Evitando o Jenga® Driven Development @ Elixir Brasil 2018

Mover e remover código. Algo que fazemos praticamente todos os dias da nossa vida como programadores. O que podemos aprender a respeito de algo aparentemente tão mundano? Quais detalhes são frequentemente negligenciados e nos causam, silenciosamente, uma diversidade de problemas?

1. Jenga® Driven Development
2. Jenga? Jogo criado pela Leslie Scott e hoje distribuído pela Hasbro.
3. Jenga? O objetivo é mover peças de camadas intermediárias para o topo sem derrubar a torre.
4. Jenga? É um jogo divertido. Mas tenso, nervoso, dá ansiedade.
5. Jenga® Driven Development Evitando o
6. Olá João Britto Plataformatec britto noteu
7. ✈
8. ✈
9. Estamos contratando! http:/ /careers.plataformatec.com.br
15. Parte 1 Mo’ Code Mo’ Problems
16. Feature Creep
17. Feature Creep
18. –Grant Ammons “A product with lots of features does not make a great product. A great product is one that solves the customer’s problem in the simplest way possible. Great products deliver value, not features.”
19. maximizar valor " e minimizar custo #
20. –Sandi MacPherson “Whenever you build a new feature, you’re entering into a contract to keep that code up-to-date and compatible with all other features you’ll choose to add in the future.”
21. –Jeff Atwood “Every new line of code you willingly bring into the world is code that has to be debugged, code that has to be read and understood, code that has to be supported. Every time you write new code, you should do so reluctantly, under duress, because you completely exhausted all your other options.”
22. –Edsger W. Dijkstra “…if we wish to count lines of code, we should not regard them as ‘lines produced’ but as ‘lines spent’.”
23. –Mike Perham “No code runs faster than no code. No code has fewer bugs than no code. No code uses less memory than no code. No code is easier to understand than no code.”
24. No code is easier to delete than no code.
25. –Thomas Figg “The easiest code to delete is the code you avoided writing in the first place.”
26. Parte 2 Código Removível
27. Coisas mudam • Features nascem, crescem e eventualmente morrem. • Ainda faz sentido no contexto atual do meu produto? • Tem usuários suficientes para justificar sua existência? • Representa uma vulnerabilidade na stack? ou seja… • Está mais atrapalhando do que ajudando?
28. –Sandi Metz “The problem with poorly designed small applications is that if they are successful they grow up to be poorly designed big applications.”
29. Maslow
30. Maslow
31. Código pouco “removível” defmodule Animals do @animals ~w(cat dog fox)a def say(animal) when animal in @animals do apply(__MODULE__, animal, []) end def say(animal) do "What does the #{animal} say?" end def cat, do: "MEOW!" def dog, do: "WOOF!" def fox, do: "WHAT!" end Animals.say(:dog) # "WOOF!"
32. Código pouco “removível” defmodule Animals do @animals ~w(cat dog fox)a def say(animal) when animal in @animals do apply(__MODULE__, animal, []) end def say(animal) do "What does the #{animal} say?" end def cat, do: "MEOW!" def dog, do: "WOOF!" def fox, do: "WHAT!" end Animals.say(:dog) # "WOOF!"
33. Código pouco “removível” defmodule Animals do @animals ~w(cat dog fox)a def say(animal) when animal in @animals do apply(__MODULE__, animal, []) end def say(animal) do "What does the #{animal} say?" end def cat, do: "MEOW!" def fox, do: "WHAT!" end Animals.say(:dog) # ** (UndefinedFunctionError) function Animals.dog/0 # is undefined or private
34. Código pouco “removível” defmodule Animals do @animals ~w(cat dog fox)a def say(animal) when animal in @animals do apply(__MODULE__, animal, []) end def say(animal) do "What does the #{animal} say?" end def cat, do: "MEOW!" def fox, do: "WHAT!" end Animals.say(:dog) # ** (UndefinedFunctionError) function Animals.dog/0 # is undefined or private
35. Código pouco “removível” defmodule Animals do @animals ~w(cat fox)a def say(animal) when animal in @animals do apply(__MODULE__, animal, []) end def say(animal) do "What does the #{animal} say?" end def cat, do: "MEOW!" def fox, do: "WHAT!" end Animals.say(:dog) # "What does the dog say?"
36. Código mais “removível” defmodule Animals do @animals %{ cat: "MEOW!", dog: "WOOF!", fox: "WHAT!" } def say(animal) when is_atom(animal) do @animals[animal] || "What does the #{animal} say?" end end Animals.say(:dog) # => "WOOF!" Animals.say(:cow) # => "What does the cow say?"
37. Código mais “removível” defmodule Animals do @animals %{ cat: "MEOW!", dog: "WOOF!", fox: "WHAT!" } def say(animal) when is_atom(animal) do @animals[animal] || "What does the #{animal} say?" end end Animals.say(:dog) # => "WOOF!" Animals.say(:cow) # => "What does the cow say?"
38. Código mais “removível” defmodule Animals do @animals %{ cat: "MEOW!", dog: "WOOF!", fox: "WHAT!" } def say(animal) when is_atom(animal) do @animals[animal] || "What does the #{animal} say?" end end Animals.say(:dog) # => "WOOF!" Animals.say(:cow) # => "What does the cow say?"
39. –Sandi Metz “Dependencies are foreign invaders that represent vulnerabilities, and they should be concise, explicit, and isolated.”
40. –Thomas Figg “Good code isn’t about getting it right the first time. Good code is just legacy code that doesn’t get in the way.”
41. Parte 3 Removendo Código
42. Deveria ser tão simples quanto 1. Apagar o código 2. Arrumar os testes 3. Partir pro abraço $
43. Na prática…
44. Remoções Perigosas • Inexistente • Incorreta • Incompleta
45. Remoção Inexistente
46. Código intacto def do_stuff(things) do do_this(things) do_that(things) do_something_else() finish_doing_stuff() end
47. Código comentado def do_stuff(things) do do_this(things) # do_that(things) # do_something_else() finish_doing_stuff() end
48. Código condicionado def do_stuff(things) do do_this(things) if false do_that(things) do_something_else() end finish_doing_stuff() end
49. –Ned Batchelder “Most developers don't like getting rid of stuff. They want to keep chunks of code around in case they need them again. They worked hard to write that chunk of code. They debugged it, it works. They don't want to just throw it away.”
50. –Ned Batchelder “If you have a chunk of code you don't need any more, there's one big reason to delete it for real rather than leaving it in a disabled state: to reduce noise and uncertainty.”
51. Psicologia do controle de versão
52. Remoções Perigosas • Inexistente • Incorreta • Incompleta
53. Remoção Incorreta
55. Remoção Incorreta defmodule Animals do @animals ~w(cat dog fox)a def say(animal) when animal in @animals do apply(__MODULE__, animal, []) end def say(animal) do "What does the #{animal} say?" end def cat, do: "MEOW!" def fox, do: "WHAT!" end Animals.say(:dog) # ** (UndefinedFunctionError) function Animals.dog/0 # is undefined or private
56. Dependências ocultas %
57. Remoções Perigosas • Inexistente • Incorreta • Incompleta
58. Remoção Incompleta
59. Sacudir a árvore de dependências
61. Sacolejo Automático • Reduzir código entregue às máquinas • Passo de compilação/empacotamento • Código morto permanece no repositório
62. Sacolejo Manual • Reduzir código entregue às pessoas • Parte do fluxo de desenvolvimento • Código removido em definitivo
63. Removendo dependências <%= link gettext("Sacrifice %{creature} </3", creature: creature.nickname), to: creature_path(@conn, :delete, creature), method: :delete, data: [confirm: gettext("Are you sure?")], class: "btn btn-delete #{delete_creature_class(creature)}" %>
64. Removendo dependências <%= link gettext("Sacrifice %{creature} </3", creature: creature.nickname), to: creature_path(@conn, :delete, creature), method: :delete, data: [confirm: gettext("Are you sure?")], class: "btn btn-delete #{delete_creature_class(creature)}" %>
65. Removendo dependências <%= link gettext("Sacrifice %{creature} </3", creature: creature.nickname), to: creature_path(@conn, :delete, creature), method: :delete, data: [confirm: gettext("Are you sure?")], class: "btn btn-delete #{delete_creature_class(creature)}" %>
66. Removendo dependências <%= link gettext("Sacrifice %{creature} </3", creature: creature.nickname), to: creature_path(@conn, :delete, creature), method: :delete, data: [confirm: gettext("Are you sure?")], class: "btn btn-delete #{delete_creature_class(creature)}" %>
67. Removendo dependências defmodule CatchEmAllWeb.CreatureController do def delete(conn, %{"id" => id}) do creature = Games.get_creature!(id) {:ok, _creature} = Games.delete_creature(creature) :ok = Notifications.creature_deleted(creature) conn |> put_flash(:info, "Creature now rests in peace.") |> redirect(to: creature_path(conn, :index)) end end
68. Removendo dependências defmodule CatchEmAllWeb.CreatureController do def delete(conn, %{"id" => id}) do creature = Games.get_creature!(id) {:ok, _creature} = Games.delete_creature(creature) :ok = Notifications.creature_deleted(creature) conn |> put_flash(:info, "Creature now rests in peace.") |> redirect(to: creature_path(conn, :index)) end end
69. Removendo dependências defmodule CatchEmAllWeb.CreatureController do def delete(conn, %{"id" => id}) do creature = Games.get_creature!(id) {:ok, _creature} = Games.delete_creature(creature) :ok = Notifications.creature_deleted(creature) conn |> put_flash(:info, "Creature now rests in peace.") |> redirect(to: creature_path(conn, :index)) end end
70. Removendo dependências defmodule CatchEmAll.Games do import Ecto.Query, warn: false alias CatchEmAll.Repo alias CatchEmAll.Games.Creature def get_creature!(id), do: Repo.get!(Creature, id) def delete_creature(%Creature{} = creature) do Repo.delete(creature) end end
71. Removendo dependências defmodule CatchEmAll.Games do import Ecto.Query, warn: false alias CatchEmAll.Repo alias CatchEmAll.Games.Creature def get_creature!(id), do: Repo.get!(Creature, id) def delete_creature(%Creature{} = creature) do Repo.delete(creature) end end
72. Removendo dependências defmodule CatchEmAllWeb.CreatureController do def delete(conn, %{"id" => id}) do creature = Games.get_creature!(id) {:ok, _creature} = Games.delete_creature(creature) :ok = Notifications.creature_deleted(creature) conn |> put_flash(:info, "Creature now rests in peace.") |> redirect(to: creature_path(conn, :index)) end end
73. Removendo dependências defmodule CatchEmAllWeb.CreatureController do def delete(conn, %{"id" => id}) do creature = Games.get_creature!(id) {:ok, _creature} = Games.delete_creature(creature) :ok = Notifications.creature_deleted(creature) conn |> put_flash(:info, "Creature now rests in peace.") |> redirect(to: creature_path(conn, :index)) end end
74. Removendo dependências defmodule CatchEmAll.Notifications do def creature_deleted(creature) do # Deliver async messages end end
75. Removendo dependências defmodule CatchEmAll.Notifications do def creature_deleted(creature) do # Deliver async messages end end
76. Removendo dependências defmodule CatchEmAllWeb.CreatureController do def delete(conn, %{"id" => id}) do creature = Games.get_creature!(id) {:ok, _creature} = Games.delete_creature(creature) :ok = Notifications.creature_deleted(creature) conn |> put_flash(:info, "Creature now rests in peace.") |> redirect(to: creature_path(conn, :index)) end end
77. Removendo dependências defmodule CatchEmAllWeb.CreatureController do def delete(conn, %{"id" => id}) do creature = Games.get_creature!(id) {:ok, _creature} = Games.delete_creature(creature) :ok = Notifications.creature_deleted(creature) conn |> put_flash(:info, "Creature now rests in peace.") |> redirect(to: creature_path(conn, :index)) end end
78. Removendo dependências defmodule CatchEmAll.Games do import Ecto.Query, warn: false alias CatchEmAll.Repo alias CatchEmAll.Games.Creature def get_creature!(id), do: Repo.get!(Creature, id) def delete_creature(%Creature{} = creature) do Repo.delete(creature) end end
79. Removendo dependências defmodule CatchEmAll.Games do import Ecto.Query, warn: false alias CatchEmAll.Repo alias CatchEmAll.Games.Creature def get_creature!(id), do: Repo.get!(Creature, id) def delete_creature(%Creature{} = creature) do Repo.delete(creature) end end
80. Removendo dependências defmodule CatchEmAllWeb.CreatureController do def delete(conn, %{"id" => id}) do creature = Games.get_creature!(id) {:ok, _creature} = Games.delete_creature(creature) :ok = Notifications.creature_deleted(creature) conn |> put_flash(:info, "Creature now rests in peace.") |> redirect(to: creature_path(conn, :index)) end end
81. Removendo dependências defmodule CatchEmAllWeb.CreatureController do def delete(conn, %{"id" => id}) do creature = Games.get_creature!(id) {:ok, _creature} = Games.delete_creature(creature) :ok = Notifications.creature_deleted(creature) conn |> put_flash(:info, "Creature now rests in peace.") |> redirect(to: creature_path(conn, :index)) end end
82. Removendo dependências defmodule CatchEmAllWeb.CreatureController do def delete(conn, %{"id" => id}) do creature = Games.get_creature!(id) {:ok, _creature} = Games.delete_creature(creature) :ok = Notifications.creature_deleted(creature) conn |> put_flash(:info, "Creature now rests in peace.") |> redirect(to: creature_path(conn, :index)) end end
83. Removendo dependências defmodule CatchEmAllWeb.CreatureController do def delete(conn, %{"id" => id}) do creature = Games.get_creature!(id) {:ok, _creature} = Games.delete_creature(creature) :ok = Notifications.creature_deleted(creature) conn |> put_flash(:info, "Creature now rests in peace.") |> redirect(to: creature_path(conn, :index)) end end
84. Removendo dependências defmodule CatchEmAllWeb.CreatureController do end
85. Removendo dependências <%= link gettext("Sacrifice %{creature} </3", creature: creature.nickname), to: creature_path(@conn, :delete, creature), method: :delete, data: [confirm: gettext("Are you sure?")], class: "btn btn-delete #{delete_creature_class(creature)}" %>
86. Removendo dependências <%= link gettext("Sacrifice %{creature} </3", creature: creature.nickname), to: creature_path(@conn, :delete, creature), method: :delete, data: [confirm: gettext("Are you sure?")], class: "btn btn-delete #{delete_creature_class(creature)}" %>
87. Removendo dependências ## default.pot msgid "" msgstr "" #: lib/catch_em_all_web/templates/creature/index.html.eex:23 msgid "Are you sure?" msgstr "" #: lib/catch_em_all_web/templates/creature/index.html.eex:20 msgid "Sacrifice %{creature} </3" msgstr ""
88. Removendo dependências ## default.pot msgid "" msgstr "" #: lib/catch_em_all_web/templates/creature/index.html.eex:23 msgid "Are you sure?" msgstr "" #: lib/catch_em_all_web/templates/creature/index.html.eex:20 msgid "Sacrifice %{creature} </3" msgstr ""
89. Removendo dependências ## default.pot msgid "" msgstr ""
90. Removendo dependências <%= link gettext("Sacrifice %{creature} </3", creature: creature.nickname), to: creature_path(@conn, :delete, creature), method: :delete, data: [confirm: gettext("Are you sure?")], class: "btn btn-delete #{delete_creature_class(creature)}" %>
91. Removendo dependências <%= link gettext("Sacrifice %{creature} </3", creature: creature.nickname), to: creature_path(@conn, :delete, creature), method: :delete, data: [confirm: gettext("Are you sure?")], class: "btn btn-delete #{delete_creature_class(creature)}" %>
92. Removendo dependências defmodule CatchEmAllWeb.Router do use CatchEmAllWeb, :router pipeline :browser do # ... end scope "/", CatchEmAllWeb do pipe_through :browser resources "/creatures", CreatureController end end
93. Removendo dependências defmodule CatchEmAllWeb.Router do use CatchEmAllWeb, :router pipeline :browser do # ... end scope "/", CatchEmAllWeb do pipe_through :browser resources "/creatures", CreatureController end end
94. Removendo dependências defmodule CatchEmAllWeb.Router do use CatchEmAllWeb, :router pipeline :browser do # ... end scope "/", CatchEmAllWeb do pipe_through :browser resources "/creatures", CreatureController, except: [:delete] end end
95. Removendo dependências <%= link gettext("Sacrifice %{creature} </3", creature: creature.nickname), to: creature_path(@conn, :delete, creature), method: :delete, data: [confirm: gettext("Are you sure?")], class: "btn btn-delete #{delete_creature_class(creature)}" %>
96. Removendo dependências <%= link gettext("Sacrifice %{creature} </3", creature: creature.nickname), to: creature_path(@conn, :delete, creature), method: :delete, data: [confirm: gettext("Are you sure?")], class: "btn btn-delete #{delete_creature_class(creature)}" %>
97. Removendo dependências defmodule CatchEmAllWeb.CreatureView do use CatchEmAllWeb, :view def delete_creature_class(%{active: true}), do: "btn-warn" def delete_creature_class(%{active: false}), do: "btn-info" end
98. Removendo dependências defmodule CatchEmAllWeb.CreatureView do use CatchEmAllWeb, :view def delete_creature_class(%{active: true}), do: "btn-warn" def delete_creature_class(%{active: false}), do: "btn-info" end
99. Removendo dependências defmodule CatchEmAllWeb.CreatureView do use CatchEmAllWeb, :view end
100. Removendo dependências <%= link gettext("Sacrifice %{creature} </3", creature: creature.nickname), to: creature_path(@conn, :delete, creature), method: :delete, data: [confirm: gettext("Are you sure?")], class: "btn btn-delete #{delete_creature_class(creature)}" %>
101. Removendo dependências <%= link gettext("Sacrifice %{creature} </3", creature: creature.nickname), to: creature_path(@conn, :delete, creature), method: :delete, data: [confirm: gettext("Are you sure?")], class: "btn btn-delete #{delete_creature_class(creature)}" %>
102. Removendo dependências $('.creature-actions').on('click', '.btn-delete', event => { this.trackAnalyticsMagic(event.target); });
103. Removendo dependências $('.creature-actions').on('click', '.btn-delete', event => { this.trackAnalyticsMagic(event.target); });
104. Removendo dependências $('.creature-actions').on('click', '.btn-delete', event => { this.trackAnalyticsMagic(event.target); });
105. Removendo dependências $('.creature-actions').on('click', '.btn-delete', event => { this.trackAnalyticsMagic(event.target); });
106. Removendo dependências .creature-actions .btn-delete { background-color: #ccc; }
107. Removendo dependências .creature-actions .btn-delete { background-color: #ccc; }
108. Removendo dependências <%= link gettext("Sacrifice %{creature} </3", creature: creature.nickname), to: creature_path(@conn, :delete, creature), method: :delete, data: [confirm: gettext("Are you sure?")], class: "btn btn-delete #{delete_creature_class(creature)}" %>
109. Removendo dependências <%= link gettext("Sacrifice %{creature} </3", creature: creature.nickname), to: creature_path(@conn, :delete, creature), method: :delete, data: [confirm: gettext("Are you sure?")], class: "btn btn-delete #{delete_creature_class(creature)}" %>
110. Feito! ✨ ' ✨ ✨
111. Ferramentas ajudam https:/ /unused.codes/
112. Ferramentas ajudam
113. Ferramentas ajudam
114. Checklist das dependências • CSS, JavaScript, Imagens, assets em geral • Chaves de cache de longa expiração • Tarefas assíncronas • mix.exs • Arquivos de configuração, I18n • Documentação, README, etc. • Receitas de provisionamento • Banco de dados: migrações, tabelas, colunas, views, triggers, etc. • Testes: cases compartilhados, helpers, etc.
115. CSS, JavaScript, Imagens…
116. Chaves de cache
117. Tarefas assíncronas
118. Bibliotecas externas e mix.exs
119. Arquivos de configuração
120. Documentação, README
121. Receitas de provisionamento
122. Banco de dados • Colunas • Índices • Tabelas • Views • Triggers • Migrations
123. Testes • Shared setup/cases • Shared helpers • Factories • Fixtures
124. Checklist das dependências • CSS, JavaScript, Imagens, assets em geral • Chaves de cache de longa expiração • Tarefas assíncronas • mix.exs • Arquivos de configuração, I18n • Documentação, README, etc. • Receitas de provisionamento • Banco de dados: migrações, tabelas, colunas, views, triggers, etc. • Testes: cases compartilhados, helpers, etc.
125. Código tem preço, podemos ganhar mais fazendo menos
126. Escreva seu código pensando no dia de apagá-lo
128. Remover código não é tão simples quanto parece
129. Obrigado! britto noteu
130. Fontes e referências • The Pink Panther in “Pink Outs” • https:/ /youtu.be/1q2hu-mDtKs • Jenga® • https:/ /en.wikipedia.org/wiki/Jenga • Information is beautiful - Codebases • http:/ /www.informationisbeautiful.net/visualizations/million-lines-of-code/ • Feature Creep • https:/ /twitter.com/wakeupmrkim/status/925427903352922114 • Grant Ammons - Killing features — just as important as building them • https:/ /medium.com/@gammons/killing-features-just-as-important-as-building- them-7f4d64223585
131. Fontes e referências • Sandi MacPherson - Tough tradeoffs: Removing product features is hard, but often necessary • https:/ /thenextweb.com/dd/2015/01/18/tough-tradeoffs-removing-product-features- hard-often-necessary/ • Jeff Atwood - The Best Code is No Code At All • https:/ /blog.codinghorror.com/the-best-code-is-no-code-at-all/ • Edsger W. Dijkstra - EWD 1036 • https:/ /www.cs.utexas.edu/~EWD/transcriptions/EWD10xx/EWD1036.html • Mike Perham - Kill Your Dependencies • http:/ /www.mikeperham.com/2016/02/09/kill-your-dependencies/ • Thomas Figg - Write code that is easy to delete, not easy to extend. • https:/ /programmingisterrible.com/post/139222674273/write-code-that-is-easy-to- delete-not-easy-to
132. Fontes e referências • Sandi Metz - Practical Object-Oriented Design in Ruby • http:/ /www.poodr.com/ • Maslow’s Trapezoid of Code Cleaniness • https:/ /twitter.com/KellySutton/status/847875703383117824 • https:/ /twitter.com/compooter/status/847881828224684032 • Refactoring code • https:/ /twitter.com/olarclara/status/928802983130927104 • Ned Batchelder - Deleting code • https:/ /nedbatchelder.com/text/deleting-code.html • Tree Shaking • http:/ /gph.is/2pPEHXx
133. Fontes e referências • Rollup.js • https:/ /rollupjs.org/ • Unused • https:/ /unused.codes/ • Exercism • http:/ /exercism.io/ • Google Chrome Dev Tools Code Coverage Tab • https:/ /developers.google.com/web/updates/2017/04/devtools-release- notes#coverage • Programming skills • https:/ /twitter.com/stephentyrone/status/930825774818455553 • Imagens de arquivo pessoal