Restclient throwing unusual exception - ruby

Question

While trying to use the following gems:
require 'nokogiri'
require 'restclient'
require 'mechanize'
I'm getting the following error:
C:/Ruby23/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require': cannot load such file -- ffi_c (LoadError)
from C:/Ruby23/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from C:/Ruby23/lib/ruby/gems/2.3.0/gems/ffi-1.9.10-x86-mingw32/lib/ffi.rb:6:in `rescue in <top (required)>'
from C:/Ruby23/lib/ruby/gems/2.3.0/gems/ffi-1.9.10-x86-mingw32/lib/ffi.rb:3:in `<top (required)>'
from C:/Ruby23/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from C:/Ruby23/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from C:/Ruby23/lib/ruby/gems/2.3.0/gems/rest-client-1.8.0-x86-mingw32/lib/restclient/windows/root_certs.rb:2:in `<top (required)>'
from C:/Ruby23/lib/ruby/gems/2.3.0/gems/rest-client-1.8.0-x86-mingw32/lib/restclient/windows.rb:7:in `require_relative'
from C:/Ruby23/lib/ruby/gems/2.3.0/gems/rest-client-1.8.0-x86-mingw32/lib/restclient/windows.rb:7:in `<top (required)>'
from C:/Ruby23/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from C:/Ruby23/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from C:/Ruby23/lib/ruby/gems/2.3.0/gems/rest-client-1.8.0-x86-mingw32/lib/restclient.rb:16:in `<top (required)>'
from C:/Ruby23/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:133:in `require'
from C:/Ruby23/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:133:in `rescue in require'
from C:/Ruby23/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:40:in `require'
from parse_docs.rb:5:in `<main>'
Since the last thing on this list is line 5, which is require 'restclient' I'm guessing it has something to do with that? However I've attempted to do the following:
Since restclient is deprecated and has moved to rest-client, I tried using rest-client however that doesn't work and produces the same error.
I've also attempted to require 'rubygems' but that when I run the program, it will not allow me to continue and produces the same error.
So I completely took out restclient, this is how I got the idea that restclient is causing the problem , because without it there, the program can run successfully.
So I though what would happen if I rolled back on ffi? So I installed the ffi version that is needed to run restclient However, that didn't help either.
Updated all my gems, still throwing the same error..
Downloaded the latest version on ffi, nothing changes, except now I havea new version of ffi on my system, that's still throwing an error when being used with restclient
Why is restclient producing the ffi error, I've never had this happen to me before. Is rest-client deprecated? Or is there a simple solution that I'm not catching onto? I've researched this, and nobody has had this problem (while using restclient) however there is a ton of people who have gotten this error while using other gems. For example see also here. It might also be worth mentioning that I'm running Windows 7.

Answer 1

The error comes after the ffi tries to load its C extension. If we have a look at the source code of the FFI gem, it tries to load the compiles extension according to the version of Ruby currently running:
begin
require RUBY_VERSION.split('.')[0, 2].join('.') + '/ffi_c'
rescue Exception
require 'ffi_c'
end
The first part fails so it falls back to the require 'ffi_c' which also fails. The problem now is that the first part should not fail.
In your case, it seems you are using a FFI gem which was compiled for another version of Ruby. Unfortunately, ruby has changes its ABI during releases so this doesn't work.
Thus, you need to make sure you are either using the pre-compiled gem matching your ruby version (which might be hard to find) or compiling it yourself. For that, please install the Development Kit for your Ruby version (towards the bottom left of the page). Then, you can install the ffi gem and force it to compile the C-extension on installation:
gem install ffi --platform=ruby
This is required as gem install ffi (without the --platform parameter), rubygems first tries to install the gem variant specific to your platform, i.e. mingw32 in your case, which is available in pre-compiled from from rubygems.org. Unfortunately, this precompiled gem apparently is incompatible with your version of Ruby. As such, you can force rubygems to get the source-version of the gem and compile the C-extension on its own. This is what you are instructing rubygems to do with the --platform=ruby argument.
This matches the description in the issues on FFI's issue tracker.

Answer 2

So I found an answer to this, it had to do with Holger Just's answer with a minor tweak, I'm pretty sure my case is pretty unique because my company likes to hide behind a VPN script. So here's how I did it:
First I needed to install the pre-release gem of ffi using the platform flag: gem install ffi --pre --platform=ruby
Next I had to update the gem: gem update --all (I think that's the correct syntax for the flag)
That got ffi working.