How to Eat a Whale

Transcript

1. HOW TO EAT A WHALE
   MAKING THE CHANGES YOU KNOW YOU NEED TO
   

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2. Have you heard of tiny Melinda Mae,
   Who ate a monstrous whale?
   She thought she could,
   She said she would,
   So she started in right at the tail.
   - Shel Silverstein
   

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3. not a criticism
   

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4. WE HAVE
   TO CHANGE
   

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5. ▸ Hard to Maintain
   ▸ New Features
   ▸ Better Performance
   ▸ Security
   ▸ Ergonomics
   ▸ Hiring
   

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6. RAILS 5 AS
   A CASE STUDY
   

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7. it’s a common
   upgrade
   

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8. ▸ 1.2 ➡ 4.2
   ▸ 3.0 ➡ 5.0
   ▸ 4.2 ➡ 5.0
   ▸ 4.2 ➡ 5.0
   success
   success
   failure
   ongoing!
   

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9. this works
   for other big changes
   

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10. WHY WE
    DON’T CHANGE
    

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11. the changes
    are ambiguous
    

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12. the risk
    is high
    

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13. it’s a lot
    of work
    

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14. source: git log -L 5,6:Gemfile
    Date Rails Version
    Jun ‘19 4.2.11
    Aug ‘17 4.2.7.1
    Dec ‘16 4.2.7
    Mar ‘16 4.1.13
    Mar ‘16 4.2.5.2
    Feb ‘16 4.2.5.1
    Aug ‘15 4.1.13
    Jan ‘15 4.1.9
    Dec ‘14 4.0.0
    … …
    May ‘13 3.2.8
    

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15. but there
    is hope!
    

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16. 1. REDUCE AMBIGUITY
    

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17. try to get a
    list of changes
    

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18. ▸ changelogs
    ▸ upgrade guide
    ▸ gem dependency graph
    ▸ try changes and see what explodes
    

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21. uncover sneaky
    problems
    

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22. # old
    class FactoryGirl
    # new
    class FactoryBot
    

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23. class Money::Arithmetic
    def ==(other)
    # don’t allow comparison w/ non-Money objects
    unless other.is_a? Money || other.zero?
    raise ArgumentError
    end
    # ... do comparison
    end
    end
    

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24. class Money::Arithmetic
    def ==(other)
    # warn about problems
    if other.is_a?(Numeric) && other.nonzero?
    trigger_warning_and_rollbar
    end
    super # run actual comparison
    end
    end
    

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25. keep strong
    test coverage
    

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26. 2. REDUCE RISK
    

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27. take tiny steps
    

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28. ‣ rails 5
    
    ‣ factory_bot
    
    ‣ belongs_to
    
    ‣ protected_attributes
    
    ‣ strong params
    
    ‣ activeadmin
    
    ‣ devise
    
    ‣ upgrade ruby
    
    ‣ rails 4.2.11
    
    ‣ sass
    
    ‣ coffee
    
    ‣ money
    
    ‣ etc…
    
    ‣ quiet_assets*
    

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29. ‣ factory bot
    
    ‣ add shim
    
    ‣ use shim for existing cases
    
    ‣ upgrade factory girl to most recent version
    
    ‣ switch to factory bot and remove shim
    lots of changes, low risk
    tiny change, highest risk
    

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31. update code,
    then dependency
    

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32. FactoryBot.define AtlRollout do
    # ...
    end
    

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33. # warning: BigDecimal.new is deprecated;
    # use BigDecimal() method instead.
    (BigDecimal.new('-50.00')..BigDecimal.new('50.00')) => 'cold',
    

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34. # in rails 4, this is optional
    # in rails 5, it’s required
    belongs_to :packing_facility
    # this works in both!
    belongs_to :packing_facility, required: false
    

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35. Make the change easy,
    Then make the easy change.
    - Kent Beck
    

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36. surface errors quickly,
    in the right place
    

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37. NoMethodError:
    undefined method 'sellout_limit' for nil:NilClass
    # ./app/models/meal.rb:531:in 'sellout_limit_for'
    # ./app/models/menu.rb:254:in 'meal_sold_out?'
    # ./app/models/meal_selection.rb:208:in 'validate_meal_selection'
    

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38. ArgumentError:
    Couldn’t find 3rd meal for plan 'Standard' in menu ’15-jul-2019'
    (2 meals for plan)
    # ./spec/factories/weekly_baskets.rb:131:in `validate_selection!'
    # ./spec/factories/weekly_baskets.rb:61:in `block (5 levels)’
    # ./spec/factories/weekly_baskets.rb:58:in `times'
    # ./spec/factories/weekly_baskets.rb:58:in `block (4 levels)’
    

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39. 3. REDUCE EFFORT
    

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40. it’s okay to be
    a bit clever
    

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41. # in rails 4, this is optional
    # in rails 5, it’s required
    belongs_to :packing_facility
    

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42. WeeklyBasket.reflect_on_all_associations.each do |association|
    next if association.macro != :belongs_to
    foreign_key_field = klass.reflections[association.name.to_s].foreign_key
    column = klass.columns.find { |c| c.name == foreign_key_field.to_s }
    required = association.options.fetch(:required, true) &&
    !association.options.fetch(:optional, false)
    if required && column.null
    exceptions << sprintf(“%-50s required, but column is nullable",
    "#{klass}##{association.name}")
    elsif !required && !column.null
    exceptions << sprintf("%-50s not required, but column is not nullable",
    "#{klass}##{association.name}")
    end
    end
    

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43. WeeklyBasket.reflect_on_all_associations.each do |association|
    end
    next if association.macro != :belongs_to
    foreign_key_field = klass.reflections[association.name.to_s].foreign_key
    column = klass.columns.find { |c| c.name == foreign_key_field.to_s }
    required = association.options.fetch(:required, true) &&
    !association.options.fetch(:optional, false)
    if required && column.null
    exceptions << sprintf(“%-50s required, but column is nullable",
    "#{klass}##{association.name}")
    elsif !required && !column.null
    exceptions << sprintf("%-50s not required, but column is not nullable",
    "#{klass}##{association.name}")
    end
    

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44. WeeklyBasket#address will be required, but column is nullable
    WeeklyBasket#meal_plan will be required, but column is nullable
    WeeklyBasket#shipping_box will be required, but column is nullable
    WeeklyBasket#shipping_region will be required, but column is nullable
    

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45. namespaces
    and shims
    

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46. class Money::Arithmetic
    def ==(other)
    if other.is_a?(Numeric) && other.nonzero?
    trigger_warning_and_rollbar
    end
    super
    end
    end
    

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48. namespace :rails_5 do
    task check_belongs_to_associations: :environment do
    silence_warnings do
    print "Eager Loading..."
    Rails.application.eager_load!
    puts “done.”
    # ... do comparison
    end
    end
    end
    

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49. do the
    hard work
    

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51. MOVING TARGETS:
    PEOPLE RISKS
    

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52. it's hard to
    relearn everything
    

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53. short lived
    changes (again)
    

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54. make it easier
    to do the right thing
    

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55. TO SUM THINGS UP
    

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56. ambiguity happens,
    risk happens,
    effort happens.
    but you
    minimize them
    

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58. THANKS!
    

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