dotnet/runtime

Regex incorrectly identify surrogate pair unicode category

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#16,922 opened on Apr 7, 2016

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 (41 comments) (2 reactions) (0 assignees)C# (5,445 forks)batch import
area-System.Text.RegularExpressionsbughelp wanted

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Description

This defect makes regex useless when you need to match string using unicode categories and string could contain surrogate pairs:

        [Test]
        public void ClassifySurrogates_Test()
        {
            var value = "𦕒";
            var regexLetters = new Regex(@"^\p{Lo}$");

            var regexSurrogates = new Regex(@"^\p{Cs}{2}$");

            Assert.AreEqual(UnicodeCategory.OtherLetter, char.GetUnicodeCategory(value, 0));
            Assert.AreEqual(UnicodeCategory.OtherLetter, CharUnicodeInfo.GetUnicodeCategory(value, 0));
            Assert.True(regexSurrogates.IsMatch(value));

            // Fails here
            Assert.True(regexLetters.IsMatch(value));
        }

Contributor guide

Research direction
Examine the regex engine's handling of Unicode categories for surrogate pairs. Trace the code path for \p{Lo} and ensure it correctly matches characters above U+FFFF.
Tech stack
csharp
Domain
backend
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
GitC#RegexUnicode
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70