Do not consider handler swap to be failures

Author: José Valim

lib/elixir/lib/gen_event.ex

@@ -885,13 +885,13 @@ defmodule GenEvent do
 
     receive do
       {^ref, :ok} ->
-        server_collect_process_handlers(:sync, event, t, [handler|handlers], name)
+        server_collect_process_handlers(mode, event, t, [handler|handlers], name)
       {^ref, :done} ->
         do_terminate(handler, :remove_handler, event, name, :normal)
-        server_collect_process_handlers(:sync, event, t, handlers, name)
+        server_collect_process_handlers(mode, event, t, handlers, name)
       {:DOWN, ^ref, _, _, reason} ->
         do_terminate(handler, {:stop, reason}, :remove, name, :shutdown)
-        server_collect_process_handlers(:sync, event, t, handlers, name)
+        server_collect_process_handlers(mode, event, t, handlers, name)
     end
   end
 

lib/elixir/lib/gen_event/stream.ex

@@ -159,12 +159,9 @@ defimpl Enumerable, for: GenEvent.Stream do
       {_from, {^pid, ^ref}, {notify, _event}} when notify in [:ack_notify, :sync_notify] ->
         send pid, {ref, :done}
         wait_for_handler_removal(pid, ref, mon_ref)
-      {:gen_event_EXIT, {GenEvent.Stream, ^ref}, reason} when reason in [:normal, :shutdown] ->
+      {:gen_event_EXIT, {GenEvent.Stream, ^ref}, _reason} ->
         Process.demonitor(mon_ref, [:flush])
         :ok
-      {:gen_event_EXIT, {GenEvent.Stream, ^ref}, reason} ->
-        Process.demonitor(mon_ref, [:flush])
-        {:error, reason}
       {:DOWN, ^mon_ref, _, _, reason} ->
         {:error, reason}
     end

lib/elixir/test/elixir/gen_event/stream_test.exs

@@ -214,19 +214,16 @@ defmodule GenEvent.StreamTest do
       stream = GenEvent.stream(pid, id: make_ref())
 
       parent = self()
-      child = spawn_link fn -> send parent, Enum.take(stream, 5) end
+      spawn_link(fn -> send parent, Enum.take(stream, 5) end)
       wait_for_handlers(pid, 1)
 
       for i <- 1..3 do
         notify(@mode, pid, i)
       end
 
       [handler] = GenEvent.which_handlers(pid)
-      Process.flag(:trap_exit, true)
       GenEvent.swap_handler(pid, handler, :swap_handler, UnknownHandler, [])
-      assert_receive {:EXIT, ^child,
-                       {{:swapped, UnknownHandler, _},
-                        {Enumerable.GenEvent.Stream, :stop, [_, _]}}}, @receive_timeout
+      assert_receive [1, 2, 3], @receive_timeout
     end
 
     test "#{mode} stream/2 with manager unregistered" do