Reuse message across tag validation

Author: anisaoshafi

internal/api/client.go

@@ -313,7 +313,7 @@ func (c *PlatformClient) GetLicense(ctx context.Context, licReq *LicenseRequest)
 		if strings.Contains(detail, "licensing.license.format") {
 			return nil, &LicenseError{
 				Status:  statusCode,
-				Message: "unsupported image tag — check the tag in your config file",
+				Message: version.UnsupportedTagMessage(),
 				Detail:  detail,
 			}
 		}

internal/config/containers.go

@@ -7,7 +7,8 @@ import (
 	"regexp"
 	"strconv"
 	"strings"
-	"time"
+
+	"github.com/localstack/lstk/internal/version"
 )
 
 type EmulatorType string
@@ -120,22 +121,12 @@ var zeroPaddedMonthTagRe = regexp.MustCompile(`^(\d{4}\.)0([1-9].*)$`)
 // must not start with a dot or hyphen; max 128 characters.
 var validTagRe = regexp.MustCompile(`^[a-zA-Z0-9_][a-zA-Z0-9._-]*$`)
 
-// prevMonthExample returns the previous calendar month as a tag example, e.g. "2026.4".
-func prevMonthExample() string {
-	y, m, _ := time.Now().Date()
-	m--
-	if m == 0 {
-		m, y = 12, y-1
-	}
-	return fmt.Sprintf("%d.%d", y, int(m))
-}
-
 func validateTag(tag string) error {
 	if tag == "" {
 		return nil
 	}
 	if len(tag) > 128 || !validTagRe.MatchString(tag) || zeroPaddedMonthTagRe.MatchString(tag) {
-		return fmt.Errorf("tag %q is not supported — try a tag like %q or \"latest\" in your config file", tag, prevMonthExample())
+		return fmt.Errorf("tag %q is not supported — %s", tag, version.UnsupportedTagMessage())
 	}
 	return nil
 }

internal/version/version.go

@@ -1,7 +1,23 @@
 package version
 
+import (
+	"fmt"
+	"time"
+)
+
 // Set via ldflags at build time. Must be a variable, not a constant,
 // because the linker can only modify variables at link time.
 var version = "dev"
 
 func Version() string { return version }
+
+// UnsupportedTagMessage returns a user-facing error message for an unsupported image tag,
+// e.g. `unsupported image tag — try a tag like "2026.4" or "latest" in your config file`.
+func UnsupportedTagMessage() string {
+	y, m, _ := time.Now().Date()
+	m--
+	if m == 0 {
+		m, y = 12, y-1
+	}
+	return fmt.Sprintf("unsupported image tag — try a tag like %q or \"latest\" in your config file", fmt.Sprintf("%d.%d", y, int(m)))
+}