When dealing with errors, ruby developers are encouraged to capture specific exceptions, but seeing which exceptions are currently configured (and thus possible) is a challenge, especially with exceptions being dynamically configured as gems are loaded.

The ExceptionsTree ruby gem provides adds both a rake task and a script which allows developers to see the Exceptions hierarchy configured for the application. If the application is based on Rails, this gem uses railties to tie in the rake task correctly. However, this gem also works fine with ruby scripts that are not Rails based.

The rake task is done with:

bundle exec rake exceptions

The script is invoked:

display_exceptions

The output can be quite long, as many applications have lots of gems that insert their own exceptions to the hierarchy. Of course, if you are searching for a particular exception, you can pipe the output through grep to find it. For example:

display_exceptions | grep IO    # _to find the IO exceptions_

Add this line to your application's Gemfile:

gem 'exceptions_tree'

And then execute:

$ bundle

Or install it yourself as:

$ gem install exceptions_tree

bundle exec rake exceptions

display_exceptions

After checking out the repo, run bin/setup to install dependencies. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/aks/exceptions_tree. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

The gem is available as open source under the terms of the MIT License.