From 755c2f069d07b8a35e66d374a3180bc2d874e846 Mon Sep 17 00:00:00 2001
From: "Steven R. Loomis" <srl295@gmail.com>
Date: Fri, 29 Mar 2024 08:52:21 -0500
Subject: [PATCH] CLDR-17467 kbd: disallow empty match

---
 docs/ldml/tr35-keyboards.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/docs/ldml/tr35-keyboards.md b/docs/ldml/tr35-keyboards.md
index 4c559eb1499..13fef4b59bf 100644
--- a/docs/ldml/tr35-keyboards.md
+++ b/docs/ldml/tr35-keyboards.md
@@ -2300,6 +2300,10 @@ The following are additions to standard Regex syntax.
 
 #### Disallowed Regex Features
 
+- **Matching an empty string**
+
+    Transforms may not match an empty string. For example, `<transform from=""/>` or `<transform from="X{0,1}"/>` are not allowed and must be flagged as an error to keyboard authors.
+
 - **Unicode properties**
 
     `\p{property}` `\P{property}`