[question] Can I install JRuby/CRuby specific gem with add_dependency?

[hiroyuki-sato]

Hello

Is it possible to write gemspec like the following.

• On JRuby, install 'jrjackson' gem.
• On CRuby, install 'oj' gem.

The develop wrote following code, But I got following error on JRuby platform.
It install Oj gem.

https://github.com/sisimai/rb-Sisimai

gemspec file.

  if RUBY_PLATFORM =~ /java/
    spec.add_runtime_dependency 'jrjackson', '>= 0.3.8'
  else
    spec.add_runtime_dependency 'oj', '>= 2.14.4'
  end

gem install sisimai
Building native extensions.  This could take a while...
ERROR:  Error installing sisimai:
    ERROR: Failed to build gem native extension.

    /path/to/home/.rbenv/versions/jruby-9.0.4.0/bin/jruby -r ./siteconf20160216-35142-198flf6.rb extconf.rb
NotImplementedError: C extensions are not supported
    <top> at /path/to/home/.rbenv/versions/jruby-9.0.4.0/lib/ruby/stdlib/mkmf.rb:1
  require at org/jruby/RubyKernel.java:939
   (root) at /path/to/home/.rbenv/versions/jruby-9.0.4.0/lib/ruby/stdlib/rubygems/core_ext/kernel_require.rb:1
    <top> at extconf.rb:1

extconf failed, exit code 1

Gem files will remain installed in /path/to/home/.rbenv/gems/2.2.0/gems/oj-2.14.4 for inspection.
Results logged to /path/to/home/.rbenv/gems/2.2.0/extensions/universal-java-1.8/2.2.0/oj-2.14.4/gem_make.out

Current workaround, write Gemfile the following.

gem 'oj', '>= 2.14.4', :platform => :ruby
gem 'jrjackson', '>= 0.3.8', :platform => :jruby

It worked but, does not install 'oj' or 'jrjackson' gem.

Gem version is 2.5.2.

Any idea?

[segiddins]

This is currently a limitation of RubyGems -- if you want platform-specific dependencies, you will have to release platform-specific versions of your own gem

[hiroyuki-sato]

@segiddins Thanks. I understand.

Please tell me one more thing.
Do you have any idea or example to make two gems in single project?
Like the following

• project.gemspec generate project.gem
• project-java.gemspec generate project-java.gem

Thanks.

[copiousfreetime]

@hiroyuki-sato the easiest way, you would have 2 .gemspec files, one for the ruby gem and one for the java gem. Then you would build them gems like:

• gem build project.gemspec would create project.gem
• gem build project-java.gemspec would create project-java.gem

The two gemspecs would be virtually identical except in the ruby one would have:

spec.add_dependency('oj', '~> 2.14')

and the jruby one would have

 spec.add_dependency( 'jrjackson', '~> 0.3') 
 spec.platform = "java"

[hiroyuki-sato]

@chancancode Thank you for your advice. I created two gem files.
I'm using bundler. but bundler don't support multiple gemspec files in same directory.
I'll check gem command for publish gem without bundler .