Passing build options to bundler

Problem

Have you ever had exception dusing installing gems through bundler like below?

Installing mysql2 (0.3.11) with native extensions
Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

        /usr/local/Cellar/rbenv/0.3.0/versions/1.9.3-p0/bin/ruby extconf.rb
checking for rb_thread_blocking_region()... yes
checking for rb_wait_for_single_fd()... yes
checking for mysql_query() in -lmysqlclient... no
checking for main() in -lm... yes
checking for mysql_query() in -lmysqlclient... no
checking for main() in -lz... yes
checking for mysql_query() in -lmysqlclient... no
checking for main() in -lsocket... no
checking for mysql_query() in -lmysqlclient... no
checking for main() in -lnsl... no
checking for mysql_query() in -lmysqlclient... no
checking for main() in -lmygcc... no
checking for mysql_query() in -lmysqlclient... no
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers.  Check the mkmf.log file for more
details.  You may need configuration options.

Provided configuration options:
  --with-opt-dir
  --without-opt-dir
  --with-opt-include
  --without-opt-include=${opt-dir}/include
  --with-opt-lib
  --without-opt-lib=${opt-dir}/lib
  --with-make-prog
  --without-make-prog
  --srcdir=.
  --curdir
  --ruby=/usr/local/Cellar/rbenv/0.3.0/versions/1.9.3-p0/bin/ruby
  --with-mysql-config
  --without-mysql-config
  --with-mysql-dir
  --without-mysql-dir
  --with-mysql-include
  --without-mysql-include=${mysql-dir}/include
  --with-mysql-lib
  --without-mysql-lib=${mysql-dir}/lib
  --with-mysqlclientlib
  --without-mysqlclientlib
  --with-mlib
  --without-mlib
  --with-mysqlclientlib
  --without-mysqlclientlib
  --with-zlib
  --without-zlib
  --with-mysqlclientlib
  --without-mysqlclientlib
  --with-socketlib
  --without-socketlib
  --with-mysqlclientlib
  --without-mysqlclientlib
  --with-nsllib
  --without-nsllib
  --with-mysqlclientlib
  --without-mysqlclientlib
  --with-mygcclib
  --without-mygcclib
  --with-mysqlclientlib
  --without-mysqlclientlib


Gem files will remain installed in /usr/local/Cellar/rbenv/0.3.0/versions/1.9.3-p0/lib/ruby/gems/1.9.1/gems/mysql2-0.3.11 for inspection.
Results logged to /usr/local/Cellar/rbenv/0.3.0/versions/1.9.3-p0/lib/ruby/gems/1.9.1/gems/mysql2-0.3.11/ext/mysql2/gem_make.out
An error occured while installing mysql2 (0.3.11), and Bundler cannot continue.
Make sure that `gem install mysql2 -v '0.3.11'` succeeds before bundling.

The problem solves by passing build options for this gem:

$ gem install mysql -v '0.3.10' -- --with-mysql-config=/usr/local/Cellar/mysql/5.5.20/bin/mysql_config

But this solution is ugly because you have to install problematic gems independently from bundler and if you have a lot of ruby versions in your operation system you will have to do it for each ruby version. But there is a another solution, much better this one.

Solution

Just type in the terminal:

bundle config build.mysql2  --with-mysql-config=/usr/local/Cellar/mysql/5.5.20/bin/mysql_config

And now you are able to install gems through bundler without issues:

bundler install

That’s it - you have installed all gems for your project. Full documentation is located here