fix: prompt for user action to set an instance ID on upgrade

internal/config/validate.go

@@ -10,14 +10,19 @@ import (
 	"github.com/garethgeorge/backrest/internal/config/validationutil"
 	"github.com/gitploy-io/cronexpr"
 	"github.com/hashicorp/go-multierror"
+	"go.uber.org/zap"
 	"google.golang.org/protobuf/proto"
 )
 
 func ValidateConfig(c *v1.Config) error {
 	var err error
 
 	if e := validationutil.ValidateID(c.Instance, validationutil.IDMaxLen); e != nil {
-		err = multierror.Append(err, fmt.Errorf("instance ID %q invalid: %w", c.Instance, e))
+		if errors.Is(e, validationutil.ErrEmpty) {
+			zap.L().Warn("ACTION REQUIRED: instance ID is empty, will be required in a future update. Please open the backrest UI to set a unique instance ID. Until fixed this warning (and related errors) will print periodically.")
+		} else {
+			err = multierror.Append(err, fmt.Errorf("instance ID %q invalid: %w", c.Instance, e))
+		}
 	}
 
 	repos := make(map[string]*v1.Repo)

internal/config/validationutil/validationutil.go

@@ -12,6 +12,12 @@ var (
 	idRegex         = regexp.MustCompile(`[a-zA-Z0-9_\-\.]*`)  // matches a valid ID (including empty string)
 )
 
+var (
+	ErrEmpty        = errors.New("empty")
+	ErrTooLong      = errors.New("too long")
+	ErrInvalidChars = errors.New("contains invalid characters")
+)
+
 func SanitizeID(id string) string {
 	return sanitizeIDRegex.ReplaceAllString(id, "_")
 }
@@ -21,13 +27,13 @@ func SanitizeID(id string) string {
 // The maxLen parameter is the maximum length of the ID. If maxLen is 0, the ID length is not checked.
 func ValidateID(id string, maxLen int) error {
 	if !idRegex.MatchString(id) {
-		return errors.New("contains invalid characters")
+		return ErrInvalidChars
 	}
 	if len(id) == 0 {
-		return errors.New("empty")
+		return ErrEmpty
 	}
 	if maxLen > 0 && len(id) > maxLen {
-		return fmt.Errorf("too long (> %d chars)", maxLen)
+		return fmt.Errorf("(> %d chars): %w", maxLen, ErrTooLong)
 	}
 	return nil
 }