[ruby-core:56674] Re: [ruby-trunk - Feature #8781] Use require_relative() instead of require() if possible

On Sat, Aug 17, 2013 at 07:17:50AM +0900, trans (Thomas Sawyer) wrote:
> 
> Issue #8781 has been updated by trans (Thomas Sawyer).
> 
> 
> > $ echo "require_relative '../../foo'" > lib/foo/bar/baz.rb
> 
> Seriously? That is not a real use case. Proper use of require_relative is downward, not upward.

*sigh*

First, it *is* a real use case (as in, people actually use it in *real*
projects):

[aaron@higgins ruby (trunk)]$ git grep require_relative | grep '\.\.' | wc -l
      45
[aaron@higgins ruby (trunk)]$

If Ruby's source code isn't enough examples for you, try a GitHub seach:

  https://github.com/search?q=require_relative+..&type=Code&ref=searchresults

It's not up to you what is "proper" use.

Second, my point remains valid whether you go down or up.  Let's do
another example.

"foo.rb" depends on "foo/bar/baz.rb".

$ mkdir -p lib/foo/bar
$ touch lib/foo/bar/baz.rb
$ echo "require_relative 'foo/bar/baz'" > lib/foo.rb
$ ruby -I lib -rfoo -e 0
$ mv lib/foo.rb lib/foo/
$ ruby -I lib -rfoo/foo -e 0
/Users/aaron/git/example/lib/foo/foo.rb:1:in `require_relative': cannot load such file -- /Users/aaron/git/example/lib/foo/foo/bar/baz (LoadError)
        from /Users/aaron/git/example/lib/foo/foo.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'
$

If we move "foo.rb", we still have to change the call to
"require_relative" **even though the file we depend on did not change**.

Here is the same example just using `require`:

$ mkdir -p lib/foo/bar
$ echo "require 'foo/bar/baz'" > lib/foo.rb
$ touch lib/foo/bar/baz.rb
$ ruby -I lib -rfoo -e 0
$ mv lib/foo.rb lib/foo/
$ ruby -I lib -rfoo/foo -e 0
$

Again, "foo.rb" is completely independent of the filesystem.  The files
it depends on did not change, so it did not have to change.

I am uncertain how to make the coupling between "require_relative" and
the filesystem more clear than this.

-- 
Aaron Patterson
http://tenderlovemaking.com/