Make cowboy_compress_h add vary: accept-encoding

src/cowboy_compress_h.erl

@@ -176,10 +176,10 @@ gzip_response({response, Status, Headers, Body}, State) ->
 	after
 		zlib:close(Z)
 	end,
-	{{response, Status, Headers#{
+	{{response, Status, vary(Headers#{
 		<<"content-length">> => integer_to_binary(iolist_size(GzBody)),
 		<<"content-encoding">> => <<"gzip">>
-	}, GzBody}, State}.
+	}), GzBody}, State}.
 
 gzip_headers({headers, Status, Headers0}, State) ->
 	Z = zlib:open(),
@@ -187,9 +187,25 @@ gzip_headers({headers, Status, Headers0}, State) ->
 	%% @todo It might be good to allow them to be configured?
 	zlib:deflateInit(Z, default, deflated, 31, 8, default),
 	Headers = maps:remove(<<"content-length">>, Headers0),
-	{{headers, Status, Headers#{
+	{{headers, Status, vary(Headers#{
 		<<"content-encoding">> => <<"gzip">>
-	}}, State#state{deflate=Z}}.
+	})}, State#state{deflate=Z}}.
+
+%% We must add content-encoding to vary if it's not already there.
+vary(Headers=#{<<"vary">> := Vary}) ->
+	try cow_http_hd:parse_vary(iolist_to_binary(Vary)) of
+		'*' -> Headers;
+		List ->
+			case lists:member(<<"accept-encoding">>, List) of
+				true -> Headers;
+				false -> Headers#{<<"vary">> => [Vary, <<", accept-encoding">>]}
+			end
+	catch _:_ ->
+		%% The vary header is invalid. Probably empty. We replace it with ours.
+		Headers#{<<"vary">> => <<"accept-encoding">>}
+	end;
+vary(Headers) ->
+	Headers#{<<"vary">> => <<"accept-encoding">>}.
 
 %% It is not possible to combine zlib and the sendfile
 %% syscall as far as I can tell, because the zlib format

test/compress_SUITE.erl

@@ -67,6 +67,7 @@ gzip_accept_encoding_missing(Config) ->
 	{200, Headers, _} = do_get("/reply/large",
 		[], Config),
 	false = lists:keyfind(<<"content-encoding">>, 1, Headers),
+	false = lists:keyfind(<<"vary">>, 1, Headers),
 	{_, <<"100000">>} = lists:keyfind(<<"content-length">>, 1, Headers),
 	ok.
 
@@ -75,6 +76,7 @@ gzip_accept_encoding_no_gzip(Config) ->
 	{200, Headers, _} = do_get("/reply/large",
 		[{<<"accept-encoding">>, <<"compress">>}], Config),
 	false = lists:keyfind(<<"content-encoding">>, 1, Headers),
+	false = lists:keyfind(<<"vary">>, 1, Headers),
 	{_, <<"100000">>} = lists:keyfind(<<"content-length">>, 1, Headers),
 	ok.
 
@@ -84,6 +86,8 @@ gzip_reply_content_encoding(Config) ->
 		[{<<"accept-encoding">>, <<"gzip">>}], Config),
 	%% We set the content-encoding to compress; without actually compressing.
 	{_, <<"compress">>} = lists:keyfind(<<"content-encoding">>, 1, Headers),
+	%% The reply didn't include a vary header.
+	false = lists:keyfind(<<"vary">>, 1, Headers),
 	{_, <<"100000">>} = lists:keyfind(<<"content-length">>, 1, Headers),
 	ok.
 
@@ -92,6 +96,7 @@ gzip_reply_large_body(Config) ->
 	{200, Headers, GzBody} = do_get("/reply/large",
 		[{<<"accept-encoding">>, <<"gzip">>}], Config),
 	{_, <<"gzip">>} = lists:keyfind(<<"content-encoding">>, 1, Headers),
+	{_, <<"accept-encoding">>} = lists:keyfind(<<"vary">>, 1, Headers),
 	{_, Length} = lists:keyfind(<<"content-length">>, 1, Headers),
 	ct:log("Original length: 100000; compressed: ~s.", [Length]),
 	_ = zlib:gunzip(GzBody),
@@ -102,6 +107,7 @@ gzip_reply_sendfile(Config) ->
 	{200, Headers, Body} = do_get("/reply/sendfile",
 		[{<<"accept-encoding">>, <<"gzip">>}], Config),
 	false = lists:keyfind(<<"content-encoding">>, 1, Headers),
+	false = lists:keyfind(<<"vary">>, 1, Headers),
 	ct:log("Body received:~n~p~n", [Body]),
 	ok.
 
@@ -110,6 +116,7 @@ gzip_reply_small_body(Config) ->
 	{200, Headers, _} = do_get("/reply/small",
 		[{<<"accept-encoding">>, <<"gzip">>}], Config),
 	false = lists:keyfind(<<"content-encoding">>, 1, Headers),
+	false = lists:keyfind(<<"vary">>, 1, Headers),
 	{_, <<"100">>} = lists:keyfind(<<"content-length">>, 1, Headers),
 	ok.
 
@@ -118,6 +125,7 @@ gzip_stream_reply(Config) ->
 	{200, Headers, GzBody} = do_get("/stream_reply/large",
 		[{<<"accept-encoding">>, <<"gzip">>}], Config),
 	{_, <<"gzip">>} = lists:keyfind(<<"content-encoding">>, 1, Headers),
+	{_, <<"accept-encoding">>} = lists:keyfind(<<"vary">>, 1, Headers),
 	_ = zlib:gunzip(GzBody),
 	ok.
 
@@ -126,6 +134,7 @@ gzip_stream_reply_sendfile(Config) ->
 	{200, Headers, GzBody} = do_get("/stream_reply/sendfile",
 		[{<<"accept-encoding">>, <<"gzip">>}], Config),
 	{_, <<"gzip">>} = lists:keyfind(<<"content-encoding">>, 1, Headers),
+	{_, <<"accept-encoding">>} = lists:keyfind(<<"vary">>, 1, Headers),
 	_ = zlib:gunzip(GzBody),
 	ok.
 
@@ -134,6 +143,7 @@ gzip_stream_reply_sendfile_fin(Config) ->
 	{200, Headers, GzBody} = do_get("/stream_reply/sendfile_fin",
 		[{<<"accept-encoding">>, <<"gzip">>}], Config),
 	{_, <<"gzip">>} = lists:keyfind(<<"content-encoding">>, 1, Headers),
+	{_, <<"accept-encoding">>} = lists:keyfind(<<"vary">>, 1, Headers),
 	_ = zlib:gunzip(GzBody),
 	ok.
 
@@ -142,6 +152,7 @@ gzip_stream_reply_content_encoding(Config) ->
 	{200, Headers, Body} = do_get("/stream_reply/content-encoding",
 		[{<<"accept-encoding">>, <<"gzip">>}], Config),
 	{_, <<"compress">>} = lists:keyfind(<<"content-encoding">>, 1, Headers),
+	false = lists:keyfind(<<"vary">>, 1, Headers),
 	100000 = iolist_size(Body),
 	ok.
 
@@ -164,6 +175,7 @@ opts_compress_buffering_false(Config0) ->
 			[{<<"accept-encoding">>, <<"gzip">>}]),
 		{response, nofin, 200, Headers} = gun:await(ConnPid, Ref),
 		{_, <<"gzip">>} = lists:keyfind(<<"content-encoding">>, 1, Headers),
+		{_, <<"accept-encoding">>} = lists:keyfind(<<"vary">>, 1, Headers),
 		Z = zlib:open(),
 		zlib:inflateInit(Z, 31),
 		{data, nofin, Data1} = gun:await(ConnPid, Ref, 500),
@@ -195,6 +207,7 @@ opts_compress_buffering_true(Config0) ->
 			[{<<"accept-encoding">>, <<"gzip">>}]),
 		{response, nofin, 200, Headers} = gun:await(ConnPid, Ref),
 		{_, <<"gzip">>} = lists:keyfind(<<"content-encoding">>, 1, Headers),
+		{_, <<"accept-encoding">>} = lists:keyfind(<<"vary">>, 1, Headers),
 		Z = zlib:open(),
 		zlib:inflateInit(Z, 31),
 		%% The data gets buffered because it is too small.
@@ -229,6 +242,7 @@ set_options_compress_buffering_false(Config0) ->
 			[{<<"accept-encoding">>, <<"gzip">>}]),
 		{response, nofin, 200, Headers} = gun:await(ConnPid, Ref),
 		{_, <<"gzip">>} = lists:keyfind(<<"content-encoding">>, 1, Headers),
+		{_, <<"accept-encoding">>} = lists:keyfind(<<"vary">>, 1, Headers),
 		Z = zlib:open(),
 		zlib:inflateInit(Z, 31),
 		{data, nofin, Data1} = gun:await(ConnPid, Ref, 500),
@@ -260,6 +274,7 @@ set_options_compress_buffering_true(Config0) ->
 			[{<<"accept-encoding">>, <<"gzip">>}]),
 		{response, nofin, 200, Headers} = gun:await(ConnPid, Ref),
 		{_, <<"gzip">>} = lists:keyfind(<<"content-encoding">>, 1, Headers),
+		{_, <<"accept-encoding">>} = lists:keyfind(<<"vary">>, 1, Headers),
 		Z = zlib:open(),
 		zlib:inflateInit(Z, 31),
 		%% The data gets buffered because it is too small.
@@ -281,5 +296,46 @@ set_options_compress_threshold_0(Config) ->
 	{200, Headers, GzBody} = do_get("/reply/set_options_threshold0",
 		[{<<"accept-encoding">>, <<"gzip">>}], Config),
 	{_, <<"gzip">>} = lists:keyfind(<<"content-encoding">>, 1, Headers),
+	{_, <<"accept-encoding">>} = lists:keyfind(<<"vary">>, 1, Headers),
 	_ = zlib:gunzip(GzBody),
 	ok.
+
+vary_accept(Config) ->
+	doc("Add accept-encoding to vary when the response has a 'vary: accept' header."),
+	{200, Headers, _} = do_get("/reply/vary", [
+		{<<"accept-encoding">>, <<"gzip">>},
+		{<<"x-test-vary">>, <<"accept">>}
+	], Config),
+	{_, <<"gzip">>} = lists:keyfind(<<"content-encoding">>, 1, Headers),
+	{_, <<"accept, accept-encoding">>} = lists:keyfind(<<"vary">>, 1, Headers),
+	ok.
+
+vary_accept_accept_encoding(Config) ->
+	doc("Don't change the vary value when the response has a 'vary: accept, accept-encoding' header."),
+	{200, Headers, _} = do_get("/reply/vary", [
+		{<<"accept-encoding">>, <<"gzip">>},
+		{<<"x-test-vary">>, <<"accept, accept-encoding">>}
+	], Config),
+	{_, <<"gzip">>} = lists:keyfind(<<"content-encoding">>, 1, Headers),
+	{_, <<"accept, accept-encoding">>} = lists:keyfind(<<"vary">>, 1, Headers),
+	ok.
+
+vary_empty(Config) ->
+	doc("Add accept-encoding to vary when the response has an empty vary header."),
+	{200, Headers, _} = do_get("/reply/vary", [
+		{<<"accept-encoding">>, <<"gzip">>},
+		{<<"x-test-vary">>, <<>>}
+	], Config),
+	{_, <<"gzip">>} = lists:keyfind(<<"content-encoding">>, 1, Headers),
+	{_, <<"accept-encoding">>} = lists:keyfind(<<"vary">>, 1, Headers),
+	ok.
+
+vary_wildcard(Config) ->
+	doc("Don't change the vary value when the response has a 'vary: *' header."),
+	{200, Headers, _} = do_get("/reply/vary", [
+		{<<"accept-encoding">>, <<"gzip">>},
+		{<<"x-test-vary">>, <<"*">>}
+	], Config),
+	{_, <<"gzip">>} = lists:keyfind(<<"content-encoding">>, 1, Headers),
+	{_, <<"*">>} = lists:keyfind(<<"vary">>, 1, Headers),
+	ok.

test/handlers/compress_h.erl

@@ -11,6 +11,9 @@ init(Req0, State=reply) ->
 			cowboy_req:reply(200, #{}, lists:duplicate(100, $a), Req0);
 		<<"large">> ->
 			cowboy_req:reply(200, #{}, lists:duplicate(100000, $a), Req0);
+		<<"vary">> ->
+			Vary = cowboy_req:header(<<"x-test-vary">>, Req0),
+			cowboy_req:reply(200, #{<<"vary">> => Vary}, lists:duplicate(100000, $a), Req0);
 		<<"over-threshold">> ->
 			cowboy_req:reply(200, #{}, lists:duplicate(200, $a), Req0);
 		<<"content-encoding">> ->