contrib/net/http: implement rwUnwrapper

contrib/net/http/http_test.go

@@ -6,11 +6,13 @@
 package http
 
 import (
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"strings"
 	"sync"
 	"testing"
+	"time"
 
 	"gopkg.in/DataDog/dd-trace-go.v1/contrib/internal/namingschematest"
 	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/ext"
@@ -21,6 +23,7 @@ import (
 	"gopkg.in/DataDog/dd-trace-go.v1/internal/normalizer"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestWithHeaderTags(t *testing.T) {
@@ -523,6 +526,48 @@ func TestServerNamingSchema(t *testing.T) {
 	namingschematest.NewHTTPServerTest(genSpans, "http.router")(t)
 }
 
+// TestUnwrap tests the implementation of the rwUnwrapper interface, which is used internally
+// by the standard library: https://github.com/golang/go/blob/6d89b38ed86e0bfa0ddaba08dc4071e6bb300eea/src/net/http/responsecontroller.go#L42-L44
+// See also: https://github.com/DataDog/dd-trace-go/issues/2674
+func TestUnwrap(t *testing.T) {
+	fn := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		rc := http.NewResponseController(w)
+
+		// Use the SetReadDeadline and SetWriteDeadline methods, which are not explicitly implemented in the trace_gen.go
+		// generated file. Before the Unwrap change, these methods returned a "feature not supported" error.
+
+		err := rc.SetReadDeadline(time.Now().Add(10 * time.Second))
+		if err != nil {
+			w.WriteHeader(http.StatusInternalServerError)
+			w.Write([]byte(err.Error()))
+			return
+		}
+		err = rc.SetWriteDeadline(time.Now().Add(10 * time.Second))
+		if err != nil {
+			w.WriteHeader(http.StatusInternalServerError)
+			w.Write([]byte(err.Error()))
+			return
+		}
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte("OK"))
+	})
+
+	h := WrapHandler(fn, "service-name", "resource-name")
+	srv := httptest.NewServer(h)
+	defer srv.Close()
+
+	resp, err := srv.Client().Get(srv.URL + "/")
+	require.NoError(t, err)
+	defer resp.Body.Close()
+
+	b, err := io.ReadAll(resp.Body)
+	require.NoError(t, err)
+	respText := string(b)
+
+	assert.Equal(t, http.StatusOK, resp.StatusCode)
+	assert.Equal(t, "OK", respText)
+}
+
 func router(muxOpts ...Option) http.Handler {
 	defaultOpts := []Option{
 		WithServiceName("my-service"),

contrib/net/http/trace.go

@@ -111,3 +111,8 @@ func (w *responseWriter) WriteHeader(status int) {
 	w.ResponseWriter.WriteHeader(status)
 	w.status = status
 }
+
+// Unwrap returns the underlying wrapped http.ResponseWriter.
+func (w *responseWriter) Unwrap() http.ResponseWriter {
+	return w.ResponseWriter
+}