ezhttp: don't override 'Accept' header with RespondsJSON...()

Author: joonas-fi

net/http/ezhttp/conffns.go

@@ -68,7 +68,9 @@ func RespondsJSONDisallowUnknownFields(obj interface{}) ConfigPiece {
 
 func respondsJSON(ref interface{}, allowUnknownFields bool) ConfigPiece {
 	return After(func(conf *Config) {
-		conf.Request.Header.Set("Accept", jsonContentType)
+		if conf.Request.Header.Get("Accept") == "" { // don't override if we have explicit `Accept` header
+			conf.Request.Header.Set("Accept", jsonContentType)
+		}
 
 		conf.OutputsJson = true
 		conf.OutputsJsonRef = ref

net/http/ezhttp/ezhttp_test.go

@@ -150,6 +150,23 @@ func TestAuthBearer(t *testing.T) {
 	assert.EqualString(t, string(respBody), "Echoing Authorization: Bearer LOLOLOLOL")
 }
 
+func TestRespondsJSONDoesntOverrideExplicitAccept(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		fmt.Fprintf(w, `{"AcceptEchoed": "%s"}`, r.Header.Get("Accept"))
+	}))
+	defer ts.Close()
+
+	respJSON := struct {
+		AcceptEchoed string
+	}{}
+
+	// before the fix, RespondsJSONDisallowUnknownFields() used to override explicit header
+	_, err := Get(context.TODO(), ts.URL, Header("Accept", "text/foobar"), RespondsJSONDisallowUnknownFields(&respJSON))
+	assert.Ok(t, err)
+
+	assert.EqualString(t, respJSON.AcceptEchoed, "text/foobar")
+}
+
 func TestAuthBasic(t *testing.T) {
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		fmt.Fprintf(w, "Echoing Authorization: %s", r.Header.Get("Authorization"))