[DRE-maint] Bug#710814: rubygems-integration: fails to override bin_path

[Kevin Locke]

On Wed, 2013-06-05 at 21:35 +0200, Paul van Tilburg wrote:
> On Sun, Jun 02, 2013 at 07:18:00PM +0200, Christian Hofstaedtler wrote:
>> there is a problem with rubygems-integration in which it fails to
>> properly override the binary path for gems.
>> 
>> This is mostly seen when having bin stubs from previously installed
>> gems in /usr/local/bin [...]
> 
> [...]
> 
> It seems that the problem occurs if a "older" gem with a program is
> installed while already the same but newer is installed via Debian and
> rubygem-intergration.  (That is why I explicitly install rake 0.9.0, while
> Debian Wheezy has 0.9.2.2.)

I think this issue also occurs on Jessie (and testing/unstable) when
installing a gem native extension.  To reproduce in a fresh chroot:

# apt-get -y install ruby
$ GEM_HOME=~/.gem gem install rainbow

This produces the following output on my system:

-8<-------------------------------------------------------------------
Building native extensions.  This could take a while...
ERROR:  Error installing rainbow:
	ERROR: Failed to build gem native extension.

    current directory: /home/user/.gem/gems/rainbow-2.2.2/ext
/usr/bin/ruby2.3 mkrf_conf.rb

current directory: /home/user/.gem/gems/rainbow-2.2.2/ext
/usr/bin/ruby2.3 -rubygems /usr/share/rubygems-integration/all/gems/rake-12.0.0/exe/rake RUBYARCHDIR=/home/user/.gem/extensions/x86_64-linux/2.3.0/rainbow-2.2.2 RUBYLIBDIR=/home/user/.gem/extensions/x86_64-linux/2.3.0/rainbow-2.2.2
/usr/bin/ruby2.3: No such file or directory -- /usr/share/rubygems-integration/all/gems/rake-12.0.0/exe/rake (LoadError)

rake failed, exit code 1

Gem files will remain installed in /home/user/.gem/gems/rainbow-2.2.2 for inspection.
Results logged to /home/user/.gem/extensions/x86_64-linux/2.3.0/rainbow-2.2.2/gem_make.out
-8<-------------------------------------------------------------------

Similar errors have been reported in some AskUbuntu questions:

https://askubuntu.com/q/872399
https://askubuntu.com/q/567423

The reason I think the issue is related to this bug is that the
problematic command line is built from Gem.bin_path at
lib/rubygems/ext/rake_builder.rb:23:

    "#{Gem.ruby} -rubygems #{Gem.bin_path('rake', 'rake')}"

Is there a workaround for installing gem native packages other than
`sudo gem install`?

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