Add Logger.levels/0 (#13136)

Co-authored-by: c4710n <[email protected]>

Author: c4710n

lib/logger/lib/logger.ex

@@ -445,6 +445,13 @@ defmodule Logger do
   @levels [:error, :info, :debug] ++ @new_erlang_levels
   @metadata :logger_level
 
+  @doc ~S"""
+  Returns all the available levels.
+  """
+  @doc since: "1.16.0"
+  @spec levels() :: [level(), ...]
+  def levels(), do: @levels
+
   @doc ~S"""
   Returns the default formatter used by Logger.
 

lib/logger/test/logger_test.exs

@@ -16,6 +16,11 @@ defmodule LoggerTest do
     msg("module=LoggerTest #{text}")
   end
 
+  test "levels/0" do
+    assert [_ | _] = Logger.levels()
+    assert :info in Logger.levels()
+  end
+
   test "level/0" do
     assert Logger.level() == :debug