Trim only ASCII white space under AllowLeadingWhite and AllowTrailingWhite [patch]

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));
+	}
 }

PreciseNumber/PreciseNumber.cs

@@ -744,7 +744,7 @@
 	/// A fixed precision such as <c>E15</c> rounds values that need 17 digits, which turns
 	/// <see cref="double.MaxValue"/> into a number that converts back to infinity.
 	/// </remarks>
 	internal static string GetStringFormatForFloatType<TFloat>()
 		where TFloat : INumber<TFloat>
 		=> "R";
 
@@ -1205,7 +1205,7 @@
 	public static PreciseNumber MinMagnitudeNumber(PreciseNumber x, PreciseNumber y) => MinMagnitude(x, y);
 
 	/// <inheritdoc/>
 	public static PreciseNumber Parse(ReadOnlySpan<char> s, NumberStyles style, IFormatProvider? provider)
 	{
 		// Read the separator and signs from the same culture TryFormat writes them with, so that
 		// Parse(x.ToString(p), p) round-trips for every provider.
@@ -1263,14 +1263,14 @@
 					}
 
 					hasDecimal = true;
 					i += decimalSeparator.Length - 1;
 					continue;
 				}
 
 				// Group separators may only sit between integral digits.
 				if (allowThousands && !hasDecimal && digitCount > 0 && StartsWithSeparator(s[i..], groupSeparator))
 				{
 					i += groupSeparator.Length - 1;
 					continue;
 				}
 
@@ -1391,17 +1391,24 @@
 		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;