From 071599cbcd25cd2669e26d23a6e202e0275f191a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lo=C3=AFc=20Hoguin?= <essen@ninenines.eu>
Date: Wed, 3 Jul 2019 17:22:43 +0200
Subject: Add the response_trailers event

---
 src/gun_default_event_h.erl |  4 ++++
 src/gun_event.erl           | 11 ++++++++++-
 src/gun_http.erl            |  6 ++++--
 src/gun_http2.erl           | 11 +++++------
 test/event_SUITE.erl        | 19 ++++++++++++++++++-
 5 files changed, 41 insertions(+), 10 deletions(-)

diff --git a/src/gun_default_event_h.erl b/src/gun_default_event_h.erl
index cd48fc2..ff6f951 100644
--- a/src/gun_default_event_h.erl
+++ b/src/gun_default_event_h.erl
@@ -24,6 +24,7 @@
 -export([response_start/2]).
 -export([response_inform/2]).
 -export([response_headers/2]).
+-export([response_trailers/2]).
 -export([response_end/2]).
 -export([disconnect/2]).
 -export([terminate/2]).
@@ -55,6 +56,9 @@ response_inform(_EventData, State) ->
 response_headers(_EventData, State) ->
 	State.
 
+response_trailers(_EventData, State) ->
+	State.
+
 response_end(_EventData, State) ->
 	State.
 
diff --git a/src/gun_event.erl b/src/gun_event.erl
index 2a742a1..72abe24 100644
--- a/src/gun_event.erl
+++ b/src/gun_event.erl
@@ -89,6 +89,16 @@
 -callback response_inform(response_headers_event(), State) -> State.
 -callback response_headers(response_headers_event(), State) -> State.
 
+%% response_trailers.
+
+-type response_trailers_event() :: #{
+	stream_ref := reference(),
+	reply_to := pid(),
+	headers := [{binary(), binary()}]
+}.
+
+-callback response_trailers(response_trailers_event(), State) -> State.
+
 %% response_end.
 
 -type response_end_event() :: #{
@@ -122,7 +132,6 @@
 %% @todo origin_changed
 %% @todo transport_changed
 %% @todo protocol_changed
-%% @todo response_trailers
 %% @todo push_promise_start
 %% @todo push_promise_end
 %% @todo cancel_start
diff --git a/src/gun_http.erl b/src/gun_http.erl
index b7c5bc1..4acc3c4 100644
--- a/src/gun_http.erl
+++ b/src/gun_http.erl
@@ -197,10 +197,12 @@ handle(Data, State=#http_state{in=body_trailer, buffer=Buffer, connection=Conn,
 			{Trailers, Rest} = cow_http:parse_headers(Data2),
 			%% @todo We probably want to pass this to gun_content_handler?
 			ReplyTo ! {gun_trailers, self(), stream_ref(StreamRef), Trailers},
-			EvHandlerState = EvHandler:response_end(#{
+			ResponseEvent = #{
 				stream_ref => StreamRef,
 				reply_to => ReplyTo
-			}, EvHandlerState0),
+			},
+			EvHandlerState1 = EvHandler:response_trailers(ResponseEvent#{headers => Trailers}, EvHandlerState0),
+			EvHandlerState = EvHandler:response_end(ResponseEvent, EvHandlerState1),
 			case Conn of
 				keepalive ->
 					handle(Rest, end_stream(State#http_state{buffer= <<>>}), EvHandler, EvHandlerState);
diff --git a/src/gun_http2.erl b/src/gun_http2.erl
index 4814818..a1ba46e 100644
--- a/src/gun_http2.erl
+++ b/src/gun_http2.erl
@@ -124,10 +124,7 @@ frame(State=#http2_state{http2_machine=HTTP2Machine0}, Frame, EvHandler, EvHandl
 						stream_ref => StreamRef,
 						reply_to => ReplyTo
 					}, EvHandlerState0);
-				{ok, nofin} ->
-					%% @todo response_trailers.
-					EvHandlerState0;
-				%% This is an invalid headers frame.
+				%% Trailers or invalid header frame.
 				_ ->
 					EvHandlerState0
 			end;
@@ -259,10 +256,12 @@ trailers_frame(State, StreamID, Trailers, EvHandler, EvHandlerState0) ->
 	#stream{ref=StreamRef, reply_to=ReplyTo} = get_stream_by_id(State, StreamID),
 	%% @todo We probably want to pass this to gun_content_handler?
 	ReplyTo ! {gun_trailers, self(), StreamRef, Trailers},
-	EvHandlerState = EvHandler:response_end(#{
+	ResponseEvent = #{
 		stream_ref => StreamRef,
 		reply_to => ReplyTo
-	}, EvHandlerState0),
+	},
+	EvHandlerState1 = EvHandler:response_trailers(ResponseEvent#{headers => Trailers}, EvHandlerState0),
+	EvHandlerState = EvHandler:response_end(ResponseEvent, EvHandlerState1),
 	{maybe_delete_stream(State, StreamID, remote, fin), EvHandlerState}.
 
 rst_stream_frame(State=#http2_state{streams=Streams0}, StreamID, Reason) ->
diff --git a/test/event_SUITE.erl b/test/event_SUITE.erl
index 88f67d7..1863f15 100644
--- a/test/event_SUITE.erl
+++ b/test/event_SUITE.erl
@@ -255,6 +255,19 @@ response_headers(Config) ->
 	} = do_receive_event(?FUNCTION_NAME),
 	gun:close(Pid).
 
+response_trailers(Config) ->
+	doc("Confirm that the request_trailers event callback is called."),
+	{ok, Pid, _} = do_gun_open(Config),
+	{ok, _} = gun:await_up(Pid),
+	StreamRef = gun:get(Pid, "/trailers", [{<<"te">>, <<"trailers">>}]),
+	ReplyTo = self(),
+	#{
+		stream_ref := StreamRef,
+		reply_to := ReplyTo,
+		headers := [_|_]
+	} = do_receive_event(?FUNCTION_NAME),
+	gun:close(Pid).
+
 response_end(Config) ->
 	doc("Confirm that the request_headers event callback is called."),
 	do_response_end(Config, ?FUNCTION_NAME, "/"),
@@ -265,7 +278,7 @@ response_end(Config) ->
 do_response_end(Config, EventName, Path) ->
 	{ok, Pid, _} = do_gun_open(Config),
 	{ok, _} = gun:await_up(Pid),
-	StreamRef = gun:get(Pid, Path),
+	StreamRef = gun:get(Pid, Path, [{<<"te">>, <<"trailers">>}]),
 	ReplyTo = self(),
 	#{
 		stream_ref := StreamRef,
@@ -359,6 +372,10 @@ response_headers(EventData, Pid) ->
 	Pid ! {?FUNCTION_NAME, EventData},
 	Pid.
 
+response_trailers(EventData, Pid) ->
+	Pid ! {?FUNCTION_NAME, EventData},
+	Pid.
+
 response_end(EventData, Pid) ->
 	Pid ! {?FUNCTION_NAME, EventData},
 	Pid.
-- 
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