Get closer to full CLDR pluralization support

lib/i18n/backend/pluralization.rb

@@ -16,40 +16,81 @@ module Backend
  module Pluralization
  # Overwrites the Base backend translate method so that it will check the
  # translation meta data space (:i18n) for a locale specific pluralization
- # rule and use it to pluralize the given entry. I.e. the library expects
+ # rule and use it to pluralize the given entry. I.e., the library expects
  # pluralization rules to be stored at I18n.t(:'i18n.plural.rule')
  #
  # Pluralization rules are expected to respond to #call(count) and
- # return a pluralization key. Valid keys depend on the translation data
- # hash (entry) but it is generally recommended to follow CLDR's style,
- # i.e., return one of the keys :zero, :one, :few, :many, :other.
+ # return a pluralization key. Valid keys depend on the pluralization
+ # rules for the locale, as defined in the CLDR.
+ # As of v41, 6 locale-specific plural categories are defined:
+ # :few, :many, :one, :other, :two, :zero
  #
- # The :zero key is always picked directly when count equals 0 AND the
- # translation data has the key :zero. This way translators are free to
- # either pick a special :zero translation even for languages where the
- # pluralizer does not return a :zero key.
+ # n.b., The :one plural category does not imply the number 1.
+ # Instead, :one is a category for any number that behaves like 1 in
+ # that locale. For example, in some locales, :one is used for numbers
+ # that end in "1" (like 1, 21, 151) but that don't end in
+ # 11 (like 11, 111, 10311).
+ # Similar notes apply to the :two, and :zero plural categories.
+ #
+ # If you want to have different strings for the categories of count == 0
+ # (e.g. "I don't have any cars") or count == 1 (e.g. "I have a single car")
+ # use the explicit `"0"` and `"1"` keys.
+ # https://unicode-org.github.io/cldr/ldml/tr35-numbers.html#Explicit_0_1_rules
  def pluralize(locale, entry, count)
  return entry unless entry.is_a?(Hash) && count
 
  pluralizer = pluralizer(locale)
  if pluralizer.respond_to?(:call)
- key = count == 0 && entry.has_key?(:zero) ? :zero : pluralizer.call(count)
- raise InvalidPluralizationData.new(entry, count, key) unless entry.has_key?(key)
- entry[key]
+ # Deprecation: The use of the `zero` key in this way is incorrect.
+ # Users that want a different string for the case of `count == 0` should use the explicit "0" key instead.
+ # We keep this incorrect behaviour for now for backwards compatibility until we can remove it.
+ # Ref: https:/ruby-i18n/i18n/issues/629
+ return entry[:zero] if count == 0 && entry.has_key?(:zero)
+
+ # "0" and "1" are special cases
+ # https://unicode-org.github.io/cldr/ldml/tr35-numbers.html#Explicit_0_1_rules
+ if count == 0 || count == 1
+ value = entry[symbolic_count(count)]
+ return value if value
+ end
+
+ # Lateral Inheritance of "count" attribute (http://www.unicode.org/reports/tr35/#Lateral_Inheritance):
+ # > If there is no value for a path, and that path has a [@count="x"] attribute and value, then:
+ # > 1. If "x" is numeric, the path falls back to the path with [@count=«the plural rules category for x for that locale»], within that the same locale.
+ # > 2. If "x" is anything but "other", it falls back to a path [@count="other"], within that the same locale.
+ # > 3. If "x" is "other", it falls back to the path that is completely missing the count item, within that the same locale.
+ # Note: We don't yet implement #3 above, since we haven't decided how lateral inheritance attributes should be represented.
+ plural_rule_category = pluralizer.call(count)
+
+ value = if entry.has_key?(plural_rule_category) || entry.has_key?(:other)
+ entry[plural_rule_category] || entry[:other]
+ else
+ raise InvalidPluralizationData.new(entry, count, plural_rule_category)
+ end
  else
  super
  end
  end
 
  protected
 
-  def pluralizers
-  @pluralizers ||= {}
-  end
+ def pluralizers
+ @pluralizers ||= {}
+ end
 
- def pluralizer(locale)
- pluralizers[locale] ||= I18n.t(:'i18n.plural.rule', :locale => locale, :resolve => false)
- end
+ def pluralizer(locale)
+ pluralizers[locale] ||= I18n.t(:'i18n.plural.rule', :locale => locale, :resolve => false)
+ end
+
+ private
+
+ # Normalizes categories of 0.0 and 1.0
+ # and returns the symbolic version
+ def symbolic_count(count)
+ count = 0 if count == 0
+ count = 1 if count == 1
+ count.to_s.to_sym
+ end
  end
  end
 end

test/backend/pluralization_test.rb

@@ -9,16 +9,23 @@ class Backend < I18n::Backend::Simple
  def setup
  super
  I18n.backend = Backend.new
- @rule = lambda { |n| n == 1 ? :one : n == 0 || (2..10).include?(n % 100) ? :few : (11..19).include?(n % 100) ? :many : :other }
+ @rule = lambda { |n| n % 10 == 1 && n % 100 != 11 ? :one : n == 0 || (2..10).include?(n % 100) ? :few : (11..19).include?(n % 100) ? :many : :other }
  store_translations(:xx, :i18n => { :plural => { :rule => @rule } })
- @entry = { :zero => 'zero', :one => 'one', :few => 'few', :many => 'many', :other => 'other' }
+ @entry = { :"0" => 'none', :"1" => 'single', :one => 'one', :few => 'few', :many => 'many', :other => 'other' }
+ @entry_with_zero = @entry.merge( { :zero => 'zero' } )
  end
 
  test "pluralization picks a pluralizer from :'i18n.pluralize'" do
  assert_equal @rule, I18n.backend.send(:pluralizer, :xx)
  end
 
- test "pluralization picks :one for 1" do
+ test "pluralization picks the explicit 1 rule for count == 1, the explicit rule takes priority over the matching :one rule" do
+ assert_equal 'single', I18n.t(:count => 1, :default => @entry, :locale => :xx)
+ assert_equal 'single', I18n.t(:count => 1.0, :default => @entry, :locale => :xx)
+ end
+
+ test "pluralization picks :one for 1, since in this case that is the matching rule for 1 (when there is no explicit 1 rule)" do
+ @entry.delete(:"1")
  assert_equal 'one', I18n.t(:count => 1, :default => @entry, :locale => :xx)
  end
 
@@ -31,14 +38,25 @@ def setup
  end
 
  test "pluralization picks zero for 0 if the key is contained in the data" do
- assert_equal 'zero', I18n.t(:count => 0, :default => @entry, :locale => :xx)
+ assert_equal 'zero', I18n.t(:count => 0, :default => @entry_with_zero, :locale => :xx)
+ end
+
+ test "pluralization picks explicit 0 rule for count == 0, since the explicit rule takes priority over the matching :few rule" do
+ assert_equal 'none', I18n.t(:count => 0, :default => @entry, :locale => :xx)
+ assert_equal 'none', I18n.t(:count => 0.0, :default => @entry, :locale => :xx)
+ assert_equal 'none', I18n.t(:count => -0, :default => @entry, :locale => :xx)
  end
 
- test "pluralization picks few for 0 if the key is not contained in the data" do
- @entry.delete(:zero)
+ test "pluralization picks :few for 0 (when there is no explicit 0 rule)" do
+ @entry.delete(:"0")
  assert_equal 'few', I18n.t(:count => 0, :default => @entry, :locale => :xx)
  end
 
+ test "pluralization does Lateral Inheritance to :other to cover missing data" do
+ @entry.delete(:many)
+ assert_equal 'other', I18n.t(:count => 11, :default => @entry, :locale => :xx)
+ end
+
  test "pluralization picks one for 1 if the entry has attributes hash on unknown locale" do
  @entry[:attributes] = { :field => 'field', :second => 'second' }
  assert_equal 'one', I18n.t(:count => 1, :default => @entry, :locale => :pirate)