net/http/httputil: allow MIME parameters when detecting SSE in ReverseProxy

This change allows httputil.ReverseProxy to detect SSE (server-sent events)
content when the response's Content-Type header includes MIME parameters,
such as "text/event-stream;charset=utf-8".

Prior to this change the value of the Content-Type header was compared
directly to the literal "text/event-stream". This caused a false-negative
which failed to set the FlushInterval correctly when MIME parameters were
present.

Change-Id: If8bb43efb78787b6519d7fe7599ca018a0da0023
GitHub-Last-Rev: 224518c5eb9686ee050c79f5f853ebacfdf6fc42
GitHub-Pull-Request: golang/go#48427
Reviewed-on: https://go-review.googlesource.com/c/go/+/350509
Trust: Alexander Rakoczy <alex@golang.org>
Trust: Damien Neil <dneil@google.com>
Run-TryBot: Alexander Rakoczy <alex@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Damien Neil <dneil@google.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/src/net/http/httputil/reverseproxy_test.go b/src/net/http/httputil/reverseproxy_test.go
index 4b6ad77a29..90e8903e9c 100644
--- a/src/net/http/httputil/reverseproxy_test.go
+++ b/src/net/http/httputil/reverseproxy_test.go
@@ -1195,6 +1195,26 @@ func TestSelectFlushInterval(t *testing.T) {
 			want: -1,
 		},
 		{
+			name: "server-sent events with media-type parameters overrides non-zero",
+			res: &http.Response{
+				Header: http.Header{
+					"Content-Type": {"text/event-stream;charset=utf-8"},
+				},
+			},
+			p:    &ReverseProxy{FlushInterval: 123},
+			want: -1,
+		},
+		{
+			name: "server-sent events with media-type parameters overrides zero",
+			res: &http.Response{
+				Header: http.Header{
+					"Content-Type": {"text/event-stream;charset=utf-8"},
+				},
+			},
+			p:    &ReverseProxy{FlushInterval: 0},
+			want: -1,
+		},
+		{
 			name: "Content-Length: -1, overrides non-zero",
 			res: &http.Response{
 				ContentLength: -1,