[ruby-core:31469] [Feature #3608] Enhancing Pathname#each_child to be lazy

Feature #3608: Enhancing Pathname#each_child to be lazy
http://redmine.ruby-lang.org/issues/show/3608

Author: Tomasz Wegrzanowski
Status: Open, Priority: Normal

Right now it lists entire directory, then yields
every element, that is x.each_child(&b) means x.children.each(&b).

This is too slow for directories mounted over networked file systems etc.,
and there is currently no way to get lazy behaviour, other than leaving
convenient #each_child/#children API and moving to lower level.

With this patch:
* #children is eager like before, no change here
* #each_child becomes lazy
* #each_child without block returns lazy enumerator,
  so it can be used like this dir.each_child.find(&:symlink?)
  without losing laziness.

Patch is against trunk. pathname.rb was in lib/ not ext/pathname/lib/
before, but it works either way.

The part to return enumerator when called without a block wouldn't
work in 1.8. If backport is desired, that line would need to be thrown
away, and #children would need to build result array instead
of calling each_child(with_directory).to_a - this would be straightforward.


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