Fixed issue 1 "priv/mibs/ is not automatically created"

src/rebar_erlc_compiler.erl

@@ -149,7 +149,8 @@ internal_erl_compile(Source, Config, Outdir) ->
             skipped
     end.
 
-compile_mib(Source, _Target, Config) ->
+compile_mib(Source, Target, Config) ->
+    ok = rebar_utils:ensure_dir(Target),
     Opts = [{outdir, "priv/mibs"}, {i, ["priv/mibs"]}] ++
         rebar_config:get(Config, mib_opts, []),
     case snmpc:compile(Source, Opts) of

src/rebar_utils.erl

@@ -32,7 +32,8 @@
          sh/2, sh/3,
          sh_failfast/2,
          find_files/2,
-         now_str/0]).
+         now_str/0,
+         ensure_dir/1]).
 
 -include("rebar.hrl").
 
@@ -89,6 +90,24 @@ now_str() ->
     lists:flatten(io_lib:format("~4b/~2..0b/~2..0b ~2..0b:~2..0b:~2..0b", 
 				[Year, Month, Day, Hour, Minute, Second])).
 
+%% TODO: Review why filelib:ensure_dir/1 sometimes returns {error, eexist}.
+%% There appears to be a race condition when calling ensure_dir from
+%% multiple processes simultaneously.
+%% This does not happen with -j1 but with anything higher than that.
+%% So -j2 or default jobs setting will reveal the issue.
+%% To reproduce make sure that the priv/mibs directory does not exist
+%% $ rm -r priv
+%% $ ./rebar -v compile
+ensure_dir(Path) ->
+    case filelib:ensure_dir(Path) of
+        ok ->
+            ok;
+        {error,eexist} ->
+            ok;
+        Error ->
+            Error
+    end.
+
 %% ====================================================================
 %% Internal functions
 %% ====================================================================