Handle :function metadata properly, closes #12703

Author: josevalim

lib/logger/lib/logger/formatter.ex

@@ -203,7 +203,7 @@ defmodule Logger.Formatter do
 
   def format(_event, _config) do
     raise "invalid configuration for Logger.Formatter. " <>
-            "Use Logger.Formatter.init/1 to define a formatter"
+            "Use Logger.Formatter.new/1 to define a formatter"
   end
 
   defp compute_meta(:module, %{mfa: {mod, _, _}}), do: mod
@@ -498,8 +498,6 @@ defmodule Logger.Formatter do
     rest
   end
 
-  defp metadata(:file, file) when is_list(file), do: file
-
   defp metadata(:domain, [head | tail]) when is_atom(head) do
     Enum.map_intersperse([head | tail], ?., &Atom.to_string/1)
   end
@@ -514,6 +512,8 @@ defmodule Logger.Formatter do
     Exception.format_mfa(mod, fun, arity)
   end
 
+  defp metadata(:function, function) when is_list(function), do: function
+  defp metadata(:file, file) when is_list(file), do: file
   defp metadata(_, list) when is_list(list), do: nil
 
   defp metadata(_, other) do

lib/logger/test/logger/formatter_test.exs

@@ -54,6 +54,28 @@ defmodule Logger.FormatterTest do
     assert format_time(time) == ["12", ?:, "30", ?:, "10", ?., [?0, "10"]]
   end
 
+  describe "log" do
+    test "handles :module and :function" do
+      {_, formatter} =
+        new(
+          format: "\n$time $metadata[$level] $message\n",
+          metadata: [:module, :function, :mfa],
+          colors: [enabled: false]
+        )
+
+      assert %{
+               level: :warn,
+               msg: {:string, "foo"},
+               meta: %{
+                 mfa: {Logger.Formatter, :compile, 1}
+               }
+             }
+             |> format(formatter)
+             |> IO.chardata_to_string() =~
+               "module=Logger.Formatter function=compile/1 mfa=Logger.Formatter.compile/1"
+    end
+  end
+
   describe "compile + format" do
     defmodule CompileMod do
       def format(_level, _msg, _ts, _md) do
@@ -66,7 +88,7 @@ defmodule Logger.FormatterTest do
                ["\n", :time, " ", :metadata, "[", :level, "] ", :message, "\n"]
     end
 
-    test "compile with str" do
+    test "compile with string" do
       assert compile("$level $time $date $metadata $message $node") ==
                Enum.intersperse([:level, :time, :date, :metadata, :message, :node], " ")