Set up config_accessor with a default value by block

[larrylv]

• ActiveSupport::Configurable should allow config_accessor to take
  default value by block, just like cattr_accessor.

    class User
      include ActiveSupport::Configurable
      config_accessor :hair_colors do
        [:brown, :black, :blonde, :red]
      end
    end
  
    User.hair_colors # => [:brown, :black, :blonde, :red]
  

• remove trailing whitespaces in configurable.rb and its test file.

It's an old pull request #5730, but no one implement it . I just implement it like someone suggested, change the interface to just like cattr_accessor.

[larrylv]

cc @steveklabnik @schneems

[carlosantoniodasilva]

It seems ok to me, although I don't see a real gain from one over another:

config_accessor :hair_colors do
  [:brown, :black, :blonde, :red]
end

# vs

config_accessor :hair_colors
self.hair_colors = [:brown, :black, :blonde, :red]

In any case, your pull request needs a changelog entry as well. Thanks!

[larrylv]

@carlosantoniodasilva I have updated ActiveSuppport's CHANGELOG.

[robin850]

@larrylv : just rebase your commits squashing them into a single one. :)

[larrylv]

@robin850 then do I have to open another pull request or just git push -f?

[robin850]

@larrylv : once your commits are squashed, just push with -f. :) You don't have to open a new pull request, it will be automatically updated.

[larrylv]

@robin850 Thx. Already done that. :-)

[robin850]

I allow myself to ping @carlosantoniodasilva to merge this. ^^

[carlosantoniodasilva]

@larrylv thanks, but I'll have to ask you to do one more thing: can you amend your commit and move the changelog entry to the top, please? We usually put them on the top. Thanks!

@robin850 thanks!

[larrylv]

@carlosantoniodasilva Sorry, my mistake. Already moved changelog entry to the top.

[carlosantoniodasilva]

Great! Now github is telling me: This pull request cannot be automatically merged.. I think you'll need to rebase :)

[larrylv]

@carlosantoniodasilva Done with rebase. Please check it out. :)

[rafaelfranca]

Thanks.

[zires]

I am curious about why use block to define default value.The default option can take care of this, like:

config_accessor :hair_colors, default: [:brown, :black, :blonde, :red]

[larrylv]

@zires I don't think config_accessor supports default option. U can check the config_accessor method here https://github.com/rails/rails/blob/master/activesupport/lib/active_support/configurable.rb#L106 . It doesn't do anything about default. And also I write test codes below to double check.

require 'active_support'

person = Class.new do
    include ActiveSupport::Configurable
    config_accessor :hair_colors, default: [:brown, :black, :blonde]
end

person.hair_colors # => nil

And the reason I choose to use block to define default value is cattr_accessor uses block to define it. U can check it here. https://github.com/rails/rails/blob/master/activesupport/lib/active_support/core_ext/class/attribute_accessors.rb#L32

In some way, they are very alike.

[bobbytables]

I think a block to always define a default value is weird (and more expensive). Why not have a default: key?

[zires]

@bobbytables That is what i mean