This is an automated email from the ASF dual-hosted git repository.
lukaszlenart pushed a commit to branch main
in repository https://gitbox.apache.org/repos/asf/struts-site.git
The following commit(s) were added to refs/heads/main by this push:
new ee7a04594 WW-5703 docs: describe the whitespace-only alternative in
derived HTML5 patterns (#335)
ee7a04594 is described below
commit ee7a045946fad17e7cce73b0db8790968f089f73
Author: Lukasz Lenart <[email protected]>
AuthorDate: Mon Sep 14 12:49:10 2026 +0200
WW-5703 docs: describe the whitespace-only alternative in derived HTML5
patterns (#335)
Companion to apache/struts#1938.
Co-authored-by: Claude Opus 5 (1M context) <[email protected]>
---
source/core-developers/client-side-validation.md | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/source/core-developers/client-side-validation.md
b/source/core-developers/client-side-validation.md
index 1b7157d27..381827a8c 100644
--- a/source/core-developers/client-side-validation.md
+++ b/source/core-developers/client-side-validation.md
@@ -116,6 +116,14 @@ whitespace set, so a pattern like `^\S+$` would accept a
value containing a non-
and reject it in the browser. Any regex using a construct outside this
allowlist simply gets no `pattern`
attribute at all — it is never rejected loudly, it just quietly doesn't get a
client-side check.
+**A `pattern` may carry a whitespace-only alternative.** `RegexFieldValidator`
skips any value that trims to
+the empty string *before* it consults its own `trim` param — the check is
`value.trim().isEmpty()` — so even
+with `trim="false"` a single space passes the server. The browser, however,
skips `pattern` only for the
+empty string and would block that space. Unless the field also carries a
`requiredstring` validator that
+trims (its default), which rejects blank input server-side, the emitted
pattern is therefore
+`(?:<regex>)|[\x00-\x20]*`: the original regex, or a value made only of the
characters `String.trim()`
+strips. With a trimming `requiredstring` present, the bare regex is emitted.
+
### `data-msg-*` attributes
Every validator carrying a message — even one that emits no HTML constraint
attribute at all — adds a
