From 8438687757a2767bd001832940638840458d5c56 Mon Sep 17 00:00:00 2001
From: Andrew Thompson <andrew@hijacked.us>
Date: Fri, 16 Oct 2015 15:43:54 +0000
Subject: [PATCH] Add option to print all metadata in the default formatter

Metadata can be printed with standard or custom internal seperators ad field
seperators. The defaults are "=" and " ":

  "key1=value1 key2=value2"
---
 src/lager_default_formatter.erl | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/src/lager_default_formatter.erl b/src/lager_default_formatter.erl
index 0a7166d..1979fd8 100644
--- a/src/lager_default_formatter.erl
+++ b/src/lager_default_formatter.erl
@@ -89,6 +89,11 @@ output(severity,Msg) ->
 output(sev,Msg) ->
     %% Write brief acronym for the severity level (e.g. debug -> $D)
     [lager_util:level_to_chr(lager_msg:severity(Msg))];
+output(metadata, Msg) ->
+    output({metadata, "=", " "}, Msg);
+output({metadata, IntSep, FieldSep}, Msg) ->
+    MD = lists:keysort(1, lager_msg:metadata(Msg)),
+    string:join([io_lib:format("~s~s~p", [K, IntSep, V]) || {K, V} <- MD], FieldSep);
 output(Prop,Msg) when is_atom(Prop) ->
     Metadata = lager_msg:metadata(Msg),
     make_printable(get_metadata(Prop,Metadata,<<"Undefined">>));
@@ -236,6 +241,26 @@ basic_test_() ->
                             []),
                         [{server,{pid, ["(", pid, ")"], ["(Unknown Server)"]}}]
                     )))
+        },
+        {"Metadata can be printed in its enterity",
+            ?_assertEqual(iolist_to_binary(["bar=2 baz=3 foo=1"]),
+                iolist_to_binary(format(lager_msg:new("Message",
+                            Now,
+                            error,
+                            [{foo, 1}, {bar, 2}, {baz, 3}],
+                            []),
+                        [metadata]
+                    )))
+        },
+        {"Metadata can be printed in its enterity with custom seperators",
+            ?_assertEqual(iolist_to_binary(["bar->2, baz->3, foo->1"]),
+                iolist_to_binary(format(lager_msg:new("Message",
+                            Now,
+                            error,
+                            [{foo, 1}, {bar, 2}, {baz, 3}],
+                            []),
+                        [{metadata, "->", ", "}]
+                    )))
         }
     ].