[patch] Stop [PrefixAndSuffix] letting the prefix and suffix overlap, and reject empty strings

Semantics.Strings/Validation/Attributes/Text/PrefixAndSuffixAttribute.cs

@@ -5,7 +5,8 @@ namespace ktsu.Semantics.Strings;
 using System;
 
 /// <summary>
-/// Validates that the string has both the specified prefix and suffix
+/// Validates that the string has both the specified prefix and suffix, without the two overlapping.
+/// An empty string fails, as it does for <see cref="StartsWithAttribute"/> and <see cref="EndsWithAttribute"/>.
 /// </summary>
 [AttributeUsage(AttributeTargets.Class, AllowMultiple = true, Inherited = true)]
 public sealed class PrefixAndSuffixAttribute(string prefix, string suffix, StringComparison comparison = StringComparison.Ordinal) : NativeSemanticStringValidationAttribute
@@ -55,7 +56,13 @@ protected override ValidationResult ValidateValue(string value)
 		{
 			if (string.IsNullOrEmpty(value))
 			{
-				return ValidationResult.Success();
+				return ValidationResult.Failure($"The value must start with '{_prefix}' and end with '{_suffix}'.");
+			}
+
+			// The prefix and suffix must each have their own characters, so one '"' cannot be both quotes
+			if (value.Length < _prefix.Length + _suffix.Length)
+			{
+				return ValidationResult.Failure($"The value must start with '{_prefix}' and end with '{_suffix}' without the two overlapping.");
 			}
 
 			// Check prefix

Semantics.Test/TextValidationAttributesTests.cs

@@ -196,6 +196,48 @@ public void PrefixAndSuffixAttribute_MissingBoth_ShouldThrow()
 		Assert.ThrowsExactly<ArgumentException>(() => SemanticString<PrefixSuffixTestString>.Create<PrefixSuffixTestString>("middle"));
 	}
 
+	[PrefixAndSuffix("\"", "\"")]
+	[System.Diagnostics.CodeAnalysis.SuppressMessage("Performance", "CA1812:Avoid uninstantiated internal classes", Justification = "Used via generic type references")]
+	private sealed partial record QuotedTestString : SemanticString<QuotedTestString> { }
+
+	[PrefixAndSuffix("ab", "ba")]
+	[System.Diagnostics.CodeAnalysis.SuppressMessage("Performance", "CA1812:Avoid uninstantiated internal classes", Justification = "Used via generic type references")]
+	private sealed partial record AbBaTestString : SemanticString<AbBaTestString> { }
+
+	[TestMethod]
+	public void PrefixAndSuffixAttribute_LoneDelimiterServingAsBoth_ShouldThrow()
+	{
+		Assert.ThrowsExactly<ArgumentException>(() => SemanticString<QuotedTestString>.Create<QuotedTestString>("\""));
+	}
+
+	[TestMethod]
+	public void PrefixAndSuffixAttribute_OverlappingPrefixAndSuffix_ShouldThrow()
+	{
+		Assert.ThrowsExactly<ArgumentException>(() => SemanticString<AbBaTestString>.Create<AbBaTestString>("aba"));
+	}
+
+	[TestMethod]
+	public void PrefixAndSuffixAttribute_EmptyString_ShouldThrow()
+	{
+		Assert.ThrowsExactly<ArgumentException>(() => SemanticString<QuotedTestString>.Create<QuotedTestString>(string.Empty));
+	}
+
+	[TestMethod]
+	[DataRow("\"\"")]
+	[DataRow("\"quoted\"")]
+	public void PrefixAndSuffixAttribute_DelimitersEachPresent_ShouldPass(string value)
+	{
+		QuotedTestString quoted = SemanticString<QuotedTestString>.Create<QuotedTestString>(value);
+		Assert.AreEqual(value, quoted.WeakString);
+	}
+
+	[TestMethod]
+	public void PrefixAndSuffixAttribute_AdjacentPrefixAndSuffix_ShouldPass()
+	{
+		AbBaTestString value = SemanticString<AbBaTestString>.Create<AbBaTestString>("abba");
+		Assert.AreEqual("abba", value.WeakString);
+	}
+
 	// Test multiple validation attributes on empty strings
 	[TestMethod]
 	public void ValidationAttributes_EmptyString_ShouldHandleCorrectly()