From 2a5bf34c20aa6b4051b055fda0d6bab2ab562c06 Mon Sep 17 00:00:00 2001
From: Jeff Kreeftmeijer <jeffkreeftmeijer@gmail.com>
Date: Tue, 25 Apr 2017 15:51:39 +0200
Subject: [PATCH] Function clause errors use their nested stacktraces

---
 lib/appsignal/error_handler.ex                      | 9 +++++++--
 test/appsignal/error_handler/error_matcher_test.exs | 8 ++++++--
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/lib/appsignal/error_handler.ex b/lib/appsignal/error_handler.ex
index e31faf4cd..eaa440d77 100644
--- a/lib/appsignal/error_handler.ex
+++ b/lib/appsignal/error_handler.ex
@@ -78,11 +78,16 @@ defmodule Appsignal.ErrorHandler do
                                     {:pid, pid},
                                     {:registered_name, name},
                                     {:error_info, {_kind, exception, stack}} | _], _linked]) do
-
     msg = "Process #{crash_name(pid, name)} terminating"
+    stacktrace = extract_stacktrace(exception) || stack
     {reason, message} = extract_reason_and_message(exception, msg)
-    {origin, reason, message, Backtrace.from_stacktrace(stack), nil}
+    {origin, reason, message, Backtrace.from_stacktrace(stacktrace), nil}
+  end
+
+  defp extract_stacktrace({_, stacktrace}) when is_list(stacktrace) do
+    stacktrace
   end
+  defp extract_stacktrace(_), do: nil
 
   @doc false
   def format_stack(stacktrace) do
diff --git a/test/appsignal/error_handler/error_matcher_test.exs b/test/appsignal/error_handler/error_matcher_test.exs
index dcb4db427..4730d956a 100644
--- a/test/appsignal/error_handler/error_matcher_test.exs
+++ b/test/appsignal/error_handler/error_matcher_test.exs
@@ -155,7 +155,10 @@ defmodule Appsignal.ErrorHandler.ErrorMatcherTest do
     |> reason(":function_clause")
     |> message(~r(Process #PID<[\d.]+> terminating: {:function_clause...))
     |> stacktrace([
-      "(stdlib) gen_server.erl:812: :gen_server.terminate/7",
+      "(elixir) unicode/unicode.ex:190: String.Unicode.length/1",
+      "test/appsignal/error_handler/error_matcher_test.exs:27: Appsignal.ErrorHandler.ErrorMatcherTest.CrashingGenServer.handle_info/2",
+      "(stdlib) gen_server.erl:601: :gen_server.try_dispatch/4",
+      "(stdlib) gen_server.erl:667: :gen_server.handle_msg/5",
       "(stdlib) proc_lib.erl:247: :proc_lib.init_p_do_apply/3"
     ])
   end
@@ -170,7 +173,8 @@ defmodule Appsignal.ErrorHandler.ErrorMatcherTest do
       ~r(Process #PID<[\d.]+> terminating: {:function_clause, \[{String.Uni...)
     )
     |> stacktrace([
-      "(elixir) lib/task/supervised.ex:116: Task.Supervised.exit/4",
+      "(elixir) unicode/unicode.ex:190: String.Unicode.length/1",
+      "(elixir) lib/task/supervised.ex:85: Task.Supervised.do_apply/2",
       "(stdlib) proc_lib.erl:247: :proc_lib.init_p_do_apply/3"
     ])
   end