Silence warnings for common leaf -> tree expansion scenario.

Closes #242

Signed-off-by: Aleksandrs Ļedovskis <aleksandrs@ledovskis.lv>

lib/i18n/tasks/data/tree/siblings.rb

@@ -100,12 +100,12 @@ def set(full_key, node)
             key: key_part,
             parent: parent,
             children: [],
-            warn_about_add_children_to_leaf: @warn_add_children_to_leaf
+            warn_about_add_children_to_leaf: @warn_about_add_children_to_leaf
           )
           append! child
         end
         unless child.children
-          warn_add_children_to_leaf child if @warn_about_add_children_to_leaf
+          conditionally_warn_add_children_to_leaf(child, [])
           child.children = []
         end
         child.children.set rest, node
@@ -187,7 +187,7 @@ def merge_node!(node, on_leaves_merge: nil) # rubocop:disable Metrics/AbcSize,Me
           if our.children
             our.children.merge!(node.children)
           else
-            warn_add_children_to_leaf our
+            conditionally_warn_add_children_to_leaf(our, node.children)
             our.children = node.children
           end
         elsif on_leaves_merge
@@ -228,6 +228,14 @@ def add_ancestors_that_only_contain_nodes!(nodes)
       end
     end
 
+    def conditionally_warn_add_children_to_leaf(node, children)
+      return unless @warn_about_add_children_to_leaf
+      return if !children.empty? &&
+                (children.map(&:key) - I18n::Tasks::PluralKeys::CLDR_CATEGORY_KEYS).empty?
+
+      warn_add_children_to_leaf(node)
+    end
+
     def warn_add_children_to_leaf(node)
       ::I18n::Tasks::Logging.log_warn "'#{node.full_key}' was a leaf, now has children (value <- scope conflict)"
     end

lib/i18n/tasks/plural_keys.rb

@@ -2,8 +2,10 @@
 
 require 'set'
 module I18n::Tasks::PluralKeys
-  PLURAL_KEY_SUFFIXES = Set.new %w[zero one two few many other]
-  PLURAL_KEY_RE = /\.(?:#{PLURAL_KEY_SUFFIXES.to_a * '|'})$/
+  # Ref: http://cldr.unicode.org/index/cldr-spec/plural-rules
+  CLDR_CATEGORY_KEYS = %w[zero one two few many other].freeze
+  PLURAL_KEY_SUFFIXES = Set.new CLDR_CATEGORY_KEYS
+  PLURAL_KEY_RE = /\.(?:#{CLDR_CATEGORY_KEYS * '|'})$/
 
   def collapse_plural_nodes!(tree)
     tree.leaves.map(&:parent).compact.uniq.each do |node|

spec/locale_tree/siblings_spec.rb

@@ -75,6 +75,14 @@
       a = build_tree(a: 1)
       b = build_tree(a: { b: 1 })
       expect { silence_stderr { a.merge(b) } }.to_not raise_error
+      expect(capture_stderr { a.merge(b) })
+        .to include("[WARN] 'a' was a leaf, now has children (value <- scope conflict)")
+    end
+
+    it '#merge does not warn about conflict with Unicode CLDR category keys' do
+      a = build_tree(a: 1)
+      b = build_tree(a: { zero: 0, one: 1, two: 2, few: 7, many: 88, other: 'ok' })
+      expect(capture_stderr { a.merge(b) }).to be_empty
     end
 
     it '#set conflict value <- scope' do