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# The Cascade module adds the ability to do cascading lookups to backends that
# are compatible to the Simple backend.
# By cascading lookups we mean that for any key that can not be found the
# Cascade module strips one segment off the scope part of the key and then
# tries to look up the key in that scope.
# E.g. when a lookup for the key :"" does not yield a result then
# the segment :bar will be stripped off the scope part :"" and the new
# scope :foo will be used to look up the key :baz. If that does not succeed
# then the remaining scope segment :foo will be omitted, too, and again the
# key :baz will be looked up (now with no scope).
# To enable a cascading lookup one passes the :cascade option:
# I18n.t(:'', :cascade => true)
# This will return the first translation found for :"", :"foo.baz"
# or :baz in this order.
# The cascading lookup takes precedence over resolving any given defaults.
# I.e. defaults will kick in after the cascading lookups haven't succeeded.
# This behavior is useful for libraries like ActiveRecord validations where
# the library wants to give users a bunch of more or less fine-grained options
# of scopes for a particular key.
# Thanks to Clemens Kofler for the initial idea and implementation! See
module I18n
module Backend
module Cascade
def lookup(locale, key, scope = [], options = {})
return super unless cascade = options[:cascade]
cascade = { :step => 1 } unless cascade.is_a?(Hash)
step = cascade[:step] || 1
offset = cascade[:offset] || 1
separator = options[:separator] || I18n.default_separator
skip_root = cascade.has_key?(:skip_root) ? cascade[:skip_root] : true
scope = I18n.normalize_keys(nil, key, scope, separator)
key = (scope.slice!(-offset, offset) || []).join(separator)
result = super
return result unless result.nil?
scope = scope.dup
end while (!scope.empty? || !skip_root) && scope.slice!(-step, step)
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