Adds a rake task to detect missing translations

Rakefile

@@ -20,6 +20,7 @@ load "rails/tasks/engine.rake"
 load "rails/tasks/statistics.rake"
 
 load "lib/tasks/avo_tasks.rake"
+load "lib/tasks/i18n.rake"
 
 require "bundler/gem_tasks"
 

lib/tasks/i18n.rake

@@ -0,0 +1,50 @@
+desc "Compares the en avo translation keys with the other locales and reports missing keys"
+task "avo:i18n:missing_translations" => :environment do
+  # Nothing to compare if there's only one locale
+  return if I18n.available_locales.size <= 1
+
+  # This locale is considered the reference as to what keys should exist
+  locale_to_compare_to = :en
+
+  # Ensure translations are loaded
+  I18n.backend.send(:init_translations)
+
+  # Get all translations
+  translations = I18n.backend.send(:translations)
+
+  # Helper method to collect all translation keys in in a given scope
+  def collect_translation_keys(scope, translations)
+    translations.map do |key, translations|
+      new_scope = scope + [key]
+      if translations.is_a?(Hash)
+        collect_translation_keys(new_scope, translations)
+      else
+        new_scope.join(".")
+      end
+    end.flatten
+  end
+
+  # Collect all avo translation keys in the reference locale
+  reference_keys = collect_translation_keys([], translations[locale_to_compare_to][:avo]).freeze
+
+  locales_with_missing_keys = {}
+
+  I18n.available_locales.without(locale_to_compare_to).reject do |locale|
+    # Skip locales that don't contain avo translations
+    translations[locale][:avo].nil?
+  end.each do |locale|
+    locale_keys = collect_translation_keys([], translations[locale][:avo])
+
+    missing_keys = reference_keys - locale_keys
+
+    locales_with_missing_keys[locale] = missing_keys if missing_keys.any?
+  end
+
+  locales_with_missing_keys.each do |locale, missing_keys|
+    puts "Missing keys in #{locale}:"
+    puts missing_keys.map { |k| "  #{locale}.avo.#{k}" }.join("\n")
+  end
+
+  # Signal an error if any missing keys were found (for CI)
+  exit 1 if locales_with_missing_keys.any?
+end