module I18n::Base

I18n.exception_handler.call(exception, locale, key, options) # will be called like this
I18n.exception_handler = I18nExceptionHandler.new # an object

I18n.exception_handler.call(exception, locale, key, options) # will be called like this
I18n.exception_handler = lambda { |*args| ... } # a lambda

I18n.custom_exception_handler(exception, locale, key, options) # will be called like this
I18n.exception_handler = :custom_exception_handler # this is the default

Examples:

method #call will be called on the exception_handler object.
a method call. A Proc will simply be called. In any other case the
If exception_handler is a Symbol then it will simply be sent to I18n as

be raised or thrown (MissingTranslation).
which can be a Symbol, a Proc or any other Object unless they're forced to
Any exceptions thrown in translate will be sent to the @@exception_handler

def handle_exception(handling, exception, locale, key, options)
  case handling
  when :raise
    raise exception.respond_to?(:to_exception) ? exception.to_exception : exception
  when :throw
    throw :exception, exception
  else
    case handler = options[:exception_handler] || config.exception_handler
    when Symbol
      send(handler, exception, locale, key, options)
    else
      handler.call(exception, locale, key, options)
    end
  end
end