Better crash reports for processes started via proc_lib, Fixes erlang…

…-lager#31

src/error_logger_lager_h.erl

@@ -159,9 +159,15 @@ format_crash_report(Report, Neighbours) ->
             proplists:get_value(pid, Report);
         Atom -> Atom
     end,
-    {_Class, Reason, _Trace} = proplists:get_value(error_info, Report),
+    {_Class, Reason, Trace} = proplists:get_value(error_info, Report),
+    ReasonStr = case is_atom(Reason) of
+        true ->
+            format_reason({Reason, Trace});
+        _ ->
+            format_reason(Reason)
+    end,
     io_lib:format("Process ~w with ~w neighbours crashed with reason: ~s",
-        [Name, length(Neighbours), format_reason(Reason)]).
+        [Name, length(Neighbours), ReasonStr]).
 
 format_offender(Off) ->
     case proplists:get_value(mfargs, Off) of

test/lager_test_backend.erl

@@ -685,6 +685,19 @@ error_logger_redirect_test_() ->
                         ?assert(length(lists:flatten(Msg)) < 650)
                 end
             },
+            {"crash reports for 'special processes' should be handled right", 
+                fun() ->
+                        {ok, Pid} = special_process:start(),
+                        unlink(Pid),
+                        Pid ! function_clause,
+                        timer:sleep(500),
+                        _ = gen_event:which_handlers(error_logger),
+                        {_, _, Msg} = pop(),
+                        Expected = lists:flatten(io_lib:format("[error] ~p CRASH REPORT Process ~p with 0 neighbours crashed with reason: no function clause matching special_process:foo(bar)",
+                                [Pid, Pid])),
+                        ?assertEqual(Expected, lists:flatten(Msg))
+                end
+            },
             {"messages should not be generated if they don't satisfy the threshold",
                 fun() ->
                         lager:set_loglevel(?MODULE, error),

test/special_process.erl

@@ -0,0 +1,28 @@
+-module(special_process).
+-export([start/0, init/1]).
+
+start() ->
+    proc_lib:start_link(?MODULE, init, [self()]).
+
+init(Parent) ->
+    proc_lib:init_ack(Parent, {ok, self()}),
+    loop().
+
+loop() ->
+    receive
+        function_clause ->
+            foo(bar),
+            loop();
+        exit ->
+            exit(byebye),
+            loop();
+        error ->
+            erlang:error(mybad),
+            loop();
+        _ ->
+            loop()
+    end.
+
+foo(baz) ->
+    ok.
+