From b7da929f69f900c7f10255f82a39f562799bd087 Mon Sep 17 00:00:00 2001
From: MaximMinin <maxim.minin@gmx.de>
Date: Wed, 15 Apr 2015 14:58:57 +0200
Subject: [PATCH 1/2] trace_file don't work, if env "log_root" is set.

---
 src/lager.erl | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/lager.erl b/src/lager.erl
index cfae17d..f617b0a 100644
--- a/src/lager.erl
+++ b/src/lager.erl
@@ -150,24 +150,25 @@ trace_file(File, Filter, Options) when is_list(Options) ->
     trace_file(File, Filter, debug, Options).
 
 trace_file(File, Filter, Level, Options) ->
-    Trace0 = {Filter, Level, {lager_file_backend, File}},
+    FileName = lager_util:expand_path(File),
+    Trace0 = {Filter, Level, {lager_file_backend, FileName}},
     case lager_util:validate_trace(Trace0) of
         {ok, Trace} ->
             Handlers = gen_event:which_handlers(lager_event),
             %% check if this file backend is already installed
-            Res = case lists:member({lager_file_backend, File}, Handlers) of
+            Res = case lists:member({lager_file_backend, FileName}, Handlers) of
                false ->
                      %% install the handler
-                    LogFileConfig = lists:keystore(level, 1, lists:keystore(file, 1, Options, {file, File}), {level, none}),
+                    LogFileConfig = lists:keystore(level, 1, lists:keystore(file, 1, Options, {file, FileName}), {level, none}),
                     supervisor:start_child(lager_handler_watcher_sup,
-                        [lager_event, {lager_file_backend, File}, LogFileConfig]);
+                        [lager_event, {lager_file_backend, FileName}, LogFileConfig]);
                 _ ->
                     {ok, exists}
             end,
             case Res of
               {ok, _} ->
                 add_trace_to_loglevel_config(Trace),
-                {ok, {{lager_file_backend, File}, Filter, Level}};
+                {ok, {{lager_file_backend, FileName}, Filter, Level}};
               {error, _} = E ->
                 E
             end;

From d66790f6124ef227e15e962fa89068d639032df4 Mon Sep 17 00:00:00 2001
From: MaximMinin <maxim.minin@gmx.de>
Date: Thu, 23 Apr 2015 18:00:28 +0200
Subject: [PATCH 2/2] test for tracing to a dedicated file if root_log is set.

---
 src/lager_file_backend.erl | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/lager_file_backend.erl b/src/lager_file_backend.erl
index f5ab2c9..87c69e2 100644
--- a/src/lager_file_backend.erl
+++ b/src/lager_file_backend.erl
@@ -708,6 +708,20 @@ filesystem_test_() ->
                         ?assertMatch([_, _, "[error]", _, "Test message\n"], re:split(Bin3, " ", [{return, list}, {parts, 5}]))
                 end
             },
+            {"tracing to a dedicated file should work even if root_log is set",
+                fun() ->
+                        {ok, P} = file:get_cwd(),
+                        file:delete(P ++ "/test_root_log/foo.log"),
+                        application:set_env(lager, log_root, P++"/test_root_log"),
+                        {ok, _} = lager:trace_file("foo.log", [{module, ?MODULE}]),
+                        lager:error("Test message"),
+                        %% not elegible for trace
+                        lager:log(error, self(), "Test message"),
+                        {ok, Bin3} = file:read_file(P++"/test_root_log/foo.log"),
+                        application:unset_env(lager, log_root),
+                        ?assertMatch([_, _, "[error]", _, "Test message\n"], re:split(Bin3, " ", [{return, list}, {parts, 5}]))
+                end
+            },
             {"tracing with options should work",
                 fun() ->
                         file:delete("foo.log"),