I18n custom exception handler isn't called with `t`, only with `I18n.translate`

Question

I have this custom exception handler:

module I18n
  class MissingTanslationsCollectorExceptionHandler < I18n::ExceptionHandler
    # Handles exceptions from I18n
    def call(exception, locale, key, options)
      if exception.is_a?(I18n::MissingTranslation)
        binding.pry
        missing_translations << I18n.normalize_keys(locale, key, options[:scope])
        super
      end
    end
  end
end

I assign it like this:

I18n.exception_handler = I18n::MissingTanslationsCollectorExceptionHandler.new

When using the console, it seems to work:

$ rails c
Loading development environment (Rails 4.2.0)

[1] base »  I18n.exception_handler
=> #<I18n::MissingTanslationsCollectorExceptionHandler:0x00000101c121e8>
[2] base »  I18n.translate 'unknown'

From: /Users/josh/Documents/Work/MuheimWebdesign/base/src/lib/missing_i18n_exception_handler.rb @ line 11 I18n::MissingTanslationsCollectorExceptionHandler#call:

    10:   if exception.is_a?(I18n::MissingTranslation)
 => 11:     binding.pry
    12:     missing_translations << I18n.normalize_keys(locale, key, options[:scope])

[1] base(#<I18n::MissingTanslationsCollectorExceptionHandler>) »  c
=> "translation missing: en.unknown"

But when starting the server and hitting a missing translation with t 'unknown', binding.pry isn't called. Only when doing a I18n.translateunknown`, it is called. Why?

Maybe it has to do with the fact that the feature specs are run inside their own process using Capybara?

Update

Here is the Rails app in question: https://github.com/jmuheim/base/tree/features/custom-i18n-exception-handler

I have added the custom i18n exception handler here: https://github.com/jmuheim/base/commit/f2aff30046c7a9f38c4a1faed0953e474099120c

And I have added code which should demonstrate the issue here: https://github.com/jmuheim/base/commit/af484b6b96f41194043e0ad0668a5c288d4a0af3

Simply go the to root_path, then it should be triggered (once, not twice!).

Answer 1

This happens because ActionView's t isn't a simple alias to I18n.translate. Among other things, it converts any MissingTranslation exceptions to spans in your HTML.

See the code for details.

I wanted exceptions to bubble up, but I didn't want to have to specify rescue_format: true every time I called t in my views, so I overrode Rails's helper to always pass rescue_format: true as an option.

Another thing to note: the translation helper has changed a bit from one Rails version to the next, so make sure you read the actual code for your version to see what to do.