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[patch] Title-case [IsTitleCase] values with invariant rules, not the thread culture #403

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Merged
matt-edmondson merged 1 commit into from
Oct 9, 2026
Merged

[patch] Title-case [IsTitleCase] values with invariant rules, not the thread culture #403

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5 changes: 3 additions & 2 deletions Semantics.Strings/Validation/Attributes/Casing/IsTitleCaseAttribute.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -39,8 +39,9 @@ protected override ValidationResult ValidateValue(string value)
return ValidationResult.Success();
}

// Use TextInfo.ToTitleCase and compare with original
string titleCase = CultureInfo.CurrentCulture.TextInfo.ToTitleCase(value.ToLowerInvariant());
// Title-case with invariant rules, as the lowercasing does, so the result does not depend
// on the thread culture (Turkish title-cases "istanbul" to "İstanbul")
string titleCase = CultureInfo.InvariantCulture.TextInfo.ToTitleCase(value.ToLowerInvariant());
bool isValid = string.Equals(value, titleCase, StringComparison.Ordinal);
return isValid
? ValidationResult.Success()
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21 changes: 21 additions & 0 deletions Semantics.Test/CasingValidatorsTests.cs
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Expand Up @@ -2,6 +2,7 @@

namespace ktsu.Semantics.Test;

using System.Globalization;
using ktsu.Semantics.Strings;
using Microsoft.VisualStudio.TestTools.UnitTesting;

Expand Down Expand Up @@ -66,6 +67,26 @@ public void TitleCase_Valid_Invalid_Empty()
Assert.AreEqual("", empty.WeakString);
}

[TestMethod]
[DataRow("en-US")]
[DataRow("tr-TR")]
[DataRow("az-Latn-AZ")]
public void TitleCase_DoesNotDependOnThreadCulture(string cultureName)
{
CultureInfo original = CultureInfo.CurrentCulture;
try
{
CultureInfo.CurrentCulture = new CultureInfo(cultureName);
TitleCaseString valid = SemanticString<TitleCaseString>.Create<TitleCaseString>("Istanbul Is Lovely");
Assert.AreEqual("Istanbul Is Lovely", valid.WeakString);
Assert.ThrowsExactly<ArgumentException>(() => SemanticString<TitleCaseString>.Create<TitleCaseString>("istanbul"));
}
finally
{
CultureInfo.CurrentCulture = original;
}
}

[TestMethod]
public void SentenceCase_Valid_Invalid_Empty()
{
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7 changes: 7 additions & 0 deletions Semantics.Test/Semantics.Test.csproj
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Expand Up @@ -10,6 +10,13 @@
<TestingPlatformShowTestsFailure>true</TestingPlatformShowTestsFailure>
<TestingPlatformShowTestsFailureDetails>true</TestingPlatformShowTestsFailureDetails>
<NoWarn>$(NoWarn);MSTEST0032</NoWarn>
<!-- ktsu.Sdk turns on invariant globalization, where every culture but the invariant one fails
to construct. The libraries are consumed by projects that do not, so the tests that prove a
validator ignores the thread culture (tr-TR, az) need real cultures to set. With it off, the
analyzers start flagging culture-sensitive calls (CA1304, CA1307); SemanticStringTests makes
those calls on purpose, to cover SemanticString's own culture-default overloads. -->
<InvariantGlobalization>false</InvariantGlobalization>
<NoWarn>$(NoWarn);CA1304;CA1307</NoWarn>
</PropertyGroup>

<ItemGroup>
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