Always make fatal errors json-serializable (#14396)

cmd/error.go

@@ -28,6 +28,27 @@ const (
 	ClassSponsorship
 )
 
+// FatalError is an error that can be marshaled
+type FatalError struct {
+	err error
+}
+
+func (e *FatalError) Error() string {
+	return e.err.Error()
+}
+
+func (e FatalError) MarshalJSON() ([]byte, error) {
+	if je, ok := e.err.(json.Marshaler); ok {
+		return je.MarshalJSON()
+	}
+
+	return json.Marshal(struct {
+		Error string `json:"error"`
+	}{
+		Error: e.err.Error(),
+	})
+}
+
 // DeviceError indicates the specific device that failed
 type DeviceError struct {
 	Name string

cmd/helper.go

@@ -75,23 +75,25 @@ func shutdownDoneC() <-chan struct{} {
 	return doneC
 }
 
-func wrapError(err error) error {
-	if err != nil {
-		var opErr *net.OpError
-		var pathErr *os.PathError
+func wrapFatalError(err error) error {
+	if err == nil {
+		return nil
+	}
+
+	var opErr *net.OpError
+	var pathErr *os.PathError
 
-		switch {
-		case errors.As(err, &opErr):
-			if opErr.Op == "listen" && strings.Contains(opErr.Error(), "address already in use") {
-				err = fmt.Errorf("could not open port- check that evcc is not already running (%w)", err)
-			}
+	switch {
+	case errors.As(err, &opErr):
+		if opErr.Op == "listen" && strings.Contains(opErr.Error(), "address already in use") {
+			err = fmt.Errorf("could not open port- check that evcc is not already running (%w)", err)
+		}
 
-		case errors.As(err, &pathErr):
-			if pathErr.Op == "remove" && strings.Contains(pathErr.Error(), "operation not permitted") {
-				err = fmt.Errorf("could not remove file- check that evcc is not already running (%w)", err)
-			}
+	case errors.As(err, &pathErr):
+		if pathErr.Op == "remove" && strings.Contains(pathErr.Error(), "operation not permitted") {
+			err = fmt.Errorf("could not remove file- check that evcc is not already running (%w)", err)
 		}
 	}
 
-	return err
+	return &FatalError{err}
 }

cmd/root.go

@@ -291,7 +291,7 @@ func runRoot(cmd *cobra.Command, args []string) {
 
 	if err != nil {
 		// improve error message
-		err = wrapError(err)
+		err = wrapFatalError(err)
 		valueChan <- util.Param{Key: keys.Fatal, Val: err}
 
 		// TODO stop reboot loop if user updates config (or show countdown in UI)
@@ -307,5 +307,5 @@ func runRoot(cmd *cobra.Command, args []string) {
 	// uds health check listener
 	go server.HealthListener(site)
 
-	log.FATAL.Println(wrapError(httpd.ListenAndServe()))
+	log.FATAL.Println(wrapFatalError(httpd.ListenAndServe()))
 }