From 52c33818fabc09440ab500ba3786e2f7e22ed5f4 Mon Sep 17 00:00:00 2001
From: Besser Sehen Landshut <hallo@bessersehen.la>
Date: Thu, 20 Aug 2026 14:25:30 +0200
Subject: [PATCH] fix: allow non-Latin characters in display names
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Registering with a display name such as "Jürgen Müller" fails with
"Erlaubt sind a-z, 0-9, - . _". Two checks reject it, both using \w,
which means [A-Za-z0-9_] in JavaScript as well as in Go:

  ui/.../SignUpForm/index.tsx   const nameRegex = /^[\w.-\s]{2,30}$/
  pkg/checker/username.go       usernameReg = `^[\w.\- ]{2,30}$`

This affects every language except English. The second check is not
really about the display name: MakeUsername derives the username from
it, and the username ends up in a profile URL, so it is restricted on
purpose. The restriction is simply applied one step too early.

Answer already solves this elsewhere. Question URLs are transliterated
in pkg/htmltext via unidecode.Unidecode, and MakeUsername already
handles Chinese through pinyin. This change carries that idea through:

  - transliterate the display name before deriving the username, using
    the dependency the project already ships (go-unidecode)
  - drop what transliteration may leave behind — "Ольга" becomes
    "Ol'ga", and an apostrophe is not a valid username character
  - widen the front-end check to Unicode letters and digits

The display name keeps its original spelling; only the derived username
is transliterated:

  Jürgen Müller  ->  jurgen-muller
  José García    ->  jose-garcia
  Ольга          ->  olga
  Ελένη          ->  elene
  Straße         ->  strasse

Chinese input is unaffected — pinyin still runs first.
---
 internal/service/user_common/user.go            | 17 +++++++++++++++++
 .../Register/components/SignUpForm/index.tsx    |  2 +-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/internal/service/user_common/user.go b/internal/service/user_common/user.go
index 2e777f14c..b2c7d9c6d 100644
--- a/internal/service/user_common/user.go
+++ b/internal/service/user_common/user.go
@@ -21,6 +21,7 @@ package usercommon
 
 import (
 	"context"
+	"regexp"
 	"strings"
 
 	"github.com/apache/answer/internal/base/constant"
@@ -35,6 +36,7 @@ import (
 	"github.com/apache/answer/pkg/checker"
 	"github.com/apache/answer/pkg/random"
 	"github.com/mozillazg/go-pinyin"
+	"github.com/mozillazg/go-unidecode"
 	"github.com/segmentfault/pacman/errors"
 	"github.com/segmentfault/pacman/log"
 )
@@ -190,6 +192,10 @@ func (us *UserCommon) FormatUserBasicInfo(ctx context.Context, userInfo *entity.
 	return userBasicInfo
 }
 
+// usernameDisallowed matches everything checker.IsInvalidUsername rejects.
+// Kept in sync with pkg/checker/username.go.
+var usernameDisallowed = regexp.MustCompile(`[^\w.\- ]`)
+
 // MakeUsername
 // Generate a unique Username based on the displayName
 func (us *UserCommon) MakeUsername(ctx context.Context, displayName string) (username string, err error) {
@@ -198,6 +204,17 @@ func (us *UserCommon) MakeUsername(ctx context.Context, displayName string) (use
 		displayName = strings.Join(pinyin.LazyConvert(displayName, nil), "")
 	}
 
+	// Other non-Latin characters, such as German umlauts or accented
+	// letters, are transliterated the same way question URLs are (see
+	// pkg/htmltext). Without this, a display name like "Jürgen Müller"
+	// would produce an invalid username and registration would fail.
+	displayName = unidecode.Unidecode(displayName)
+
+	// Transliteration can emit characters a username may not contain:
+	// "Ольга" becomes "Ol'ga", for example. Drop those, so the result
+	// still satisfies checker.IsInvalidUsername below.
+	displayName = usernameDisallowed.ReplaceAllString(displayName, "")
+
 	username = strings.ReplaceAll(displayName, " ", "-")
 	username = strings.ToLower(username)
 	suffix := ""
diff --git a/ui/src/pages/Users/Register/components/SignUpForm/index.tsx b/ui/src/pages/Users/Register/components/SignUpForm/index.tsx
index 8dc30b965..c01da32c5 100644
--- a/ui/src/pages/Users/Register/components/SignUpForm/index.tsx
+++ b/ui/src/pages/Users/Register/components/SignUpForm/index.tsx
@@ -57,7 +57,7 @@ const Index: React.FC<Props> = ({ callback }) => {
   });
 
   const emailCaptcha = useCaptchaPlugin('email');
-  const nameRegex = /^[\w.-\s]{2,30}$/;
+  const nameRegex = /^[\p{L}\p{N}._\s-]{2,30}$/u;
 
   const handleChange = (params: FormDataType) => {
     setFormData({ ...formData, ...params });