Show error messages in UI if something goes wrong

cmd/backend/images.go

@@ -2,6 +2,7 @@ package backend
 
 import (
 	"fmt"
+	"image"
 	"io"
 	"os"
 
@@ -10,9 +11,14 @@ import (
 	"github.com/google/uuid"
 )
 
+var ErrUnsupportedFormat error = image.ErrFormat // used internally by imaging
+
 func SaveImage(c *Config, src io.Reader) (string, error) {
 	img, err := imaging.Decode(src, imaging.AutoOrientation(true))
 	if err != nil {
+		if err == ErrUnsupportedFormat {
+			return "", ErrUnsupportedFormat
+		}
 		return "", fmt.Errorf("error decoding image: %v", err)
 	}
 

cmd/backend/users.go

@@ -47,7 +47,7 @@ func (db *DB) AddUser(u *User, pass string) (int64, error) {
 	return id, nil
 }
 
-func (db *DB) GetID(userName string) (int64, bool) {
+func (db *DB) GetID(userName string) int64 {
 	var id int64
 
 	query := `
@@ -56,11 +56,11 @@ func (db *DB) GetID(userName string) (int64, bool) {
     WHERE username = ?
     `
 	row := db.QueryRow(query, userName)
-	if err := row.Scan(&id); err != nil {
-		return 0, false
+	if err := row.Scan(&id); err != nil { // seems like the only possible error is ErrNoRows
+		return 0
 	}
 
-	return id, true
+	return id
 }
 
 func (db *DB) CheckPassword(id int64, pass string) error {
@@ -146,7 +146,7 @@ func (db *DB) GetUser(id int64) (*User, error) {
 	return user, nil
 }
 
-func (db *DB) UpdateOwnAttributes(id int64, user, first, last, oldPass, newPass, newPass2 string) error {
+func (db *DB) UpdateOwnUserAttributes(id int64, user, first, last, oldPass, newPass, newPass2 string) error {
 	passwordEmpty := true
 	if len(newPass) > 0 || len(newPass2) > 0 {
 		if newPass != newPass2 {
@@ -228,7 +228,7 @@ func (db *DB) AddFirstUser(u *User, pass string) (int64, error) {
 				if err = tx.Commit(); err != nil {
 					return 0, fmt.Errorf("error committing transaction: %v", err)
 				}
-				return 2, nil
+				return -1, nil
 			}
 
 			hashedPass, err := bcrypt.GenerateFromPassword([]byte(pass), bcrypt.DefaultCost)