Some very common files are loaded at the entry point of every component, to
avoid repeating their require again and again:
https://github.com/rails/rails/blob/master/activesupport/lib/active_support/rails.rb
As for the autoload + include, I don't really know, maybe it is a fancy way to
avoid writing a file path. Seems unnecessary to me at first glance. Maybe
someone else from the team has a better justification?
Sent from my iPhone
On 08/02/2013, at 17:45, Rodrigo Rosenfeld Rosas <[email protected]> wrote:
> Em 08-02-2013 13:03, Xavier Noria escreveu:
>>
>> On Fri, Feb 8, 2013 at 3:18 PM, Rodrigo Rosenfeld Rosas
>> <[email protected]> wrote:
>>
>>> Em 08-02-2013 12:06, Xavier Noria escreveu:
>>>
>>>> Seems unrelated to dependencies.rb, most likely a missing require
>>>> somewhere within Rails.
>>>>
>>>> It can be the case that it does not show up in production because of eager
>>>> loading.
>>>
>>> Any ideas why helpers.rb is loaded when you write code like below?
>>>
>>> module ActionView
>>> module Helpers
>>> module NumberHelper
>>>
>>> Is this normal MRI behavior or is this caused by dependencies.rb?
>> Ruby on Rails itself does not use dependencies.rb to load its code. It
>> is a regular Ruby library that uses requires and Kernel#autoload with
>> some added sugar. AS::Dependencies only covers application constant
>> autoloading.
>>
>> The thing goes like this: When an application boots in any environment
>> action_view.rb is loaded. When that file is executed an autoload for
>> :Helpers is configured under ActionView. In a default setup,
>> helpers.rb is not yet loaded. That is, if you run
>>
>> rails runner 1
>>
>> helpers.rb is not loaded (at least in 3-2-stable, not that we are
>> explaining any contract, only load order execution to follow what
>> happens in your exception).
>>
>> But if you force the evaluation of the constant as in your example above:
>>
>> module ActionView
>> module Helpers
>> ...
>> end
>> end
>>
>> that autoload is triggered because the interpreter checks whether
>> "Helpers" is a constant defined in the module object stored in
>> ActionView. Therefore, helpers.rb is interpreted and sets in turn an
>> autoload for NumberHelper below AV::Helpers.
>>
>> So, module Helpers in that snippet *reopens* a module object defined
>> via the autoload, rather than creating the module object. The
>> execution follows and the same happens with the "NumberHelper"
>> constant down below. The interpreter checks whether it belongs to the
>> module object stored in AV::Helpers. Since it is unknown and there is
>> an autoload for it it gets triggered, and loads... well the very
>> number_helper.rb whose execution we were in the middle of (not sure
>> this sentence is valid English :).
>>
>> I suspect there is a circularity here that is showing up that way.
>>
>> Would need to dig deeper to fully explain how this ends up in an
>> exception, maybe I'll do it tonight, but in the meantime here's some
>> context in case it helps.
>
> It makes total sense. What doesn't make sense is the source of helpers.rb to
> me:
>
> https://github.com/rails/rails/blob/master/actionpack/lib/action_view/helpers.rb
>
> First it should explicitly require (or require_dependency)
> 'active_support/autoload' and 'active_support/concern', right?
>
> But then, why using autoload if you're just including all modules next?
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