Improve error messages (#6014)

cmd/helper.go

@@ -3,6 +3,7 @@ package cmd
 import (
 	"errors"
 	"fmt"
+	"net"
 	"os"
 	"path/filepath"
 	"regexp"
@@ -99,3 +100,24 @@ func shutdownDoneC() <-chan struct{} {
 	go shutdown.Cleanup(doneC)
 	return doneC
 }
+
+func wrapErrors(err error) error {
+	if err != 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)
+			}
+
+		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
+}

cmd/root.go

@@ -268,6 +268,9 @@ func runRoot(cmd *cobra.Command, args []string) {
 			once.Do(func() { close(stopC) }) // signal loop to end
 		})
 
+		// improve error message
+		err = wrapErrors(err)
+
 		publishErrorInfo(valueChan, cfgFile, err)
 
 		log.FATAL.Println(err)
@@ -282,5 +285,5 @@ func runRoot(cmd *cobra.Command, args []string) {
 	// uds health check listener
 	go server.HealthListener(site)
 
-	log.FATAL.Println(httpd.ListenAndServe())
+	log.FATAL.Println(wrapErrors(httpd.ListenAndServe()))
 }