Treat an out-of-range navigation timeout as no timeout instead of throwing after undo/redo [patch]

UndoRedo.Test/UndoRedoStackTests.cs

@@ -252,9 +252,9 @@
 		stack.AddCommand(third);
 
 		// startIndex + count overflowed to a negative length before #105
 		CollectionAssert.AreEqual(new[] { second, third }, stack.GetCommandsInRange(1, int.MaxValue).ToList());
 		CollectionAssert.AreEqual(new[] { third }, stack.GetCommandsInRange(2, int.MaxValue).ToList());
 		CollectionAssert.AreEqual(new[] { second }, stack.GetCommandsInRange(1, 1).ToList());
 	}
 
 	private sealed class MockNavigationProvider : INavigationProvider
@@ -844,10 +844,10 @@
 		stack.Execute(new DelegateCommand("C", () => value++, () => value--));
 		stack.Execute(new DelegateCommand("D", () => value++, () => value--)); // Trims A, moving the save point to -1
 		Assert.IsNotNull(heldBoundary);
 		Assert.AreEqual(3, stack.GetCommandsToUndo(heldBoundary).Count(), "The held boundary should resolve to the save point's current position");
 
 		// Act
 		bool result = await stack.UndoToSaveBoundaryAsync(heldBoundary, navigateToLastChange: false).ConfigureAwait(false);
 
 		// Assert
 		Assert.IsTrue(result, "UndoToSaveBoundary should resolve a boundary held across a trim");
@@ -866,14 +866,14 @@
 		stack.Execute(new DelegateCommand("B", () => value++, () => value--));
 		stack.MarkAsSaved();
 		SaveBoundary removedBoundary = stack.SaveBoundaries[0];
 		await stack.UndoAsync(navigateToChange: false).ConfigureAwait(false);
 		await stack.UndoAsync(navigateToChange: false).ConfigureAwait(false);
 		stack.Execute(new DelegateCommand("C", () => value++, () => value--)); // Branches, discarding the save point
 		stack.Execute(new DelegateCommand("D", () => value++, () => value--));
 		stack.Execute(new DelegateCommand("E", () => value++, () => value--));
 
 		// Act
 		bool result = await stack.UndoToSaveBoundaryAsync(removedBoundary, navigateToLastChange: false).ConfigureAwait(false);
 
 		// Assert
 		Assert.IsFalse(result, "UndoToSaveBoundary should reject a boundary that no longer exists");
@@ -1179,6 +1179,35 @@
 		}
 	}
 
+	public static IEnumerable<object[]> NavigationTimeoutsOutsideCancelAfterRange =>
+	[
+		[TimeSpan.MaxValue],
+		[TimeSpan.FromDays(60)],
+		[TimeSpan.FromSeconds(-5)],
+		[TimeSpan.MinValue],
+	];
+
+	[TestMethod]
+	[DynamicData(nameof(NavigationTimeoutsOutsideCancelAfterRange))]
+	public async Task UndoRedoAsync_NavigationTimeoutOutsideCancelAfterRange_AppliesAndNavigatesWithoutThrowing(TimeSpan timeout)
+	{
+		// Arrange
+		UndoRedoService stack = new(new StackManager(), new SaveBoundaryManager(), new CommandMerger(),
+			new UndoRedoOptions(DefaultNavigationTimeout: timeout));
+		MockNavigationProvider navigationProvider = new();
+		stack.SetNavigationProvider(navigationProvider);
+		int value = 0;
+		stack.Execute(new DelegateCommand("Increment", () => value++, () => value--, navigationContext: "editor"));
+
+		// Act & Assert: CancelAfter rejects these values, which surfaced after the change was applied
+		Assert.IsTrue(await stack.UndoAsync().ConfigureAwait(false));
+		Assert.AreEqual(0, value);
+		Assert.AreEqual("editor", navigationProvider.LastNavigatedContext, "Navigation should run with no timeout");
+
+		Assert.IsTrue(await stack.RedoAsync().ConfigureAwait(false));
+		Assert.AreEqual(1, value);
+	}
+
 	private sealed class ThrowingNavigationProvider : INavigationProvider
 	{
 		public Task<bool> NavigateToAsync(string context, CancellationToken cancellationToken = default) =>

UndoRedo/Services/UndoRedoService.cs

@@ -278,6 +278,11 @@
 	private SaveBoundary? FindLiveSaveBoundary(SaveBoundary saveBoundary) =>
 		_saveBoundaryManager.SaveBoundaries.FirstOrDefault(boundary => boundary.IsSameSavePointAs(saveBoundary));
 
+	/// <summary>
+	/// The longest navigation timeout <see cref="CancellationTokenSource.CancelAfter(TimeSpan)"/> accepts on every target framework.
+	/// </summary>
+	private static readonly TimeSpan MaxNavigationTimeout = TimeSpan.FromMilliseconds(int.MaxValue);
+
 	/// <summary>
 	/// Navigates to where a change was made, after the undo or redo has already been applied.
 	/// Navigation is best effort: any failure is swallowed, because an exception here would tell the
@@ -290,12 +295,19 @@
 			return;
 		}
 
-		using CancellationTokenSource cts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
-		cts.CancelAfter(_options.EffectiveNavigationTimeout);
-
 		try
 		{
+			using CancellationTokenSource cts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
+
+			// CancelAfter throws for negative delays and for delays past its limit, which is
+			// int.MaxValue ms on older targets. Treat those as "no timeout" rather than failing here.
+			TimeSpan timeout = _options.EffectiveNavigationTimeout;
+			if (timeout > TimeSpan.Zero && timeout <= MaxNavigationTimeout)
+			{
+				cts.CancelAfter(timeout);
+			}
+
 			await _navigationProvider.NavigateToAsync(navigationContext!, cts.Token).ConfigureAwait(false);
 		}
 #pragma warning disable CA1031 // Do not catch general exception types
 		catch (Exception)