nokogiri - ERROR: Failed to build gem native exten

Question

I updated to the developer release of Lion and noticed I couldn't start rails apps anymore. Whenever I try to sudo bundle install, I get the following error:

Installing nokogiri (1.4.4) with native extensions /Library/Ruby/Site/1.8/rubygems/installer.rb:551:in `build_extensions': ERROR: Failed to build gem native extension. (Gem::Installer::ExtensionBuildError)

        /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby extconf.rb 
mkmf.rb can't find header files for ruby at /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/ruby.h


Gem files will remain installed in /Users/jamielawrence/Documents/Websites/atgdb/vendor/bundle/ruby/1.8/gems/nokogiri-1.4.4 for inspection.
Results logged to /Users/jamielawrence/Documents/Websites/atgdb/vendor/bundle/ruby/1.8/gems/nokogiri-1.4.4/ext/nokogiri/gem_make.out
    from /Library/Ruby/Site/1.8/rubygems/installer.rb:504:in `each'
    from /Library/Ruby/Site/1.8/rubygems/installer.rb:504:in `build_extensions'
    from /Library/Ruby/Site/1.8/rubygems/installer.rb:180:in `install'
    from /Library/Ruby/Gems/1.8/gems/bundler-1.0.15/lib/bundler/source.rb:101:in `install'
    from /Library/Ruby/Gems/1.8/gems/bundler-1.0.15/lib/bundler/rubygems_integration.rb:78:in `preserve_paths'
    from /Library/Ruby/Gems/1.8/gems/bundler-1.0.15/lib/bundler/source.rb:91:in `install'
    from /Library/Ruby/Gems/1.8/gems/bundler-1.0.15/lib/bundler/installer.rb:58:in `run'
    from /Library/Ruby/Gems/1.8/gems/bundler-1.0.15/lib/bundler/rubygems_integration.rb:93:in `with_build_args'
    from /Library/Ruby/Gems/1.8/gems/bundler-1.0.15/lib/bundler/installer.rb:57:in `run'
    from /Library/Ruby/Gems/1.8/gems/bundler-1.0.15/lib/bundler/spec_set.rb:12:in `each'
    from /Library/Ruby/Gems/1.8/gems/bundler-1.0.15/lib/bundler/spec_set.rb:12:in `each'
    from /Library/Ruby/Gems/1.8/gems/bundler-1.0.15/lib/bundler/installer.rb:49:in `run'
    from /Library/Ruby/Gems/1.8/gems/bundler-1.0.15/lib/bundler/installer.rb:8:in `install'
    from /Library/Ruby/Gems/1.8/gems/bundler-1.0.15/lib/bundler/cli.rb:222:in `install'
    from /Library/Ruby/Gems/1.8/gems/bundler-1.0.15/lib/bundler/vendor/thor/task.rb:22:in `send'
    from /Library/Ruby/Gems/1.8/gems/bundler-1.0.15/lib/bundler/vendor/thor/task.rb:22:in `run'
    from /Library/Ruby/Gems/1.8/gems/bundler-1.0.15/lib/bundler/vendor/thor/invocation.rb:118:in `invoke_task'
    from /Library/Ruby/Gems/1.8/gems/bundler-1.0.15/lib/bundler/vendor/thor.rb:246:in `dispatch'
    from /Library/Ruby/Gems/1.8/gems/bundler-1.0.15/lib/bundler/vendor/thor/base.rb:389:in `start'
    from /Library/Ruby/Gems/1.8/gems/bundler-1.0.15/bin/bundle:13
    from /usr/bin/bundle:19:in `load'
    from /usr/bin/bundle:19

Answer 1

I had similar problem, and after installing XCode 4.1, I also had to do the following command:

sudo port upgrade libxml2 libxslt

After that Nokogiri built without problems.

More info: http://tektastic.com/2011/07/ruby-mac-ports-and-os-x-lion.html

Answer 2

Install the ruby1.8-dev gem (or rather, the applicable *-dev gem), which will include all the header files. See: This question