refactor: route bash app name validation through go

The bash and go validators previously each kept their own copy of the regex, which had to be updated in lockstep. Both bash wrappers now invoke the existing common binary via the same pattern as `verify_app_name`, leaving go as the single source of truth. The legacy `IsValidAppNameOld` rule is also widened to allow underscores again so apps created under the old naming rules can still be looked up through `VerifyAppName`'s either-rule fallback.

plugins/common/common.go

@@ -931,18 +931,18 @@ func IsValidAppName(appName string) error {
 	return errors.New("App name must begin with lowercase alphanumeric character, and may only contain lowercase alphanumerics, dots, and hyphens")
 }
 
-// isValidAppNameOld verifies that the app name matches the old naming restrictions
-func isValidAppNameOld(appName string) error {
+// IsValidAppNameOld verifies that the app name matches the old naming restrictions
+func IsValidAppNameOld(appName string) error {
 	if appName == "" {
 		return errors.New("Please specify an app to run the command on")
 	}
 
-	r, _ := regexp.Compile("^[a-z0-9][a-z0-9.-]*$")
+	r, _ := regexp.Compile("^[a-z0-9][a-z0-9._-]*$")
 	if r.MatchString(appName) {
 		return nil
 	}
 
-	return errors.New("App name must begin with lowercase alphanumeric character, and may only contain lowercase alphanumerics, dots, and hyphens")
+	return errors.New("App name must begin with lowercase alphanumeric character, and may only contain lowercase alphanumerics, dots, hyphens, and underscores")
 }
 
 // AppDoesNotExist wraps error to include the app name
@@ -981,7 +981,7 @@ func VarArgs(arguments []string, skip int) []string {
 // naming conventions exists
 func VerifyAppName(appName string) error {
 	newErr := IsValidAppName(appName)
-	oldErr := isValidAppNameOld(appName)
+	oldErr := IsValidAppNameOld(appName)
 	if newErr != nil && oldErr != nil {
 		return newErr
 	}

plugins/common/common_test.go

@@ -94,6 +94,36 @@ func TestCommonIsValidAppName(t *testing.T) {
 	}
 }
 
+func TestCommonIsValidAppNameOld(t *testing.T) {
+	RegisterTestingT(t)
+	validNames := []string{
+		"myapp",
+		"my-app",
+		"my.app",
+		"my_app",
+		"legacy_app_name",
+		"app_v2",
+	}
+	for _, name := range validNames {
+		Expect(IsValidAppNameOld(name)).To(Succeed(), "expected %q to be a valid app name", name)
+	}
+
+	invalidNames := []string{
+		"app;id",
+		"app$cmd",
+		"app|cat",
+		"app/cmd",
+		"app:cmd",
+		"App",
+		"-app",
+		"_app",
+		"",
+	}
+	for _, name := range invalidNames {
+		Expect(IsValidAppNameOld(name)).To(HaveOccurred(), "expected %q to be rejected", name)
+	}
+}
+
 func TestCommonIsValidAppNameRejectsShellMetacharacters(t *testing.T) {
 	RegisterTestingT(t)
 	invalidNames := []string{

plugins/common/functions

@@ -222,22 +222,14 @@ fn-is-valid-app-name() {
   declare desc="verify that the app name matches naming restrictions"
   local APP="$1"
   [[ -z "$APP" ]] && dokku_log_fail "Please specify an app to run the command on"
-  if [[ "$APP" =~ ^[a-z0-9][a-z0-9.-]*$ ]]; then
-    return 0
-  fi
-
-  return 1
+  "$PLUGIN_CORE_AVAILABLE_PATH/common/common" --quiet is-valid-app-name "$APP"
 }
 
 fn-is-valid-app-name-old() {
   declare desc="verify that the app name matches the old naming restrictions"
   local APP="$1"
   [[ -z "$APP" ]] && dokku_log_fail "Please specify an app to run the command on"
-  if [[ "$APP" =~ ^[a-z0-9][a-z0-9.-]*$ ]]; then
-    return 0
-  fi
-
-  return 1
+  "$PLUGIN_CORE_AVAILABLE_PATH/common/common" --quiet is-valid-app-name-old "$APP"
 }
 
 fn-plugn-trigger-exists() {

plugins/common/src/common/common.go

@@ -86,6 +86,12 @@ func main() {
 		} else {
 			fmt.Print("false")
 		}
+	case "is-valid-app-name":
+		appName := flag.Arg(1)
+		err = common.IsValidAppName(appName)
+	case "is-valid-app-name-old":
+		appName := flag.Arg(1)
+		err = common.IsValidAppNameOld(appName)
 	case "verify-app-name":
 		appName := flag.Arg(1)
 		err = common.VerifyAppName(appName)