Warn if we ignore a skip_dir's sub_dirs

src/rebar_subdirs.erl

@@ -38,11 +38,14 @@
 preprocess(Config, _) ->
     %% Get the list of subdirs specified in the config (if any).
     Cwd = rebar_utils:get_cwd(),
-    case rebar_core:is_skip_dir(Cwd) of
-        true ->
+    Subdirs0 = rebar_config:get_local(Config, sub_dirs, []),
+    case {rebar_core:is_skip_dir(Cwd), Subdirs0} of
+        {true, []} ->
             {ok, []};
-        false ->
-            Subdirs0 = rebar_config:get_local(Config, sub_dirs, []),
+        {true, _} ->
+            ?WARN("Ignoring sub_dirs for ~s~n", [Cwd]),
+            {ok, []};
+        {false, _} ->
             Check = check_loop(Cwd),
             ok = lists:foreach(Check, Subdirs0),
             Subdirs = [filename:join(Cwd, Dir) || Dir <- Subdirs0],