It turns out that a deep merge isn’t required, #3474

All locale files are a top-level locale key with a Hash of (key, string) translations, nothing more iirc.

lib/sidekiq/core_ext.rb

@@ -76,7 +76,6 @@ end
 
 begin
   require 'active_support/core_ext/hash/keys'
-  require 'active_support/core_ext/hash/deep_merge'
 rescue LoadError
   class Hash
     def stringify_keys
@@ -93,21 +92,6 @@ rescue LoadError
       self
     end if !{}.respond_to?(:symbolize_keys)
 
-    def deep_merge(other_hash, &block)
-      dup.deep_merge!(other_hash, &block)
-    end if !{}.respond_to?(:deep_merge)
-
-    def deep_merge!(other_hash, &block)
-      other_hash.each_pair do |k,v|
-        tv = self[k]
-        if tv.is_a?(Hash) && v.is_a?(Hash)
-          self[k] = tv.deep_merge(v, &block)
-        else
-          self[k] = block && tv ? block.call(k, tv, v) : v
-        end
-      end
-      self
-    end if !{}.respond_to?(:deep_merge!)
   end
 end
 

lib/sidekiq/web/helpers.rb

@@ -15,7 +15,7 @@ module Sidekiq
         settings.locales.each_with_object({}) do |path, global|
           find_locale_files(lang).each do |file|
             strs = YAML.load(File.open(file))
-            global.deep_merge!(strs[lang])
+            global.merge!(strs[lang])
           end
         end
       end