net/http: don't MIME sniff if handler set an empty string Content-Type

Fixes #5953 R=golang-dev, dsymonds CC=golang-dev https://golang.org/cl/12117043

net/http: don't MIME sniff if handler set an empty string Content-Type
Fixes #5953 R=golang-dev, dsymonds CC=golang-dev https://golang.org/cl/12117043
252c107f · Brad Fitzpatrick · 184b02ea · 252c107f · 252c107f
Commit 252c107f authored Aug 01, 2013 by Brad Fitzpatrick
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Showing with 26 additions and 1 deletion

server.go src/pkg/net/http/server.go +2 -1

sniff_test.go src/pkg/net/http/sniff_test.go +24 -0

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--- a/src/pkg/net/http/server.go
+++ b/src/pkg/net/http/server.go
@@ -792,7 +792,8 @@ func (cw *chunkWriter) writeHeader(p []byte) {
 		}
 	} else {
 		// If no content type, apply sniffing algorithm to body.
-		if header.get("Content-Type") == "" && w.req.Method != "HEAD" {
+		_, haveType := header["Content-Type"]
+		if !haveType && w.req.Method != "HEAD" {
 			setHeader.contentType = DetectContentType(p)
 		}
 	}

--- a/src/pkg/net/http/sniff_test.go
+++ b/src/pkg/net/http/sniff_test.go
@@ -12,6 +12,7 @@ import (
 	"log"
 	. "net/http"
 	"net/http/httptest"
+	"reflect"
 	"strconv"
 	"strings"
 	"testing"
@@ -84,6 +85,29 @@ func TestServerContentType(t *testing.T) {
 	}
 }

+// Issue 5953: shouldn't sniff if the handler set a Content-Type header,
+// even if it's the empty string.
+func TestServerIssue5953(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Header()["Content-Type"] = []string{""}
+		fmt.Fprintf(w, "<html><head></head><body>hi</body></html>")
+	}))
+	defer ts.Close()
+
+	resp, err := Get(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	got := resp.Header["Content-Type"]
+	want := []string{""}
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("Content-Type = %q; want %q", got, want)
+	}
+	resp.Body.Close()
+}
+
 func TestContentTypeWithCopy(t *testing.T) {
 	defer afterTest(t)