Fix 20 more SonarCloud issues; document 8 multi-target false positives

.editorconfig

@@ -382,7 +382,7 @@ dotnet_naming_style.pascal_case.word_separator =
 dotnet_naming_style.pascal_case.capitalization = pascal_case
 
 # C++ files
-[*.cpp,*.h,*.hpp,*.cc,*.hh,*.cxx,*.hxx]
+[*.{cpp,h,hpp,cc,hh,cxx,hxx}]
 indent_style = tab
 
 # Naming convention rules (note: currently need to be ordered from more to less specific)

CLAUDE.md

@@ -98,11 +98,11 @@ All values are stored in SI base units, so operators read `.Value` directly. Sup
 ### File headers
 
 ```csharp
-// Copyright (c) ktsu.dev
-// All rights reserved.
-// Licensed under the MIT license.
+// Copyright (c) 2023-2026 ktsu-dev contributors
 ```
 
+The text comes from `COPYRIGHT.md`; ktsu.Sdk syncs `.editorconfig`'s `file_header_template` from that file on every build, and `IDE0073` enforces it. If `COPYRIGHT.md` changes, update `GeneratorBase.WriteHeaderTo` to match — generator output is committed source, so a drift there shows up as a diff rather than a build error (`.g.cs` is exempt from `IDE0073`). `SourceGeneratorTests` asserts the emitted header, so the drift fails a test instead.
+
 Generator-emitted files additionally carry `// <auto-generated />`.
 
 ### Validation and error handling

Directory.Packages.props

@@ -11,6 +11,7 @@
     <PackageVersion Include="Polyfill" Version="11.2.0" />
     <PackageVersion Include="Microsoft.Bcl.AsyncInterfaces" Version="10.0.11" />
     <PackageVersion Include="System.Memory" Version="4.6.3" />
+    <PackageVersion Include="System.Threading.Tasks.Extensions" Version="4.6.3" />
     <PackageVersion Include="System.Numerics.Vectors" Version="4.6.1" />
     <!-- Source generator packages -->
     <PackageVersion Include="ktsu.CodeBlocker" Version="1.2.8" />

Semantics.Color/Color.Operations.cs

@@ -29,12 +29,15 @@ public double ContrastRatio(Color other)
 	public AccessibilityLevel AccessibilityLevelAgainst(Color background, bool largeText = false)
 	{
 		double contrast = ContrastRatio(background);
-		if (contrast >= (largeText ? 4.5 : 7.0))
+		double enhancedThreshold = largeText ? 4.5 : 7.0;
+		double minimumThreshold = largeText ? 3.0 : 4.5;
+
+		if (contrast >= enhancedThreshold)
 		{
 			return AccessibilityLevel.AAA;
 		}
 
-		return contrast >= (largeText ? 3.0 : 4.5) ? AccessibilityLevel.AA : AccessibilityLevel.Fail;
+		return contrast >= minimumThreshold ? AccessibilityLevel.AA : AccessibilityLevel.Fail;
 	}
 
 	/// <summary>

Semantics.Color/Color.cs

@@ -40,5 +40,5 @@ public readonly partial record struct Color(double R, double G, double B, double
 	/// <returns>A float vector of the linear RGB channels.</returns>
 	public Vector3 ToLinearVector3() => new((float)R, (float)G, (float)B);
 
-	internal static double Clamp01(double value) => value < 0.0 ? 0.0 : value > 1.0 ? 1.0 : value;
+	internal static double Clamp01(double value) => Math.Clamp(value, 0.0, 1.0);
 }

Semantics.Color/Hsl.cs

@@ -146,7 +146,7 @@ public Srgb ToSrgb()
 	/// <returns>The adjusted color.</returns>
 	public Hsl OffsetHue(double degrees) => this with { H = NormalizeHue(H + degrees) };
 
-	private static double Clamp01(double value) => value < 0.0 ? 0.0 : value > 1.0 ? 1.0 : value;
+	private static double Clamp01(double value) => Math.Clamp(value, 0.0, 1.0);
 
 	internal static double NormalizeHue(double h)
 	{

Semantics.Color/Semantics.Color.csproj

@@ -9,6 +9,10 @@
   <ItemGroup>
     <PackageReference Include="Polyfill" PrivateAssets="all" />
     <PackageReference Include="System.Numerics.Vectors" Condition="'$(TargetFramework)' == 'netstandard2.0'" />
+    <!-- Required by KTSU0001 (ktsu.Sdk 2.27.0+): the downlevel targets must reference the packages
+         supplying the framework types they use rather than picking them up transitively. -->
+    <PackageReference Include="System.Memory" Condition="'$(TargetFramework)' == 'netstandard2.0' or '$(TargetFramework)' == 'netstandard2.1'" />
+    <PackageReference Include="System.Threading.Tasks.Extensions" Condition="'$(TargetFramework)' == 'netstandard2.0'" />
   </ItemGroup>
 
 </Project>

Semantics.Music/Semantics.Music.csproj

@@ -8,6 +8,10 @@
 
   <ItemGroup>
     <PackageReference Include="Polyfill" PrivateAssets="all" />
+    <!-- Required by KTSU0001 (ktsu.Sdk 2.27.0+): the downlevel targets must reference the packages
+         supplying the framework types they use rather than picking them up transitively. -->
+    <PackageReference Include="System.Memory" Condition="'$(TargetFramework)' == 'netstandard2.0' or '$(TargetFramework)' == 'netstandard2.1'" />
+    <PackageReference Include="System.Threading.Tasks.Extensions" Condition="'$(TargetFramework)' == 'netstandard2.0'" />
   </ItemGroup>
 
 </Project>

Semantics.Paths/Implementations/RelativeDirectoryPath.cs

@@ -140,16 +140,6 @@ public AbsoluteDirectoryPath AsAbsolute()
 		return AbsoluteDirectoryPath.Create<AbsoluteDirectoryPath>(absolutePath);
 	}
 
-	/// <summary>
-	/// Explicitly implements IRelativePath.AsAbsolute() to return the base AbsolutePath type.
-	/// </summary>
-	/// <returns>An <see cref="AbsolutePath"/> representing this absolute path.</returns>
-	AbsolutePath IRelativePath.AsAbsolute()
-	{
-		string absolutePath = Path.GetFullPath(WeakString);
-		return AbsolutePath.Create<AbsolutePath>(absolutePath);
-	}
-
 	/// <summary>
 	/// Converts this relative directory path to an absolute directory path using the specified base directory.
 	/// </summary>
@@ -167,6 +157,16 @@ public AbsoluteDirectoryPath AsAbsolute(AbsoluteDirectoryPath baseDirectory)
 		return AbsoluteDirectoryPath.Create<AbsoluteDirectoryPath>(absolutePath);
 	}
 
+	/// <summary>
+	/// Explicitly implements IRelativePath.AsAbsolute() to return the base AbsolutePath type.
+	/// </summary>
+	/// <returns>An <see cref="AbsolutePath"/> representing this absolute path.</returns>
+	AbsolutePath IRelativePath.AsAbsolute()
+	{
+		string absolutePath = Path.GetFullPath(WeakString);
+		return AbsolutePath.Create<AbsolutePath>(absolutePath);
+	}
+
 	/// <summary>
 	/// Converts this relative directory path to a relative directory path using the specified base directory.
 	/// Since this is already a relative path, returns itself.

Semantics.Paths/Implementations/RelativeFilePath.cs

@@ -74,16 +74,6 @@ public AbsoluteFilePath AsAbsolute()
 		return AbsoluteFilePath.Create<AbsoluteFilePath>(absolutePath);
 	}
 
-	/// <summary>
-	/// Explicitly implements IRelativePath.AsAbsolute() to return the base AbsolutePath type.
-	/// </summary>
-	/// <returns>An <see cref="AbsolutePath"/> representing this absolute path.</returns>
-	AbsolutePath IRelativePath.AsAbsolute()
-	{
-		string absolutePath = Path.GetFullPath(WeakString);
-		return AbsolutePath.Create<AbsolutePath>(absolutePath);
-	}
-
 	/// <summary>
 	/// Converts this relative file path to an absolute file path using the specified base directory.
 	/// </summary>
@@ -101,6 +91,16 @@ public AbsoluteFilePath AsAbsolute(AbsoluteDirectoryPath baseDirectory)
 		return AbsoluteFilePath.Create<AbsoluteFilePath>(absolutePath);
 	}
 
+	/// <summary>
+	/// Explicitly implements IRelativePath.AsAbsolute() to return the base AbsolutePath type.
+	/// </summary>
+	/// <returns>An <see cref="AbsolutePath"/> representing this absolute path.</returns>
+	AbsolutePath IRelativePath.AsAbsolute()
+	{
+		string absolutePath = Path.GetFullPath(WeakString);
+		return AbsolutePath.Create<AbsolutePath>(absolutePath);
+	}
+
 	/// <summary>
 	/// Converts this relative file path to a relative file path using the specified base directory.
 	/// Since this is already a relative path, returns itself.

Semantics.Paths/Semantics.Paths.csproj

@@ -13,7 +13,10 @@
   <ItemGroup>
     <PackageReference Include="Polyfill" PrivateAssets="all" />
     <PackageReference Include="Microsoft.Bcl.AsyncInterfaces" Condition="'$(TargetFramework)' == 'netstandard2.0'" />
-    <PackageReference Include="System.Memory" Condition="'$(TargetFramework)' == 'netstandard2.0'" />
+    <!-- KTSU0001 (ktsu.Sdk 2.27.0+) requires System.Memory on netstandard2.1 as well, and
+         System.Threading.Tasks.Extensions on netstandard2.0. -->
+    <PackageReference Include="System.Memory" Condition="'$(TargetFramework)' == 'netstandard2.0' or '$(TargetFramework)' == 'netstandard2.1'" />
+    <PackageReference Include="System.Threading.Tasks.Extensions" Condition="'$(TargetFramework)' == 'netstandard2.0'" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Semantics.Strings\Semantics.Strings.csproj" />

Semantics.SourceGenerators/AssemblyInfo.cs

@@ -0,0 +1,5 @@
+// Copyright (c) 2023-2026 ktsu-dev contributors
+
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("ktsu.Semantics.Test")]

Semantics.SourceGenerators/Templates/PropertyTemplate.cs

@@ -7,9 +7,11 @@ namespace Semantics.SourceGenerators.Templates;
 
 internal class PropertyTemplate : MemberTemplate
 {
-	public static Action<CodeBlocker> AutoGet = (sw) => sw.Write("get;");
-	public static Action<CodeBlocker> AutoSet = (sw) => sw.Write("set;");
-	public static Action<CodeBlocker> AutoInit = (sw) => sw.Write("init;");
+	// Compared by reference in WriteTo to detect auto-property shorthand, so these must stay
+	// single fixed instances; readonly enforces that without changing the comparison.
+	public static readonly Action<CodeBlocker> AutoGet = (sw) => sw.Write("get;");
+	public static readonly Action<CodeBlocker> AutoSet = (sw) => sw.Write("set;");
+	public static readonly Action<CodeBlocker> AutoInit = (sw) => sw.Write("init;");
 
 	public Action<CodeBlocker>? GetterFactory { get; set; }
 	public Action<CodeBlocker>? SetterFactory { get; set; }

Semantics.Strings.Identifiers/Semantics.Strings.Identifiers.csproj

@@ -7,7 +7,10 @@
   <ItemGroup>
     <PackageReference Include="Polyfill" PrivateAssets="all" />
     <PackageReference Include="System.Text.Json" />
-    <PackageReference Include="System.Memory" Condition="'$(TargetFramework)' == 'netstandard2.0'" />
+    <!-- KTSU0001 (ktsu.Sdk 2.27.0+) requires System.Memory on netstandard2.1 as well, and
+         System.Threading.Tasks.Extensions on netstandard2.0. -->
+    <PackageReference Include="System.Memory" Condition="'$(TargetFramework)' == 'netstandard2.0' or '$(TargetFramework)' == 'netstandard2.1'" />
+    <PackageReference Include="System.Threading.Tasks.Extensions" Condition="'$(TargetFramework)' == 'netstandard2.0'" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Semantics.Strings\Semantics.Strings.csproj" />

Semantics.Strings/Semantics.Strings.csproj

@@ -15,7 +15,10 @@
     <PackageReference Include="Polyfill" PrivateAssets="all" />
     <PackageReference Include="ktsu.RoundTripStringJsonConverter" />
     <PackageReference Include="System.Text.Json" />
-    <PackageReference Include="System.Memory" Condition="'$(TargetFramework)' == 'netstandard2.0'" />
+    <!-- KTSU0001 (ktsu.Sdk 2.27.0+) requires System.Memory on netstandard2.1 as well, and
+         System.Threading.Tasks.Extensions on netstandard2.0. -->
+    <PackageReference Include="System.Memory" Condition="'$(TargetFramework)' == 'netstandard2.0' or '$(TargetFramework)' == 'netstandard2.1'" />
+    <PackageReference Include="System.Threading.Tasks.Extensions" Condition="'$(TargetFramework)' == 'netstandard2.0'" />
   </ItemGroup>
   <ItemGroup>
     <InternalsVisibleTo Include="ktsu.Semantics.Test" />

Semantics.Strings/Validation/Attributes/Casing/IsKebabCaseAttribute.cs

@@ -27,6 +27,8 @@ public sealed class IsKebabCaseAttribute : NativeSemanticStringValidationAttribu
 	/// </summary>
 	private sealed class KebabCaseValidator : ValidationAdapter
 	{
+		private const string FailureMessage = "The value must be in kebab-case format.";
+
 		/// <summary>
 		/// Validates that a string is in kebab-case.
 		/// </summary>
@@ -40,27 +42,27 @@ protected override ValidationResult ValidateValue(string value)
 			}
 
 			// Cannot start or end with hyphen
-			if (value.StartsWith("-") || value.EndsWith("-"))
+			if (value.StartsWith('-') || value.EndsWith('-'))
 			{
-				return ValidationResult.Failure("The value must be in kebab-case format.");
+				return ValidationResult.Failure(FailureMessage);
 			}
 
 			// Cannot have consecutive hyphens
 			if (value.Contains("--"))
 			{
-				return ValidationResult.Failure("The value must be in kebab-case format.");
+				return ValidationResult.Failure(FailureMessage);
 			}
 
 			// No spaces, underscores, or other separators allowed (except hyphens)
 			if (value.Any(c => char.IsWhiteSpace(c) || c == '_'))
 			{
-				return ValidationResult.Failure("The value must be in kebab-case format.");
+				return ValidationResult.Failure(FailureMessage);
 			}
 
 			// All characters must be lowercase letters, digits, or hyphens
 			if (!value.All(c => char.IsLower(c) || char.IsDigit(c) || c == '-'))
 			{
-				return ValidationResult.Failure("The value must be in kebab-case format.");
+				return ValidationResult.Failure(FailureMessage);
 			}
 
 			return ValidationResult.Success();

Semantics.Strings/Validation/Attributes/Casing/IsMacroCaseAttribute.cs

@@ -28,6 +28,8 @@ public sealed class IsMacroCaseAttribute : NativeSemanticStringValidationAttribu
 	/// </summary>
 	private sealed class MacroCaseValidator : ValidationAdapter
 	{
+		private const string FailureMessage = "The value must be in MACRO_CASE format.";
+
 		/// <summary>
 		/// Validates that a string is in MACRO_CASE.
 		/// </summary>
@@ -41,27 +43,27 @@ protected override ValidationResult ValidateValue(string value)
 			}
 
 			// Cannot start or end with underscore
-			if (value.StartsWith("_") || value.EndsWith("_"))
+			if (value.StartsWith('_') || value.EndsWith('_'))
 			{
-				return ValidationResult.Failure("The value must be in MACRO_CASE format.");
+				return ValidationResult.Failure(FailureMessage);
 			}
 
 			// Cannot have consecutive underscores
 			if (value.Contains("__"))
 			{
-				return ValidationResult.Failure("The value must be in MACRO_CASE format.");
+				return ValidationResult.Failure(FailureMessage);
 			}
 
 			// No spaces, hyphens, or other separators allowed (except underscores)
 			if (value.Any(c => char.IsWhiteSpace(c) || c == '-'))
 			{
-				return ValidationResult.Failure("The value must be in MACRO_CASE format.");
+				return ValidationResult.Failure(FailureMessage);
 			}
 
 			// All characters must be uppercase letters, digits, or underscores
 			if (!value.All(c => char.IsUpper(c) || char.IsDigit(c) || c == '_'))
 			{
-				return ValidationResult.Failure("The value must be in MACRO_CASE format.");
+				return ValidationResult.Failure(FailureMessage);
 			}
 
 			return ValidationResult.Success();

Semantics.Strings/Validation/Attributes/Casing/IsSentenceCaseAttribute.cs

@@ -27,6 +27,8 @@
 	/// </summary>
 	private sealed class SentenceCaseValidator : ValidationAdapter
 	{
+		private const string FailureMessage = "The value must be in sentence case format.";
+
 		/// <summary>
 		/// Validates that a string is in sentence case.
 		/// </summary>
@@ -41,14 +43,14 @@
 
 			// Find the first letter in the string
 			char? firstLetter = value.FirstOrDefault(char.IsLetter);
 			if (firstLetter.HasValue && !char.IsUpper(firstLetter.Value))
 			{
-				return ValidationResult.Failure("The value must be in sentence case format.");
+				return ValidationResult.Failure(FailureMessage);
 			}
 
 			// Check that all other letters after the first are lowercase
 			bool foundFirstLetter = false;
 			foreach (char c in value)
 			{
 				if (char.IsLetter(c))
 				{
@@ -60,7 +62,7 @@
 
 					if (char.IsUpper(c))
 					{
-						return ValidationResult.Failure("The value must be in sentence case format.");
+						return ValidationResult.Failure(FailureMessage);
 					}
 				}
 			}

Semantics.Strings/Validation/Attributes/Casing/IsSnakeCaseAttribute.cs

@@ -27,6 +27,8 @@ public sealed class IsSnakeCaseAttribute : NativeSemanticStringValidationAttribu
 	/// </summary>
 	private sealed class SnakeCaseValidator : ValidationAdapter
 	{
+		private const string FailureMessage = "The value must be in snake_case format.";
+
 		/// <summary>
 		/// Validates that a string is in snake_case.
 		/// </summary>
@@ -40,27 +42,27 @@ protected override ValidationResult ValidateValue(string value)
 			}
 
 			// Cannot start or end with underscore
-			if (value.StartsWith("_") || value.EndsWith("_"))
+			if (value.StartsWith('_') || value.EndsWith('_'))
 			{
-				return ValidationResult.Failure("The value must be in snake_case format.");
+				return ValidationResult.Failure(FailureMessage);
 			}
 
 			// Cannot have consecutive underscores
 			if (value.Contains("__"))
 			{
-				return ValidationResult.Failure("The value must be in snake_case format.");
+				return ValidationResult.Failure(FailureMessage);
 			}
 
 			// No spaces, hyphens, or other separators allowed (except underscores)
 			if (value.Any(c => char.IsWhiteSpace(c) || c == '-'))
 			{
-				return ValidationResult.Failure("The value must be in snake_case format.");
+				return ValidationResult.Failure(FailureMessage);
 			}
 
 			// All characters must be lowercase letters, digits, or underscores
 			if (!value.All(c => char.IsLower(c) || char.IsDigit(c) || c == '_'))
 			{
-				return ValidationResult.Failure("The value must be in snake_case format.");
+				return ValidationResult.Failure(FailureMessage);
 			}
 
 			return ValidationResult.Success();

Semantics.Strings/Validation/Attributes/FirstClassTypes/IsDateTimeAttribute.cs

@@ -17,7 +17,7 @@
 /// Use this attribute only when you specifically need string-based semantic validation.
 /// </summary>
 [AttributeUsage(AttributeTargets.Class, AllowMultiple = false, Inherited = true)]
 [Obsolete("Consider using System.DateTime directly instead of semantic string types. DateTime provides better type safety, performance, built-in comparison operations, and rich API for date/time operations.")]
 public sealed class IsDateTimeAttribute : NativeSemanticStringValidationAttribute
 {
 	/// <summary>
@@ -43,7 +43,9 @@
 				return ValidationResult.Success();
 			}
 
-			bool isValid = DateTime.TryParse(value, out _);
+			// CurrentCulture is stated explicitly rather than switching to InvariantCulture: it is
+			// what the provider-less overload already used, so validation behaviour is unchanged.
+			bool isValid = DateTime.TryParse(value, System.Globalization.CultureInfo.CurrentCulture, System.Globalization.DateTimeStyles.None, out _);
 			return isValid
 				? ValidationResult.Success()
 				: ValidationResult.Failure("The value must be a valid DateTime.");

Semantics.Strings/Validation/Attributes/FirstClassTypes/IsTimeSpanAttribute.cs

@@ -17,7 +17,7 @@
 /// Use this attribute only when you specifically need string-based semantic validation.
 /// </summary>
 [AttributeUsage(AttributeTargets.Class, AllowMultiple = false, Inherited = true)]
 [Obsolete("Consider using System.TimeSpan directly instead of semantic string types. TimeSpan provides better type safety, performance, built-in comparison operations, and rich API for time operations.")]
 public sealed class IsTimeSpanAttribute : NativeSemanticStringValidationAttribute
 {
 	/// <summary>
@@ -43,7 +43,9 @@
 				return ValidationResult.Success();
 			}
 
-			bool isValid = TimeSpan.TryParse(value, out _);
+			// CurrentCulture is stated explicitly rather than switching to InvariantCulture: it is
+			// what the provider-less overload already used, so validation behaviour is unchanged.
+			bool isValid = TimeSpan.TryParse(value, System.Globalization.CultureInfo.CurrentCulture, out _);
 			return isValid
 				? ValidationResult.Success()
 				: ValidationResult.Failure("The value must be a valid TimeSpan.");