support weak etag

etag.go

@@ -14,7 +14,7 @@ import (
 )
 
 // Version is this package's version.
-const Version = "0.1.0"
+const Version = "0.2.0"
 
 type hashWriter struct {
 	rw     http.ResponseWriter
@@ -51,7 +51,7 @@ func writeRaw(res http.ResponseWriter, hw hashWriter) {
 }
 
 // Handler wraps the http.Handler h with ETag support.
-func Handler(h http.Handler) http.Handler {
+func Handler(h http.Handler, weak bool) http.Handler {
 	return http.HandlerFunc(func(res http.ResponseWriter, req *http.Request) {
 		hw := hashWriter{rw: res, hash: sha1.New(), buf: bytes.NewBuffer(nil)}
 		h.ServeHTTP(&hw, req)
@@ -66,8 +66,14 @@ func Handler(h http.Handler) http.Handler {
 			return
 		}
 
-		resHeader.Set(headers.ETag, fmt.Sprintf("%v-%v", strconv.Itoa(hw.len),
-			hex.EncodeToString(hw.hash.Sum(nil))))
+		etag := fmt.Sprintf("%v-%v", strconv.Itoa(hw.len),
+			hex.EncodeToString(hw.hash.Sum(nil)))
+
+		if weak {
+			etag = "w/" + etag
+		}
+
+		resHeader.Set(headers.ETag, etag)
 
 		if fresh.IsFresh(req.Header, resHeader) {
 			res.WriteHeader(http.StatusNotModified)

etag_test.go

@@ -24,7 +24,7 @@ type EmptyEtagSuite struct {
 
 func (s *EmptyEtagSuite) SetupTest() {
 	mux := http.NewServeMux()
-	mux.Handle("/", Handler(http.HandlerFunc(emptyHandlerFunc)))
+	mux.Handle("/", Handler(http.HandlerFunc(emptyHandlerFunc), false))
 
 	s.server = httptest.NewServer(mux)
 }
@@ -44,14 +44,20 @@ func TestEmptyEtag(t *testing.T) {
 type EtagSuite struct {
 	suite.Suite
 
-	server *httptest.Server
+	server     *httptest.Server
+	weakServer *httptest.Server
 }
 
 func (s *EtagSuite) SetupTest() {
 	mux := http.NewServeMux()
-	mux.Handle("/", Handler(http.HandlerFunc(handlerFunc)))
+	mux.Handle("/", Handler(http.HandlerFunc(handlerFunc), false))
 
 	s.server = httptest.NewServer(mux)
+
+	wmux := http.NewServeMux()
+	wmux.Handle("/", Handler(http.HandlerFunc(handlerFunc), true))
+
+	s.weakServer = httptest.NewServer(wmux)
 }
 
 func (s EtagSuite) TestEtagExists() {
@@ -66,6 +72,18 @@ func (s EtagSuite) TestEtagExists() {
 	s.Equal(fmt.Sprintf("%v-%v", len(testStrBytes), hex.EncodeToString(h.Sum(nil))), res.Header.Get(headers.ETag))
 }
 
+func (s EtagSuite) TestWeakEtagExists() {
+	res, err := http.Get(s.weakServer.URL + "/")
+
+	s.Nil(err)
+	s.Equal(http.StatusOK, res.StatusCode)
+
+	h := sha1.New()
+	h.Write(testStrBytes)
+
+	s.Equal(fmt.Sprintf("w/%v-%v", len(testStrBytes), hex.EncodeToString(h.Sum(nil))), res.Header.Get(headers.ETag))
+}
+
 func (s EtagSuite) TestMatch() {
 	req, err := http.NewRequest(http.MethodGet, s.server.URL+"/", nil)
 	s.Nil(err)

example_test.go

@@ -12,5 +12,5 @@ func Example() {
 		res.Write([]byte("Hello World"))
 	})
 
-	http.ListenAndServe(":8080", etag.Handler(mux))
+	http.ListenAndServe(":8080", etag.Handler(mux, false))
 }