add a pterm formatter

src/lager_default_formatter.erl

@@ -98,6 +98,10 @@ 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({pterm, Key}, Msg) ->
+    output({pterm, Key, ""}, Msg);
+output({pterm, Key, Default}, _Msg) ->
+    make_printable(persistent_term:get(Key, Default));
 output(Prop,Msg) when is_atom(Prop) ->
     Metadata = lager_msg:metadata(Msg),
     make_printable(get_metadata(Prop,Metadata,<<"Undefined">>));
@@ -147,6 +151,10 @@ output(metadata, Msg, _Width) ->
 output({metadata, IntSep, FieldSep}, Msg, _Width) ->
     MD = lists:keysort(1, lager_msg:metadata(Msg)),
     [string:join([io_lib:format("~s~s~p", [K, IntSep, V]) || {K, V} <- MD], FieldSep)];
+output({pterm, Key}, Msg, Width) ->
+    output({pterm, Key, ""}, Msg, Width);
+output({pterm, Key, Default}, _Msg, _Width) ->
+    make_printable(persistent_term:get(Key, Default));
 
 output(Prop, Msg, Width) when is_atom(Prop) ->
     Metadata = lager_msg:metadata(Msg),
@@ -505,6 +513,29 @@ basic_test_() ->
                             []),
                         [severity_upper, " Simplist Format"])))
         },
+        {"pterm presence test",
+            ?_assertEqual(<<"Pterm is: something">>,
+              begin
+                persistent_term:put(thing, something),
+                Ret = iolist_to_binary(format(lager_msg:new("Message",
+                            Now,
+                            emergency,
+                            [{pid, self()}],
+                            []),
+                        ["Pterm is: ", {pterm, thing}])),
+                persistent_term:erase(thing),
+                Ret
+              end)
+        },
+        {"pterm absence test",
+            ?_assertEqual(<<"Pterm is: nothing">>,
+                iolist_to_binary(format(lager_msg:new("Message",
+                            Now,
+                            emergency,
+                            [{pid, self()}],
+                            []),
+                        ["Pterm is: ", {pterm, thing, "nothing"}])))
+        },
         {"node formatting basic",
             begin
                 [N, "foo"] = format(lager_msg:new("Message",