add static analysis rake task for i18n usage

Fixes #5158

rakelib/static.rake

@@ -0,0 +1,32 @@
+require 'rubygems'
+require "bootstrap/environment"
+
+namespace "test" do
+  namespace "static" do
+    desc "run static analysis tests on i18n calls"
+    task "i18n" do
+      require 'i18n'
+
+      locales_path = File.join(LogStash::Environment::LOGSTASH_HOME, "logstash-core", "locales", "en.yml")
+      I18n.enforce_available_locales = true
+      I18n.load_path << locales_path
+      I18n.reload!
+
+      failed = []
+
+      glob_path = File.join(LogStash::Environment::LOGSTASH_HOME, "logstash-*", "**", "*.rb")
+      Dir.glob(glob_path).each do |file_name|
+        File.foreach(file_name) do |line|
+          match = line.match(/I18n.t\("(.+?)"/)
+          next unless match
+          failed << [file_name, match[1]] unless I18n.exists?(match[1])
+        end
+      end
+      if failed.any?
+        message = ["Static Analysis revealed incorrect calls to I18t! See list below:"]
+        failed.each {|file_name, line_match| message << "* #{file_name}: #{line_match}" }
+        raise Exception.new(message.join("\n"))
+      end
+    end
+  end
+end