Fallback when logging isn't initialized

In some cases, such as when the global rebar.config file contains typoes
and invalid terms, the rebar3 executable fails when trying to log the
error since it hasn't been set yet, such as in #1792

This patch fixes that by going for a fallback mechanism.

1 files changed, 11 insertions, 4 deletions

diff --git a/src/rebar_log.erl b/src/rebar_log.erl
index 9150346..7fc2312 100644
--- a/src/rebar_log.erl
+++ b/src/rebar_log.erl
@@ -93,11 +93,18 @@ get_level() ->
     end.
 
 log(Level = error, Str, Args) ->
-    {ok, LogState} = application:get_env(rebar, log),
-    ec_cmd_log:Level(LogState, lists:flatten(cf:format("~!^~ts~n", [Str])), Args);
+    case application:get_env(rebar, log) of
+        {ok, LogState} ->
+            NewStr = lists:flatten(cf:format("~!^~ts~n", [Str])),
+            ec_cmd_log:Level( LogState, NewStr, Args);
+        undefined -> % fallback
+            io:format(standard_error, Str++"~n", Args)
+    end;
 log(Level, Str, Args) ->
-    {ok, LogState} = application:get_env(rebar, log),
-    ec_cmd_log:Level(LogState, Str++"~n", Args).
+    case application:get_env(rebar, log) of
+        {ok, LogState} -> ec_cmd_log:Level(LogState, Str++"~n", Args);
+        undefined -> io:format(Str++"~n", Args)
+    end.
 
 crashdump(Str, Args) ->
     crashdump("rebar3.crashdump", Str, Args).