From dd888f90eccff9db963865bf138911d1644afc47 Mon Sep 17 00:00:00 2001
From: Evgeny Khramtsov <ekhramtsov@process-one.net>
Date: Mon, 17 Sep 2018 12:08:04 +0300
Subject: [PATCH] Improve error formatting

---
 src/ejabberd_config.erl |  4 ++--
 src/gen_mod.erl         |  9 ++++++---
 src/misc.erl            | 19 ++++++++++++++-----
 3 files changed, 22 insertions(+), 10 deletions(-)

diff --git a/src/ejabberd_config.erl b/src/ejabberd_config.erl
index 6146695c2..d1e7a2f45 100644
--- a/src/ejabberd_config.erl
+++ b/src/ejabberd_config.erl
@@ -1081,12 +1081,12 @@ validate_opts(#state{opts = Opts} = State, ModOpts) ->
 					    ?ERROR_MSG("Invalid value for "
 						       "option '~s' (~s): ~s",
 						       [Opt, Error,
-							misc:format_val(Val)]),
+							misc:format_val({yaml, Val})]),
 					    erlang:error(invalid_option);
 					  _:_ ->
 					    ?ERROR_MSG("Invalid value for "
 						       "option '~s': ~s",
-						       [Opt, misc:format_val(Val)]),
+						       [Opt, misc:format_val({yaml, Val})]),
 					    erlang:error(invalid_option)
 				    end;
 				_ ->
diff --git a/src/gen_mod.erl b/src/gen_mod.erl
index c15b50443..6575e1e82 100644
--- a/src/gen_mod.erl
+++ b/src/gen_mod.erl
@@ -67,7 +67,7 @@
 -type opts() :: [{atom(), any()}].
 -type db_type() :: atom().
 
--callback start(binary(), opts()) -> ok | {ok, pid()}.
+-callback start(binary(), opts()) -> ok | {ok, pid()} | {error, term()}.
 -callback stop(binary()) -> any().
 -callback reload(binary(), opts(), opts()) -> ok | {ok, pid()}.
 -callback mod_opt_type(atom()) -> fun((term()) -> term()) | [atom()].
@@ -548,12 +548,12 @@ validate_opts(Host, Module, Opts0) ->
 	  _:{invalid_option, Opt, Val} ->
 	    ErrTxt = io_lib:format("Invalid value for option '~s' of "
 				   "module ~s: ~s",
-				   [Opt, Module, misc:format_val(Val)]),
+				   [Opt, Module, misc:format_val({yaml, Val})]),
 	    module_error(ErrTxt);
 	  _:{invalid_option, Opt, Val, Reason} ->
 	    ErrTxt = io_lib:format("Invalid value for option '~s' of "
 				   "module ~s (~s): ~s",
-				   [Opt, Module, Reason, misc:format_val(Val)]),
+				   [Opt, Module, Reason, misc:format_val({yaml, Val})]),
 	    module_error(ErrTxt);
 	  _:{unknown_option, Opt, []} ->
 	    ErrTxt = io_lib:format("Unknown option '~s' of module '~s': "
@@ -730,6 +730,9 @@ format_module_error(Module, Fun, Arity, Opts, Class, Reason, St) ->
 			  "it doesn't export ~s/~B callback: "
 			  "is it really an ejabberd module?",
 			  [Fun, Module, Fun, Arity]);
+	{error, {bad_return, Module, {error, _} = Err}} ->
+	    io_lib:format("Failed to ~s module ~s: ~s",
+			  [Fun, Module, misc:format_val(Err)]);
 	{error, {bad_return, Module, Ret}} ->
 	    io_lib:format("Module ~s returned unexpected value from ~s/~B:~n"
                           "** Error: ~p~n"
diff --git a/src/misc.erl b/src/misc.erl
index 5ef71c41b..c415e9817 100644
--- a/src/misc.erl
+++ b/src/misc.erl
@@ -297,15 +297,24 @@ intersection(L1, L2) ->
       end, L1).
 
 -spec format_val(any()) -> iodata().
+format_val({yaml, S}) when is_integer(S); is_binary(S); is_atom(S) ->
+    format_val(S);
+format_val({yaml, YAML}) ->
+    S = try fast_yaml:encode(YAML)
+	catch _:_ -> YAML
+	end,
+    format_val(S);
 format_val(I) when is_integer(I) ->
     integer_to_list(I);
-format_val(S) when is_binary(S) ->
-    <<$", S/binary, $">>;
 format_val(B) when is_atom(B) ->
     erlang:atom_to_binary(B, utf8);
-format_val(YAML) ->
-    try [io_lib:nl(), fast_yaml:encode(YAML)]
-    catch _:_ -> io_lib:format("~p", [YAML])
+format_val(Term) ->
+    S = try iolist_to_binary(Term)
+	catch _:_ -> list_to_binary(io_lib:format("~p", [Term]))
+	end,
+    case binary:match(S, <<"\n">>) of
+	nomatch -> S;
+	_ -> [io_lib:nl(), S]
     end.
 
 -spec cancel_timer(reference()) -> ok.
-- 
2.40.0