I'm using the ruby gem charlock_holmes in a Rails 4 app to detect the character encodings of CSV's that I'm parsing so that CSV.foreach doesn't throw an error.
However, when I try to push to heroku (with gem 'charlock_holmes' in the Gemfile) I get the following error:
Installing charlock_holmes (0.6.9.4)
Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.
/tmp/build_e741f6ed-a860-47bf-8c0d-1b678fa0ebeb/vendor/ruby-2.0.0/bin/ruby extconf.rb
checking for main() in -licui18n... no
checking for main() in -licui18n... no
***************************************************************************************
*********** icu required (brew install icu4c or apt-get install libicu-dev) ***********
***************************************************************************************
*** 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=/tmp/build_e741f6ed-a860-47bf-8c0d-1b678fa0ebeb/vendor/ruby-2.0.0/bin/ruby
--with-icu-dir
--without-icu-dir
--with-icu-include
--without-icu-include=${icu-dir}/include
--with-icu-lib
--without-icu-lib=${icu-dir}/
--with-icui18nlib
--without-icui18nlib
--with-icui18nlib
--without-icui18nlib
Gem files will remain installed in /tmp/build_e741f6ed-a860-47bf-8c0d-1b678fa0ebeb/vendor/bundle/ruby/2.0.0/gems/charlock_holmes-0.6.9.4 for inspection.
Results logged to /tmp/build_e741f6ed-a860-47bf-8c0d-1b678fa0ebeb/vendor/bundle/ruby/2.0.0/gems/charlock_holmes-0.6.9.4/ext/charlock_holmes/gem_make.out
An error occurred while installing charlock_holmes (0.6.9.4), and Bundler cannot
continue.
Make sure that `gem install charlock_holmes -v '0.6.9.4'` succeeds before
bundling.
How do I get libicu-dev to install on Heroku?
Sadly the other two solutions don't work for me (see below), so I had to come up with my own solution. This solution works with Ruby 1.9.3 but hammady says it does not work with 2.0.0.
I used heroku-buildpack-multi:
heroku config:add BUILDPACK_URL=https://github.com/ddollar/heroku-buildpack-multi.git
With the following .buildpacks:
https://github.com/benjie/heroku-buildpack-apt
https://github.com/heroku/heroku-buildpack-ruby
And this Aptfile:
libicu-dev
My fork of heroku-buildpack-apt is required to export the BUNDLE_BUILD__CHARLOCK_HOLMES variable via Heroku's ENV_DIRs. In the Gemfile you just reference gem 'charlock_holmes' as usual and all works smoothly now for me.
If anyone can think of a way that doesn't involve exporting BUNDLE_BUILD__CHARLOCK_HOLMES then please let me know!
Ryan's answer doesn't work for me - Heroku bails because the bundle install step doesn't offer any output for 3 minutes. Silasj's answer references the frederick/heroku-buildpack-ruby buildpack which is no longer maintained and lags behind the official heroku-buildpack-ruby by quite an amount, which is not acceptable to me.