Java Regex - Allow all regular Unicode characters for names but not obscure variants

Question

In java (v11) I would like to allow all characters in any language for choosing a username, so ASCII, Latin, Greek, Chinese and so on.

We tried the pattern \p{IsAlphabetic}.

But with this pattern names like "𝕮𝖍𝖗𝖎𝖘" are allowed. I don't want to let people to style their name with such unicode characters. I want him to enter "Chris" and not "𝕮𝖍𝖗𝖎𝖘"

It should be allowed to name yourself "尤雨溪", "Linus" or "Gödel".

How to achieve a proper Regex not allowing strange styles in names?

Answer 1

Here is a regular expression that allows Latin, Han Chinese, Greek, Russian Cyrillic. It can be completed with more Unicode Scripts.

^(\p{sc=Han}+|\p{sc=Latin}+|\p{sc=Greek}+|\p{sc=Cyrillic})$

Demo here: https://regex101.com/r/yCt5xT/1

Here is the full list of Unicode Scripts that can be used: https://www.regular-expressions.info/unicode.html

\p{Common}
\p{Arabic}
\p{Armenian}
\p{Bengali}
\p{Bopomofo}
\p{Braille}
\p{Buhid}
\p{Canadian_Aboriginal}
\p{Cherokee}
\p{Cyrillic}
\p{Devanagari}
\p{Ethiopic}
\p{Georgian}
\p{Greek}
\p{Gujarati}
\p{Gurmukhi}
\p{Han}
\p{Hangul}
\p{Hanunoo}
\p{Hebrew}
\p{Hiragana}
\p{Inherited}
\p{Kannada}
\p{Katakana}
\p{Khmer}
\p{Lao}
\p{Latin}
\p{Limbu}
\p{Malayalam}
\p{Mongolian}
\p{Myanmar}
\p{Ogham}
\p{Oriya}
\p{Runic}
\p{Sinhala}
\p{Syriac}
\p{Tagalog}
\p{Tagbanwa}
\p{TaiLe}
\p{Tamil}
\p{Telugu}
\p{Thaana}
\p{Thai}
\p{Tibetan}
\p{Yi} 

Answer 2

The challenge is that is composed of surrogate pairs, which the regex engine interprets as code points, not chars.

The solution is to match any letter using \p{L}, but exclude code points of high surrogates on up:

"[\\p{L}&&[^\\x{0d000}-\\x{10ffff}]]+"

---

Trying to exclude the unicode characters

"[\\p{L}&&[^\ud000-\uffff]]+" // doesn't work

doesn't work, because the surrogate pairs are merged into a single code point.

---

Test code:

String[] names = {"尤雨溪", "Linus", "Gödel", "\uD835\uDD6E\uD835\uDD8D\uD835\uDD97\uD835\uDD8E\uD835\uDD98"};

for (String name : names) {
    System.out.println(name + ": " + name.matches("[\\p{L}&&[^\\x{0d000}-\\x{10ffff}]]+"));
}

Output:

尤雨溪: true
Linus: true
Gödel: true
𝕮𝖍𝖗𝖎𝖘: false