feat(api): replace all calls to http.Error with custom Error writer

api/http/docker_handler.go

@@ -135,7 +135,7 @@ type unixSocketHandler struct {
 func (h *unixSocketHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	conn, err := net.Dial("unix", h.path)
 	if err != nil {
-		http.Error(w, err.Error(), http.StatusInternalServerError)
+		Error(w, err, http.StatusInternalServerError, nil)
 		return
 	}
 	c := httputil.NewClientConn(conn, nil)
@@ -143,7 +143,7 @@ func (h *unixSocketHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 
 	res, err := c.Do(r)
 	if err != nil {
-		http.Error(w, err.Error(), http.StatusInternalServerError)
+		Error(w, err, http.StatusInternalServerError, nil)
 		return
 	}
 	defer res.Body.Close()
@@ -154,6 +154,6 @@ func (h *unixSocketHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 	if _, err := io.Copy(w, res.Body); err != nil {
-		http.Error(w, err.Error(), http.StatusInternalServerError)
+		Error(w, err, http.StatusInternalServerError, nil)
 	}
 }

api/http/handler.go

@@ -55,7 +55,9 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 // Error writes an API error message to the response and logger.
 func Error(w http.ResponseWriter, err error, code int, logger *log.Logger) {
 	// Log error.
-	logger.Printf("http error: %s (code=%d)", err, code)
+	if logger != nil {
+		logger.Printf("http error: %s (code=%d)", err, code)
+	}
 
 	// Write generic error response.
 	w.WriteHeader(code)

api/http/middleware.go

@@ -47,13 +47,13 @@ func (service *middleWareService) middleWareAuthenticate(next http.Handler) http
 		}
 
 		if token == "" {
-			http.Error(w, http.StatusText(http.StatusUnauthorized), http.StatusUnauthorized)
+			Error(w, portainer.ErrUnauthorized, http.StatusUnauthorized, nil)
 			return
 		}
 
 		err := service.jwtService.VerifyToken(token)
 		if err != nil {
-			http.Error(w, err.Error(), http.StatusUnauthorized)
+			Error(w, err, http.StatusUnauthorized, nil)
 			return
 		}
 

api/http/templates_handler.go

@@ -1,7 +1,6 @@
 package http
 
 import (
-	"fmt"
 	"io/ioutil"
 	"log"
 	"net/http"
@@ -40,15 +39,13 @@ func (handler *TemplatesHandler) handleGetTemplates(w http.ResponseWriter, r *ht
 
 	resp, err := http.Get(handler.templatesURL)
 	if err != nil {
-		log.Print(err)
-		http.Error(w, fmt.Sprintf("Error making request to %s: %s", handler.templatesURL, err.Error()), http.StatusInternalServerError)
+		Error(w, err, http.StatusInternalServerError, handler.Logger)
 		return
 	}
 	defer resp.Body.Close()
 	body, err := ioutil.ReadAll(resp.Body)
 	if err != nil {
-		log.Print(err)
-		http.Error(w, "Error reading body from templates URL", http.StatusInternalServerError)
+		Error(w, err, http.StatusInternalServerError, handler.Logger)
 		return
 	}
 	w.Header().Set("Content-Type", "application/json")