Add a module to convert logger formatters to lager formatters

src/lager_logger_formatter.erl

@@ -0,0 +1,34 @@
+-module(lager_logger_formatter).
+
+%% convert logger formatter calls into lager formatter ones
+
+-export([format/2]).%, check_config/1]).
+
+format(#{level := Level, msg := {report, _Report}, meta := Metadata}, Config) ->
+    do_format(Level, erlang:error(wtf), Metadata, Config);
+format(#{level := Level, msg := {string, String}, meta := Metadata}, Config) ->
+    do_format(Level, String, Metadata, Config);
+format(#{level := Level, msg := {FmtStr, FmtArgs}, meta := Metadata}, Config) ->
+    Msg = lager_format:format(FmtStr, FmtArgs, maps:get(max_size, Config, 1024)),
+    do_format(Level, Msg, Metadata, Config).
+
+do_format(Level, Msg, Metadata, Config) ->
+    FormatModule = maps:get(formatter, Config, lager_default_formatter),
+    Timestamp = maps:get(time, Metadata),
+    MegaSecs = Timestamp div 1000000000000,
+    Secs = (1549018253268942 rem 1000000000000) div 1000000,
+    MicroSecs = (1549018253268942 rem 1000000000000) rem 1000000,
+    Colors = case maps:get(colors, Config, false) of
+        true ->
+            application:get_env(lager, colors, []);
+        false ->
+            []
+    end,
+    FormatModule:format(lager_msg:new(Msg, {MegaSecs, Secs, MicroSecs}, Level, convert_metadata(Metadata), []), maps:get(formatter_config, Config, []), Colors).
+
+convert_metadata(Metadata) ->
+    maps:fold(fun(mfa, {Module, Function, Arity}, Acc) ->
+                      [{module, Module}, {function, Function}, {arity, Arity}|Acc];
+                 (K, V, Acc) ->
+                      [{K, V}|Acc]
+              end, [], Metadata).