No longer rely on refinements for Hash utility methods.

Refinements have a very significant performance overhead.
The simple fact of refining a method, even if the refinement
is never used will make calls to that method 40% slower.

On rarely called methods in doesn't matter that much, but I18n
refine some popular Active Support methods, so any project including
the I18n gem suffer from a significant performance penalty.

See this benchmark for more details:
https://gist.github.com/casperisfine/1c46f05cccfa945cd156f445f0d3d6fa

In the end these refinements are easily replace by simple module functions
taking one extra argument.

Gemfile

@@ -7,5 +7,4 @@ gem 'test_declarative', '0.0.6'
 gem 'rake', '~> 13'
 gem 'minitest', '~> 5.14'
 gem 'json'
-gem 'activesupport'
 gem 'pry'

lib/i18n.rb

@@ -4,6 +4,7 @@
 require 'concurrent/hash'
 
 require 'i18n/version'
+require 'i18n/utils'
 require 'i18n/exceptions'
 require 'i18n/interpolate/ruby'
 

lib/i18n/backend/base.rb

@@ -2,12 +2,10 @@
 
 require 'yaml'
 require 'json'
-require 'i18n/core_ext/hash'
 
 module I18n
   module Backend
     module Base
-      using I18n::HashRefinements
       include I18n::Backend::Transliterator
 
       # Accepts a list of paths to translation files. Loads translations from
@@ -53,7 +51,7 @@ def translate(locale, key, options = EMPTY_HASH)
         end
 
         deep_interpolation = options[:deep_interpolation]
-        values = options.except(*RESERVED_KEYS)
+        values = Utils.except(options, *RESERVED_KEYS)
         if values
           entry = if deep_interpolation
             deep_interpolate(locale, entry, values)

lib/i18n/backend/chain.rb

@@ -17,8 +17,6 @@ module Backend
     # The implementation assumes that all backends added to the Chain implement
     # a lookup method with the same API as Simple backend does.
     class Chain
-      using I18n::HashRefinements
-
       module Implementation
         include Base
 
@@ -55,7 +53,7 @@ def available_locales
 
         def translate(locale, key, default_options = EMPTY_HASH)
           namespace = nil
-          options = default_options.except(:default)
+          options = Utils.except(default_options, :default)
 
           backends.each do |backend|
             catch(:exception) do
@@ -101,7 +99,7 @@ def translations
                 init_translations unless initialized?
                 translations
               end
-              memo.deep_merge!(partial_translations) { |_, a, b| b || a }
+              Utils.deep_merge!(memo, partial_translations) { |_, a, b| b || a }
             end
           end
 

lib/i18n/backend/gettext.rb

@@ -31,8 +31,6 @@ module Backend
     # Without it strings containing periods (".") will not be translated.
 
     module Gettext
-      using I18n::HashRefinements
-
       class PoData < Hash
         def set_comment(msgid_or_sym, comment)
           # ignore
@@ -61,7 +59,7 @@ def normalize(locale, data)
                 { part => _normalized.empty? ? value : _normalized }
               end
 
-              result.deep_merge!(normalized)
+              Utils.deep_merge!(result, normalized)
             end
             result
           end

lib/i18n/backend/key_value.rb

@@ -67,8 +67,6 @@ module Backend
     #
     # This is useful if you are using a KeyValue backend chained to a Simple backend.
     class KeyValue
-      using I18n::HashRefinements
-
       module Implementation
         attr_accessor :store
 
@@ -91,7 +89,7 @@ def store_translations(locale, data, options = EMPTY_HASH)
             when Hash
               if @subtrees && (old_value = @store[key])
                 old_value = JSON.decode(old_value)
-                value = old_value.deep_symbolize_keys.deep_merge!(value) if old_value.is_a?(Hash)
+                value = Utils.deep_merge!(Utils.deep_symbolize_keys(old_value), value) if old_value.is_a?(Hash)
               end
             when Proc
               raise "Key-value stores cannot handle procs"
@@ -115,12 +113,12 @@ def available_locales
         # them into a hash such as the one returned from loading the
         # haml files
         def translations
-          @translations = @store.keys.clone.map do |main_key|
+          @translations = Utils.deep_symbolize_keys(@store.keys.clone.map do |main_key|
             main_value = JSON.decode(@store[main_key])
             main_key.to_s.split(".").reverse.inject(main_value) do |value, key|
               {key.to_sym => value}
             end
-          end.inject{|hash, elem| hash.deep_merge!(elem)}.deep_symbolize_keys
+          end.inject{|hash, elem| Utils.deep_merge!(hash, elem)})
         end
 
         def init_translations
@@ -141,7 +139,7 @@ def lookup(locale, key, scope = [], options = EMPTY_HASH)
           value = JSON.decode(value) if value
 
           if value.is_a?(Hash)
-            value.deep_symbolize_keys
+            Utils.deep_symbolize_keys(value)
           elsif !value.nil?
             value
           elsif !@subtrees

lib/i18n/backend/simple.rb

@@ -19,8 +19,6 @@ module Backend
     #
     # I18n::Backend::Simple.include(I18n::Backend::Pluralization)
     class Simple
-      using I18n::HashRefinements
-
       module Implementation
         include Base
 
@@ -40,8 +38,8 @@ def store_translations(locale, data, options = EMPTY_HASH)
           end
           locale = locale.to_sym
           translations[locale] ||= Concurrent::Hash.new
-          data = data.deep_symbolize_keys
-          translations[locale].deep_merge!(data)
+          data = Utils.deep_symbolize_keys(data)
+          Utils.deep_merge!(translations[locale], data)
         end
 
         # Get available locales from the translations hash

lib/i18n/utils.rb

@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+module I18n
+  module Utils
+    class << self
+      if Hash.method_defined?(:except)
+        def except(hash, *keys)
+          hash.except(*keys)
+        end
+      else
+        def except(hash, *keys)
+          hash = hash.dup
+          keys.each { |k| hash.delete(k) }
+          hash
+        end
+      end
+
+      def deep_merge(hash, other_hash, &block)
+        deep_merge!(hash.dup, other_hash, &block)
+      end
+
+      def deep_merge!(hash, other_hash, &block)
+        hash.merge!(other_hash) do |key, this_val, other_val|
+          if this_val.is_a?(Hash) && other_val.is_a?(Hash)
+            deep_merge(this_val, other_val, &block)
+          elsif block_given?
+            yield key, this_val, other_val
+          else
+            other_val
+          end
+        end
+      end
+
+      def deep_symbolize_keys(hash)
+        hash.each_with_object({}) do |(key, value), result|
+          result[key.respond_to?(:to_sym) ? key.to_sym : key] = deep_symbolize_keys_in_object(value)
+          result
+        end
+      end
+
+      private
+
+      def deep_symbolize_keys_in_object(value)
+        case value
+        when Hash
+          deep_symbolize_keys(value)
+        when Array
+          value.map { |e| deep_symbolize_keys_in_object(e) }
+        else
+          value
+        end
+      end
+    end
+  end
+end

test/utils_test.rb

@@ -0,0 +1,30 @@
+require 'test_helper'
+
+class I18nUtilsTest < I18n::TestCase
+
+  test ".deep_symbolize_keys" do
+    hash = { 'foo' => { 'bar' => { 'baz' => 'bar' } } }
+    expected = { :foo => { :bar => { :baz => 'bar' } } }
+    assert_equal expected, I18n::Utils.deep_symbolize_keys(hash)
+  end
+
+  test "#deep_symbolize_keys with numeric keys" do
+    hash = { 1 => { 2 => { 3 => 'bar' } } }
+    expected = { 1 => { 2 => { 3 => 'bar' } } }
+    assert_equal expected, I18n::Utils.deep_symbolize_keys(hash)
+  end
+
+  test "#except" do
+    hash = { :foo => 'bar',  :baz => 'bar' }
+    expected = { :foo => 'bar' }
+    assert_equal expected, I18n::Utils.except(hash, :baz)
+  end
+
+  test "#deep_merge!" do
+    hash = { :foo => { :bar => { :baz => 'bar' } }, :baz => 'bar' }
+    I18n::Utils.deep_merge!(hash, :foo => { :bar => { :baz => 'foo' } })
+
+    expected = { :foo => { :bar => { :baz => 'foo' } }, :baz => 'bar' }
+    assert_equal expected, hash
+  end
+end