Run the menu's verbs on the path given with -p instead of asking again [patch]

FileDeduplicator.Test/MenuTests.cs

@@ -61,6 +61,31 @@ public void MenuRunsTheChosenVerbAndOffersTheMenuAgain()
 		Assert.AreEqual(2, output.Split("0. Exit").Length - 1, "The menu was not offered again after the verb ran.");
 	}
 
+	/// <summary>
+	/// <c>FileDeduplicator -p dir</c> with no verb lands on the menu, and the verb chosen from it
+	/// works on that directory rather than asking for a path again -- every time it is chosen.
+	/// </summary>
+	[TestMethod]
+	public void MenuHandsItsPathToTheChosenVerb()
+	{
+		// Arrange
+		using TempTree tree = new();
+		_ = tree.Write("a.txt", "alpha");
+		_ = tree.Write("aa.txt", "alpha");
+		Type[] menuVerbs = [.. Program.Verbs.Where(t => t != typeof(Menu))];
+		int scan = Array.IndexOf(menuVerbs, typeof(Scan)) + 1;
+		Assert.IsGreaterThan(0, scan, "Scan is not on the menu.");
+
+		// Act -- no path on stdin: the only path is the one the menu was given
+		string output = ConsoleCapture.Run(new Menu { PathString = tree.Root.WeakString }, $"{scan}\n{scan}\n0\n", out int exitCode);
+
+		// Assert
+		Assert.AreEqual(0, exitCode, output);
+		Assert.DoesNotContain("Enter the path", output, $"The menu dropped its -p path and asked again. Output was:\n{output}");
+		Assert.AreEqual(2, output.Split($"Scanning: {tree.Root}").Length - 1, $"Scan did not work on the menu's path both times. Output was:\n{output}");
+		Assert.AreEqual(2, output.Split("Found 1 group(s) of duplicate files").Length - 1, output);
+	}
+
 	[TestMethod]
 	public void MenuRejectsAChoiceThatIsNotOnIt()
 	{

FileDeduplicator/Verbs/Menu.cs

@@ -73,7 +73,7 @@ internal ControlRepeater BuildScrollMenu(out ExitCommand exit)
 
 	private void RunNumberedMenu()
 	{
-		BaseVerb[] verbs = [.. MenuVerbs.Select(CreateVerb)];
+		ICommand[] verbs = [.. MenuVerbs.Select(CreateCommand)];
 		string[] texts = [.. MenuVerbs.Select(DescribeVerb)];
 
 		while (true)
@@ -105,11 +105,23 @@ private void RunNumberedMenu()
 		}
 	}
 
-	private static BaseVerb CreateVerb(Type verbType)
+	/// <summary>
+	/// Creates the command a menu entry runs: the verb, handed the menu's own <c>-p</c> path each
+	/// time it is chosen.
+	/// </summary>
+	/// <remarks>
+	/// The menu is the default verb, so <c>FileDeduplicator -p dir</c> lands here with the path set.
+	/// Dropping it would ask for the path again and invite a different one into a flow that can end
+	/// in deletion. It is re-applied on every run because <see cref="BaseVerb{T}.Run()"/> clears the
+	/// verb's path when it finishes.
+	/// </remarks>
+	/// <param name="verbType">The verb to run.</param>
+	/// <returns>The command that runs it.</returns>
+	private PresetPathCommand CreateCommand(Type verbType)
 	{
 		BaseVerb? verb = Activator.CreateInstance(verbType) as BaseVerb;
 		Debug.Assert(verb != null);
-		return verb;
+		return new(verb, () => PathString);
 	}
 
 	private static string DescribeVerb(Type verbType)
@@ -119,13 +131,29 @@ private static string DescribeVerb(Type verbType)
 		return string.IsNullOrEmpty(helpText) ? name : $"{name} - {helpText}";
 	}
 
-	private static LabelMenuItem CreateMenuItem(Type verbType) => new()
+	private LabelMenuItem CreateMenuItem(Type verbType) => new()
 	{
 		Text = DescribeVerb(verbType),
-		Command = CreateVerb(verbType),
+		Command = CreateCommand(verbType),
 		IsEnabled = true,
 	};
 
+	/// <summary>
+	/// Runs a verb with the path the menu was given, or with none so that the verb asks for one.
+	/// </summary>
+	/// <param name="verb">The verb to run.</param>
+	/// <param name="path">Reads the menu's path at the moment the verb runs.</param>
+	private sealed class PresetPathCommand(BaseVerb verb, Func<string?> path) : ICommand
+	{
+		public bool IsActive => verb.IsActive;
+
+		public void Execute()
+		{
+			verb.PathString = path();
+			verb.Execute();
+		}
+	}
+
 	/// <summary>
 	/// The menu item that leaves the menu, which otherwise could only be left with Ctrl+C.
 	/// </summary>