[ruby-core:102194] [Ruby master Feature#16978] Ruby should not use realpath for __FILE__

Issue #16978 has been updated by vo.x (Vit Ondruch).


Can this be resolved please? This is another scenario, which should work IMO, but it does not work:

~~~
$ mkdir a/
$ echo "require_relative 'b'" > a/test.rb
$ touch b.rb

$ ll
total 4
drwxrwxr-x. 1 vondruch vondruch 14 Jan 22 17:17 a
-rw-rw-r--. 1 vondruch vondruch  0 Jan 22 17:17 b.rb
lrwxrwxrwx. 1 vondruch vondruch  9 Jan 22 17:18 test.rb -> a/test.rb

$ ruby test.rb
Traceback (most recent call last):
	1: from test.rb:1:in `<main>'
test.rb:1:in `require_relative': cannot load such file -- /home/vondruch/tt/a/b (LoadError)
~~~

The point is that in the context of current directory, the `b.rb` is relative to `test.rb` and therefore this example should not work. It does not really matter that the `test.rb` is symlink. This behavior with `requie_relative` being more and more common basically prohibits usage of symlinks for Ruby code.

This is issue because gems typically does not ship their test suites. Therefore when testing packages in Fedora, we would like do something like:

~~~
$ gem unpack rspec-rails
Fetching rspec-rails-4.0.2.gem
Unpacked gem: '/home/vondruch/tt/rspec-rails-4.0.2'

$ cd rspec-rails-4.0.2/

# Link from git checkout or from separate archive
$ ln -s ~/projects/rspec/rspec-rails/spec/ .
~~~

This blows out as soon as `require_relative` is used in test suite, because it cannot refer back to `require_relative "../lib/rspec_rails"`, which expands to `/home/vondruch/projects/rspec/rspec-rails/spec/../lib/rspec_rails`, where there is either loaded completely different file or nothing. In Fedora [1], the test suite is typically extracted from tarball, so this would crash.

[1]: https://src.fedoraproject.org/rpms/rubygem-rspec-rails/blob/master/f/rubygem-rspec-rails.spec#_78

----------------------------------------
Feature #16978: Ruby should not use realpath for __FILE__
https://bugs.ruby-lang.org/issues/16978#change-90041

* Author: vo.x (Vit Ondruch)
* Status: Open
* Priority: Normal
----------------------------------------
This is the simplest test case:

~~~
$ mkdir a

$ echo "puts __FILE__" > a/test.rb

$ ln -s a b

$ ruby -Ib -e "require 'test'"
/builddir/a/test.rb
~~~

This behavior is problematic, because Ruby should not know nothing about the `a` directory. It was not instructed to use it. I should always refer to the file using the original path and do not dig into the underlying details, otherwise depending on file system setup, one might be forced to used `File.realpath` everywhere trying to use `__FILE__`.



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