[ruby-core:56647] Re: [ruby-trunk - Feature #8781] Use require_relative() instead of require() if possible

Em 16-08-2013 03:24, Aaron Patterson escreveu:
> On Fri, Aug 16, 2013 at 03:00:59PM +0900, SASADA Koichi wrote:
>> (2013/08/16 14:21), Aaron Patterson wrote:
>>> If you move the file, then all calls to `require_relative` in that file
>>> must be changed.  If you had just used `require`, the file can be moved
>>> without changes.
>> Which case?
>>
>> For example, there are files:
>>    foo.rb
>>    foo/bar/a.rb
>>
>> And foo.rb has "require 'foo/bar/a'".
>>
>> If you move foo/bar/a.rb to foo/bar/b.rb, then you need to rewrite to
>> "require 'foo/bar/b'".
>>
>> If you move foo/bar/a.rb to foo/baz/a.rb, then you need to rewrite to
>> "require 'foo/baz/a'".
> Yes, you changed the files that *depend on* the source for 'foo/bar/a',
> but 'foo/bar/a.rb' itself did not change.
>
> If something *you depend on* changes location, then yes, you should
> change your code.
>
> Here is an example with require_relative:
>
> $ mkdir -p lib/foo/bar
> $ touch lib/foo.rb
> $ echo "require_relative '../../foo'" > lib/foo/bar/baz.rb
> $ ruby -I lib -r'foo/bar/baz' -e 0
> $ mv lib/foo/bar/baz.rb lib/foo/
> $ ruby -I lib -r'foo/baz' -e 0
> /Users/aaron/git/example/lib/foo/baz.rb:1:in `require_relative': cannot load such file -- /Users/aaron/git/example/foo (LoadError)
>          from /Users/aaron/git/example/lib/foo/baz.rb:1:in `<top (required)>'
>          from /Users/aaron/.rbenv/versions/2.0.0-p247/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:45:in `require'
>          from /Users/aaron/.rbenv/versions/2.0.0-p247/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:45:in `require'
> $
>
> In the above example, "foo.rb" did not change location, yet I have to
> change the call to `require_relative`.
>
> foo/bar/baz.rb depends on foo.rb.  foo.rb did not change locations, so
> why do I have to change my code?
>
> Let's take the same example, "foo/bar/baz.rb" that depends on "foo.rb",
> but instead use `require`:
>
> $ mkdir -p lib/foo/bar
> $ echo "require 'foo'" > lib/foo/bar/baz.rb
> $ touch lib/foo.rb
> $ ruby -I lib -r'foo/bar/baz' -e 0
> $ mv lib/foo/bar/baz.rb lib/foo/
> $ ruby -I lib -r'foo/baz' -e 0
> $
>
> My dependency, "foo.rb", did not change locations, so I don't need to
> change my code.  "foo/bar/baz.rb" works as-is, no matter where it is on
> the filesystem. :-)
>

Since we were discussing the design perspective, you just demonstrated 
how the design of using require can become much worse than using 
require_relative. When you're reading code you can be sure where to look 
for the files being loaded as expected while when using require you will 
always have to check $LOAD_PATH to be sure. I don't really think using 
require to allow such hacks is a good enough reason to favor require 
instead of require_relative... After all, Ruby already allows you to 
override code by monkey patching. Why would you need to override a full 
file?