Reject blank input in ParsePhrase with its own argument name

Keybinding.Test/ParsePhraseEmptyInputTests.cs

@@ -0,0 +1,21 @@
+// Copyright (c) 2023-2026 ktsu-dev contributors
+
+namespace ktsu.Keybinding.Test;
+
+using ktsu.Keybinding.Core.Services;
+
+[TestClass]
+public class ParsePhraseEmptyInputTests
+{
+	[TestMethod]
+	[DataRow("")]
+	[DataRow("   ")]
+	[DataRow(null)]
+	public void ParsePhrase_BlankInput_ThrowsNamingPhraseString(string? phraseString)
+	{
+		KeybindingService service = new(new CommandRegistry(), new ProfileManager());
+
+		ArgumentException ex = Assert.ThrowsExactly<ArgumentException>(() => service.ParsePhrase(phraseString!));
+		Assert.AreEqual("phraseString", ex.ParamName, "The exception should name the caller's argument, not the Phrase constructor's.");
+	}
+}

Keybinding/Contracts/IKeybindingService.cs

@@ -128,6 +128,7 @@ public interface IKeybindingService
 	/// </summary>
 	/// <param name="phraseString">The phrase string to parse</param>
 	/// <returns>Phrase containing the sequence of chords</returns>
+	/// <exception cref="ArgumentException">Thrown when phraseString is null or whitespace</exception>
 	public Phrase ParsePhrase(string phraseString);
 
 	/// <summary>

Keybinding/Services/KeybindingService.cs

@@ -36,7 +36,7 @@
 			throw new ArgumentException("Profile ID cannot be null or whitespace", nameof(id));
 		}
 
 		ArgumentException.ThrowIfNullOrWhiteSpace(name, nameof(name));
 
 		return _profileManager.CreateProfile(id, name, description);
 	}
@@ -179,7 +179,7 @@
 	{
 		if (string.IsNullOrWhiteSpace(phraseString))
 		{
-			return new Phrase([]);
+			throw new ArgumentException("Phrase string cannot be null or whitespace", nameof(phraseString));
 		}
 
 		// Split by comma to get individual chord strings