Ensure translators are persisted across logger restarts

Author: josevalim

lib/logger/lib/logger.ex

@@ -878,9 +878,12 @@ defmodule Logger do
 
   defp update_translators(updater) do
     :elixir_config.serial(fn ->
+      translators = updater.(Application.fetch_env!(:logger, :translators))
+      Application.put_env(:logger, :translators, translators)
+
       with %{filters: filters} <- :logger.get_primary_config(),
            {{_, {fun, config}}, filters} <- List.keytake(filters, :logger_translator, 0) do
-        config = update_in(config.translators, updater)
+        config = %{config | translators: translators}
         :ok = :logger.set_primary_config(:filters, filters ++ [logger_translator: {fun, config}])
       end
     end)

lib/logger/test/logger/backends/handler_test.exs

@@ -58,7 +58,9 @@ defmodule Logger.Backends.HandlerTest do
   end
 
   test "add_translator/1 and remove_translator/1 for logger formats" do
+    refute {CustomTranslator, :t} in Application.fetch_env!(:logger, :translators)
     assert Logger.add_translator({CustomTranslator, :t})
+    assert {CustomTranslator, :t} in Application.fetch_env!(:logger, :translators)
 
     assert capture_log(fn ->
              :logger.info(~c"hello: ~p", [:ok])