Ruby I18n Debug

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Ever wondered which translations are being looked up by Rails, a gem, or simply your app? Wonder no more!

Rails' implicit translations, for instance, are a nice feature. But sometimes getting the key to, let's say, the BillingAddress' street attribute in a nested form inside an Order can be quite tricky to get right on the first try. The key for this example would be activerecord.attributes.order/billing_address.street. Good luck figuring that out!

With this gem you can easily see which translations are being looked up. The key above would have created the following debug log entry:

[i18n-debug] activerecord.attributes.order/ => nil

After setting the translation for that key you just discovered, the log entry changes to this:

[i18n-debug] activerecord.attributes.order/ => "Order billing name"


Simply add the gem to your Gemfile. You probably only want this in development. Thus, place it inside the development group.

gem 'i18n-debug', group: :development

If you need support for ruby <= 2.0, make sure to use version 1.0.0.


This gem works straight out of the box. If Rails is available, it will log using Rails.logger.debug. Otherwise it will log using$stdout).debug.

If you wish to use a custom logger, simply set it as follows (make sure it responds to debug):

I18n::Debug.logger = my_custom_logger

Every lookup invokes the lambda I18n::Debug.on_lookup with the key and the translation value as arguments. The default lambda simply logs it to the logger mentioned above. If you want to change the logging format or do something totally different, simply set your own handler to do so:

# Collect stats on I18n key usage.
i18n_stats = { |stats, key| stats[key] = 0 }

I18n::Debug.on_lookup do |key, value|
  i18n_stats[key] += 1 if value

Additional Information



Philipe Fatio (fphilipe)


MIT License. Copyright 2014 Philipe Fatio