʹ͔ͷରॲ͕ඞཁʹͳΔ
45. 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
46. Few engineers can take Strategy 1 ઓུ1ΛͱΕΔΤϯδχΞ͸ গ਺ʹײ͡ΒΕΔ 1. Change the rule for the project 
 ɹϓϩδΣΫτશମͷϧʔϧΛม͑Δ
47. 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
48. 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
49. In short "Rules that do not fi t the situation” create disadvantages ʮঢ়گʹ߹Θͳ͍ϧʔϧʯ͸ σϝϦοτΛੜΈग़͢
50. Disadvantages • Decrease in development speed and productivity
 ɹ։ൃ଎౓ɾੜ࢈ੑͷ௿Լ • Code might get worse to avoid violation
 ɹRuboCopͷҧ൓Λආ͚ΔͨΊʹ
 ɹίʔυ͕վѱ͞ΕΔϦεΫ
51. Then what should we do? Ͱ͸Ͳ͏͢Δ͔ʁ
52. Why don't you just set it up to fi t the situation? ঢ়گʹ߹͏Α͏ʹઃఆͨ͠Β ͍͍Μ͡ΌΜʁ
53. RuboCop is fl exible (1) All rules can be disabled or customized from the default ͢΂ͯͷϧʔϧ͸ɺແޮʹͨ͠ΓɺσϑΥϧτͱ͸ҟͳΔ ํ਑ʹมߋ͢Δ͜ͱ͕Ͱ͖·͢
54. RuboCop is fl exible (2) • You can ignore certain rules in a certain code
 ಛఆͷίʔυͰಛఆͷϧʔϧΛແࢹ͢Δ͜ͱΛ
 એݴͰ͖·͢
55. 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
56. "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
57. 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
58. We need to harmonize good old Ruby and RuboCop ݹ͖Α͖RubyͱRuboCopͷ ௐ࿨ΛਤΔඞཁ͕͋Δ
59. 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
60. Con fi guration fl exibility is not enough to avoid the risk ઃఆͷॊೈ͚ͩ͞Ͱ͸ͦͷϦεΫΛճආͰ͖ͳ͍
61. Why not enough ?
62. Technical ability
63. You need to judge the validity of the rule in order to set up ͏·͘ઃఆ͢ΔͨΊʹ͸ ϧʔϧͷଥ౰ੑΛ൑அͰ͖Δඞཁ͕͋Δ
64. 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
65. You need technical ability and experience to judge the validity looking to the future কདྷΛݟ௨ͯ͠ ͋Δϧʔϧ͕Ͳͷ͘Β͍ద੾͔Λ ൑அ͢Δʹ͸ٕज़ྗͱܦݧ͕ඞཁ
66. Even the RuboCop team would not be able to foresee the future needs of every project in the world RuboCopνʔϜ΋ ͋ΒΏΔνʔϜͷະདྷͷχʔζΛ ༧૝͸Ͱ͖ͳ͍
67. So what do we do? Ͱ͸ɺͲ͏͢Δʁ
68. 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
69. In my case • I’ve created a rule template of the baseline for our company
 ɹࣗࣾ޲͚ͷϕʔεϥΠϯͷϧʔϧͷ਽ܗΛ࡞ͬͨ • WIP
70. Disadvantages are gone !! ܶతϏϑΥʔΞϑλʔ !! ֨ஈʹ࢖͍΍͘͢ͳͬͨ
71. I would like to introduce the details of that work, but I don't have time today ϧʔϧͮ͘Γͷৄࡉʹ͍ͭͯ΋͓࿩͍ͨ͠ Ͱ͕͢ࠓ೔͸͕࣌ؒͳͦ͞͏
72. Just a bit ͪΐͬͱ͚ͩ
73. 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·͢
74. You can get our settings here;
 https://github.com/everyleaf/el-training/tree/master/rubocop
 
 ɹઃఆྫ͸ɺສ༿ͷ
 ɹ৽ೖࣾһڭҭ༻ΧϦΩϡϥϜ͔ΒऔಘͰ͖·͢
75. A Happy End ?
76. 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
77. Not everyone can do this ΈΜͳ͕͜ΕΛ ΍Δͷ͸ແཧͩͱࢥ͏
78. I really didn't want to do this ࢲ΋ຊ౰͸΍Γͨ͘ͳ͔ͬͨ ΍Βͳ͍ͰࡁΉ΄͏͕خ͍͠
79. Some teams don't have skilled people ख़࿅ऀͷ͍ͳ͍νʔϜͩͬͯ͋Δ
80. Where is this suffering coming from? ͜ͷۤ͠Έ͸ Ͳ͔͜Βདྷ͍ͯΔʁ
81. 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
82. Part of this view fi ts to Ruby, and part does not ͜ͷ෺ͷݟํ͸ Rubyʹ౰ͯ͸·Δ෦෼ͱ ౰ͯ͸·Βͳ͍෦෼͕͋Δ
83. For example, how about DSLs ?
84. Poem The code expression that RuboCop treats as style is sometimes not the style but the heart RuboCop͕ελΠϧͱͯ͠ ѻ͍ͬͯΔίʔυ্ͷදݱ͸ɺ ࣌ʹɺελΠϧͰ͸ͳ͘৺Ͱ͋Δ
85. Values that RuboCop expects to be static can be changed fl exibly depending on the situation RuboCop͕੩తʹܾΊΒΕΔ ૝ఆͱ͍ͯ͠ΔʮՁ஋؍ʯ͸ɺ ঢ়گ࣍ୈͰॊೈʹมΘΔ΋ͷ
86. Each style (rule) has a different ‘ fi rmness’ ϧʔϧʢελΠϧʣͷ’ݻ͞’ͷ౓߹͍͸ͦΕͧΕҟͳΔ
87. 3VMF
    " 3VMF
    # 3VMF
    $ 3VMF
    $ 3VMF
    # "MM
    QPTTJCMF
    TJUVBUJPOT
    ͋Γ͑Δ͢΂ͯͷঢ়گ 3VMF
    " 4JUVBUJPO
    $PWFSBHFT %BNBHF
    DBVTFE
    CZ
    
    SVMFT
    UIBU
    EP
    OPU
    fi U
    UIF
    TJUVBUJPO
    ‘Firm’
88. We have a dilemma here δϨϯϚ͕͋Δ
89. 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
90. The solution of this dilemma is left to your .rubocop.yml ͜ͷδϨϯϚͷղܾ͕ ͦΕͧΕͷ .rubocop.yml ʹ ҕͶΒΕ͍ͯΔ
91. Powerful, but painful
92. 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·͏
93. Is there any way to solve this?
94. My proposal
95. Let's divide the usage of RuboCop into two levels 
 RuboCopͷ࢖͍ํΛ ̎ͭͷܥ౷ʹ෼͚ͨΒྑͦ͞͏ʁ 1. Enforcement Levelɹڧ੍Ϩϕϧ 2. Information LevelɹࢀߟϨϕϧ
96. 2 con fi g fi les • .rubocop-e.yml - for Enforcement Level • .rubocop-i.yml - for Information Level
 
 ※names are examples
 ɹɹ໊લ͸ҰྫͰ͢
97. .rubocop-e.yml Include rules that can be enforced in almost all situations
 
 ɹڧ੍ͯ͠΋ɺ΄΅100%ͷঢ়گͰ
 ɹ໰୊͕ͳ͍Α͏ͳϧʔϧΛೖΕΔ
98. .rubocop-i.yml Include ideal rules
 
 ɹͳΔ΂͘ଟ͘ͷվળϙΠϯτʹؾ͚ͮΔΑ͏ʹ
 ɹཧ૝తͳϧʔϧΛೖΕΔ
99. How to use Enforcement Level ڧ੍Ϩϕϧͷ࢖͍ํ Guard your code base by using pre-commit hook or CI
 ɹ
 ɹݱঢ়Ͳ͓ΓɺCIͳͲͰΨʔυ͢Δ
100. 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
101. Otherwise we'll fall into the trap of "rules that don't fi t the situation" ʮҧ൓ʯͱͯ͠ݟ͑Δͱ ʮঢ়گʹ߹Θͳ͍ϧʔϧʯͷ᠘ʹ ϋϚͬͯ͠·͏
102. How does this solve the problem? ͜Ε͕໰୊ΛͲ͏ղܾ͢Δͷ͔ʁ
103. 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·͏
104. • 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
105. Maybe we can create typical enforcing level setting examples
 for each use case
 (For Rails, for Matz, etc) ༻్ผͷڧ੍Ϩϕϧͷ ઃఆྫΛ࡞ΕΔͱࢥ͏
 ʢRails޲͚ͱ͔ɺMatz޲͚ͱ͔ʣ
106. 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
107. 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
108. This leads to creating a culture 
 that can counteract 
 the "rules that don't fi t the situation" trap ʮঢ়گʹ߹Θͳ͍ϧʔϧʯͷ᠘ʹ ର߅Ͱ͖ΔจԽΛ࡞Δ͜ͱ͕Ͱ͖Δ
109. 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·͏
110. 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
111. Let's stop dividing the indivisible ! ෼͚ΒΕͳ͍΋ͷΛ෼͚ΔͷΛ΍ΊΑ͏ (00% #"% Our only one standard
112. Make it easier to handle areas that cannot be determined by 0/1 0/1Ͱ൑ఆͰ͖ͳ͍ྖҬΛѻ͍΍͘͢ (00% #"% .":#&
     (00%
     )VNBOT
     DBO
     BMTP
     SFWJFX
     BOE
     KVEHF
      Enforcement Information
113. Epilogue
114. One Saturday morning,
 I was working on .rubocop.yml for our company ͋Δ౔༵೔ͷேɺ
 ձࣾͷRuboCopઃఆͮ͘ΓΛ
 ͍ͯ͠·ͨ͠
115. 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·ͨ͠
116. Is there anything I can doʁ
117. Then I realized that day was the CFP deadline for ͪΐ͏Ͳͦͷ೔͕ɺCFPకΊ੾Γͷ೔ͩͬͨ
118. I felt like I could talk, that’s why I am here
119. I would be happy if it helps to realize a better RuboCop World ࠓ೔ͷτʔΫ͕ ΑΓྑ͍ RuboCop World ͷ ࣮ݱʹ໾ཱͬͨΒخ͍͠Ͱ͢
120. Thank you very much !! And, special thanks to Koichiro Ohba (@koichiroo)