From 12d2a6f5c6a00ffd6907ca09811e5695d75c024c Mon Sep 17 00:00:00 2001
From: Andrew Thompson <andrew@hijacked.us>
Date: Sun, 31 Dec 2017 11:52:50 -0800
Subject: [PATCH] Handle yet another stacktrace form

Sometimes the stacktrace is a larger array of {M, F, A, Prop} tuples.
The handler code was expecting at most 2 tuples in the list. Relax this
requirement and add a test that provokes this edge-case.
---
 src/error_logger_lager_h.erl | 8 +++++---
 test/crash.erl               | 3 +++
 test/lager_test_backend.erl  | 1 +
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/src/error_logger_lager_h.erl b/src/error_logger_lager_h.erl
index 6866496..af0afa1 100644
--- a/src/error_logger_lager_h.erl
+++ b/src/error_logger_lager_h.erl
@@ -500,7 +500,7 @@ format_reason_md({{badarity, {Fun, Args}}, [MFA|_]}) ->
                     [length(Args), Arity]), Formatted]};
 format_reason_md({noproc, MFA}) ->
     {Md, Formatted} = format_mfa_md(MFA),
-    {[{reason, badarity} | Md],
+    {[{reason, noproc} | Md],
      ["no such process or port in call to ", Formatted]};
 format_reason_md({{badfun, Term}, [MFA|_]}) ->
     {Md, Formatted} = format_mfa_md(MFA),
@@ -537,11 +537,13 @@ format_mfa_md({M, F, A, Props}) when is_list(Props) ->
             {Md, Formatted} = format_mfa_md({M, F, A}),
             {[{line, Line} | Md], [Formatted, io_lib:format(" line ~w", [Line])]}
     end;
-format_mfa_md([{M, F, A}, _]) ->
+format_mfa_md([{M, F, A}| _]) ->
    %% this kind of weird stacktrace can be generated by a uncaught throw in a gen_server
    format_mfa_md({M, F, A});
-format_mfa_md([{M, F, A, Props}, _]) when is_list(Props) ->
+format_mfa_md([{M, F, A, Props}| _]) when is_list(Props) ->
    %% this kind of weird stacktrace can be generated by a uncaught throw in a gen_server
+   %% TODO we might not always want to print the first MFA we see here, often it is more helpful
+   %% to print a lower one, but it is hard to programatically decide.
    format_mfa_md({M, F, A, Props});
 format_mfa_md(Other) ->
     {[], io_lib:format("~w", [Other])}.
diff --git a/test/crash.erl b/test/crash.erl
index bb871c9..560b17e 100644
--- a/test/crash.erl
+++ b/test/crash.erl
@@ -81,6 +81,9 @@ handle_call(port_limit, _, State) ->
 handle_call(noproc, _, State) ->
     Res = gen_event:call(foo, bar, baz),
     {reply, Res, State};
+handle_call(noproc_proc_lib, _, State) ->
+    Res = proc_lib:stop(foo),
+    {reply, Res, State};
 handle_call(badarity, _, State) ->
     F = fun(A, B, C) -> A + B + C end,
     Res = F(State),
diff --git a/test/lager_test_backend.erl b/test/lager_test_backend.erl
index a055c4e..fb7dd80 100644
--- a/test/lager_test_backend.erl
+++ b/test/lager_test_backend.erl
@@ -1107,6 +1107,7 @@ error_logger_redirect_crash_test_() ->
         TestBody("bad arg2",badarg2,"gen_server crash terminated with reason: bad argument in call to erlang:iolist_to_binary([\"foo\",bar]) in crash:handle_call/3"),
         TestBody("bad record",badrecord,"gen_server crash terminated with reason: bad record state in crash:handle_call/3"),
         TestBody("noproc",noproc,"gen_server crash terminated with reason: no such process or port in call to gen_event:call(foo, bar, baz)"),
+        TestBody("noproc_proc_lib",noproc_proc_lib,"gen_server crash terminated with reason: no such process or port in call to proc_lib:stop/3"),
         TestBody("badfun",badfun,"gen_server crash terminated with reason: bad function booger in crash:handle_call/3")
     ],
     {"Error logger redirect crash", [