Fix #198 (#781)

* Add new function to Render interface for writing content type only

* Add support for the new function in Render interface for writing content-type only

* Fix unhandled merge conflict in context_test.go

* Update vendor.json

render/data.go

@@ -11,10 +11,13 @@ type Data struct {
 	Data        []byte
 }
 
-func (r Data) Render(w http.ResponseWriter) error {
-	if len(r.ContentType) > 0 {
-		w.Header()["Content-Type"] = []string{r.ContentType}
-	}
-	w.Write(r.Data)
-	return nil
+// Render (Data) writes data with custom ContentType
+func (r Data) Render(w http.ResponseWriter) (err error) {
+	r.WriteContentType(w)
+	_, err = w.Write(r.Data)
+	return
+}
+
+func (r Data) WriteContentType(w http.ResponseWriter) {
+	writeContentType(w, []string{r.ContentType})
 }

render/html.go

@@ -58,9 +58,14 @@ func (r HTMLDebug) loadTemplate() *template.Template {
 }
 
 func (r HTML) Render(w http.ResponseWriter) error {
-	writeContentType(w, htmlContentType)
+	r.WriteContentType(w)
+
 	if len(r.Name) == 0 {
 		return r.Template.Execute(w, r.Data)
 	}
 	return r.Template.ExecuteTemplate(w, r.Name, r.Data)
 }
+
+func (r HTML) WriteContentType(w http.ResponseWriter) {
+	writeContentType(w, htmlContentType)
+}

render/json.go

@@ -21,18 +21,15 @@ type (
 
 var jsonContentType = []string{"application/json; charset=utf-8"}
 
-func (r JSON) Render(w http.ResponseWriter) error {
-	return WriteJSON(w, r.Data)
+func (r JSON) Render(w http.ResponseWriter) (err error) {
+	if err = WriteJSON(w, r.Data); err != nil {
+		panic(err)
+	}
+	return
 }
 
-func (r IndentedJSON) Render(w http.ResponseWriter) error {
+func (r JSON) WriteContentType(w http.ResponseWriter) {
 	writeContentType(w, jsonContentType)
-	jsonBytes, err := json.MarshalIndent(r.Data, "", "    ")
-	if err != nil {
-		return err
-	}
-	w.Write(jsonBytes)
-	return nil
 }
 
 func WriteJSON(w http.ResponseWriter, obj interface{}) error {
@@ -44,3 +41,17 @@ func WriteJSON(w http.ResponseWriter, obj interface{}) error {
 	w.Write(jsonBytes)
 	return nil
 }
+
+func (r IndentedJSON) Render(w http.ResponseWriter) error {
+	r.WriteContentType(w)
+	jsonBytes, err := json.MarshalIndent(r.Data, "", "    ")
+	if err != nil {
+		return err
+	}
+	w.Write(jsonBytes)
+	return nil
+}
+
+func (r IndentedJSON) WriteContentType(w http.ResponseWriter) {
+	writeContentType(w, jsonContentType)
+}

render/redirect.go

@@ -22,3 +22,5 @@ func (r Redirect) Render(w http.ResponseWriter) error {
 	http.Redirect(w, r.Request, r.Location, r.Code)
 	return nil
 }
+
+func (r Redirect) WriteContentType(http.ResponseWriter) {}

render/render.go

@@ -8,6 +8,7 @@ import "net/http"
 
 type Render interface {
 	Render(http.ResponseWriter) error
+	WriteContentType(w http.ResponseWriter)
 }
 
 var (

render/text.go

@@ -22,9 +22,12 @@ func (r String) Render(w http.ResponseWriter) error {
 	return nil
 }
 
+func (r String) WriteContentType(w http.ResponseWriter) {
+	writeContentType(w, plainContentType)
+}
+
 func WriteString(w http.ResponseWriter, format string, data []interface{}) {
 	writeContentType(w, plainContentType)
-
 	if len(data) > 0 {
 		fmt.Fprintf(w, format, data...)
 	} else {

render/xml.go

@@ -16,6 +16,10 @@ type XML struct {
 var xmlContentType = []string{"application/xml; charset=utf-8"}
 
 func (r XML) Render(w http.ResponseWriter) error {
-	writeContentType(w, xmlContentType)
+	r.WriteContentType(w)
 	return xml.NewEncoder(w).Encode(r.Data)
 }
+
+func (r XML) WriteContentType(w http.ResponseWriter) {
+	writeContentType(w, xmlContentType)
+}

render/yaml.go

@@ -17,7 +17,7 @@ type YAML struct {
 var yamlContentType = []string{"application/x-yaml; charset=utf-8"}
 
 func (r YAML) Render(w http.ResponseWriter) error {
-	writeContentType(w, yamlContentType)
+	r.WriteContentType(w)
 
 	bytes, err := yaml.Marshal(r.Data)
 	if err != nil {
@@ -27,3 +27,7 @@ func (r YAML) Render(w http.ResponseWriter) error {
 	w.Write(bytes)
 	return nil
 }
+
+func (r YAML) WriteContentType(w http.ResponseWriter) {
+	writeContentType(w, yamlContentType)
+}