Re-use username for UID if it exists

internal/alpine/users.go

@@ -6,34 +6,34 @@ import (
 )
 
 // CreateUser creates a user in Alpine with the given UID.
-func (c *configurator) CreateUser(username string, uid int) error {
+func (c *configurator) CreateUser(username string, uid int) (createdUsername string, err error) {
 	UIDStr := fmt.Sprintf("%d", uid)
 	u, err := c.lookupUID(UIDStr)
 	_, unknownUID := err.(user.UnknownUserIdError)
 	if err != nil && !unknownUID {
-		return fmt.Errorf("cannot create user: %w", err)
+		return "", fmt.Errorf("cannot create user: %w", err)
 	} else if u != nil {
 		if u.Username == username {
-			return nil
+			return "", nil
 		}
-		return fmt.Errorf("user with ID %d exists with username %q instead of %q", uid, u.Username, username)
+		return u.Username, nil
 	}
 	u, err = c.lookupUser(username)
 	_, unknownUsername := err.(user.UnknownUserError)
 	if err != nil && !unknownUsername {
-		return fmt.Errorf("cannot create user: %w", err)
+		return "", fmt.Errorf("cannot create user: %w", err)
 	} else if u != nil {
-		return fmt.Errorf("cannot create user: user with name %s already exists for ID %s instead of %d",
+		return "", fmt.Errorf("cannot create user: user with name %s already exists for ID %s instead of %d",
 			username, u.Uid, uid)
 	}
 	passwd, err := c.fileManager.ReadFile("/etc/passwd")
 	if err != nil {
-		return fmt.Errorf("cannot create user: %w", err)
+		return "", fmt.Errorf("cannot create user: %w", err)
 	}
 	passwd = append(passwd, []byte(fmt.Sprintf("%s:x:%d:::/dev/null:/sbin/nologin\n", username, uid))...)
 
 	if err := c.fileManager.WriteToFile("/etc/passwd", passwd); err != nil {
-		return fmt.Errorf("cannot create user: %w", err)
+		return "", fmt.Errorf("cannot create user: %w", err)
 	}
-	return nil
+	return username, nil
 }