From 1263d4f3d58471b79502b24f8c307f08979853b7 Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Sun, 1 Nov 2026 03:27:55 +0000
Subject: [PATCH] Trim only ASCII white space under AllowLeadingWhite and
 AllowTrailingWhite [patch]
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

TrimAllowedWhite called ReadOnlySpan<char>.TrimStart()/TrimEnd(), which
strip everything char.IsWhiteSpace accepts: NBSP, U+202F, U+3000, NEL,
LS, PS and the other Unicode space separators. NumberStyles allows only
U+0009-U+000D and U+0020, and decimal, double and int reject the rest, so
PreciseNumber accepted input every BCL numeric type refuses (for example a
stray trailing fr-FR group separator, "1 ", under Integer).

The trim now uses that explicit set.

Fixes ktsu-dev/PreciseNumber#181

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017vfJW4JrXevVTQZvqzLBX1
---
 .../PreciseNumberParseCultureTests.cs         | 37 +++++++++++++++++++
 PreciseNumber/PreciseNumber.cs                | 11 +++++-
 2 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/PreciseNumber.Test/PreciseNumberParseCultureTests.cs b/PreciseNumber.Test/PreciseNumberParseCultureTests.cs
index ac429ee..24e238b 100644
--- a/PreciseNumber.Test/PreciseNumberParseCultureTests.cs
+++ b/PreciseNumber.Test/PreciseNumberParseCultureTests.cs
@@ -241,4 +241,41 @@ public void Parse_RejectsATypedSpaceWhenTheStyleDoesNotAllowThousands()
 		Assert.IsFalse(PreciseNumber.TryParse("1 234", NumberStyles.Float, NarrowSpaceGroups, out _));
 		Assert.IsFalse(PreciseNumber.TryParse("1 234", NumberStyles.Float, NoBreakSpaceGroups, out _));
 	}
+
+	[TestMethod]
+	[DataRow("\u00A05", NumberStyles.Integer)]
+	[DataRow("5\u3000", NumberStyles.AllowTrailingWhite)]
+	[DataRow("\u00855", NumberStyles.Float)]
+	[DataRow("5\u2028", NumberStyles.Float)]
+	public void Parse_RejectsNonAsciiWhiteSpaceAroundTheNumber(string input, NumberStyles style)
+	{
+		Assert.IsFalse(decimal.TryParse(input, style, CultureInfo.InvariantCulture, out _), "The BCL should reject this input too.");
+		Assert.IsFalse(PreciseNumber.TryParse(input, style, CultureInfo.InvariantCulture, out _));
+		Assert.ThrowsExactly<FormatException>(() => PreciseNumber.Parse(input, style, CultureInfo.InvariantCulture));
+	}
+
+	[TestMethod]
+	public void Parse_RejectsATrailingNarrowSpaceGroupSeparatorWhenTheStyleDoesNotAllowThousands()
+	{
+		// Shaped like fr-FR, whose group separator is U+202F: a stray one after the digits is not white space.
+		Assert.IsFalse(decimal.TryParse("1\u202F", NumberStyles.Integer, NarrowSpaceGroups, out _), "The BCL should reject this input too.");
+		Assert.IsFalse(PreciseNumber.TryParse("1\u202F", NumberStyles.Integer, NarrowSpaceGroups, out _));
+		Assert.ThrowsExactly<FormatException>(() => PreciseNumber.Parse("1\u202F", NumberStyles.Integer, NarrowSpaceGroups));
+	}
+
+	[TestMethod]
+	[DataRow(" ")]
+	[DataRow("\t")]
+	[DataRow("\r")]
+	[DataRow("\n")]
+	[DataRow("\v")]
+	[DataRow("\f")]
+	public void Parse_TrimsAsciiWhiteSpaceAroundTheNumber(string white)
+	{
+		string input = white + "5" + white;
+
+		Assert.IsTrue(PreciseNumber.TryParse(input, NumberStyles.Integer, CultureInfo.InvariantCulture, out PreciseNumber result));
+		Assert.AreEqual(P("5"), result);
+		Assert.AreEqual(P("5"), PreciseNumber.Parse(input, NumberStyles.Integer, CultureInfo.InvariantCulture));
+	}
 }
diff --git a/PreciseNumber/PreciseNumber.cs b/PreciseNumber/PreciseNumber.cs
index 060127d..927d098 100644
--- a/PreciseNumber/PreciseNumber.cs
+++ b/PreciseNumber/PreciseNumber.cs
@@ -1391,17 +1391,24 @@ private static PreciseNumber FromParsedParts(ReadOnlySpan<char> digits, int deci
 		return new((int)exponent, significand);
 	}
 
+	/// <summary>
+	/// The white space that <see cref="NumberStyles.AllowLeadingWhite"/> and <see cref="NumberStyles.AllowTrailingWhite"/>
+	/// permit: U+0009 to U+000D and U+0020, as for the BCL numeric types. Other Unicode white space, such as a no-break
+	/// space or NEL, is not trimmed.
+	/// </summary>
+	private const string AllowedWhite = " \t\n\v\f\r";
+
 	/// <summary>Trims the leading and trailing white space that <paramref name="style"/> allows.</summary>
 	private static ReadOnlySpan<char> TrimAllowedWhite(ReadOnlySpan<char> s, NumberStyles style)
 	{
 		if (style.HasFlag(NumberStyles.AllowLeadingWhite))
 		{
-			s = s.TrimStart();
+			s = s.TrimStart(AllowedWhite.AsSpan());
 		}
 
 		if (style.HasFlag(NumberStyles.AllowTrailingWhite))
 		{
-			s = s.TrimEnd();
+			s = s.TrimEnd(AllowedWhite.AsSpan());
 		}
 
 		return s;