Fix popping with ".." and QueryString (#13507)

* Fix popping with ".." and QueryString

* - add additional Unit Tests

Author: PureWeen

Xamarin.Forms.Core.UnitTests/ShellModalTests.cs

@@ -316,6 +316,24 @@ public async Task BasicQueryStringTest()
 			Assert.AreEqual("1234", testPage.SomeQueryParameter);
 		}
 
+
+		[TestCase("..")]
+		[TestCase("../")]
+		public async Task PoppingWithQueryString(string input)
+		{
+			Routing.RegisterRoute("details", typeof(ShellTestPage));
+			var shell = new TestShell(CreateShellItem());
+
+			await shell.GoToAsync("details");
+			await shell.GoToAsync("ModalTestPage");
+
+			await shell.GoToAsync(new ShellNavigationState($"{input}?{nameof(ShellTestPage.SomeQueryParameter)}=1234"));
+			shell.AssertCurrentStateEquals($"//{shell.CurrentItem.CurrentItem.CurrentItem.Route}/details");
+
+			var testPage = shell.CurrentPage as ShellTestPage;
+			Assert.AreEqual("1234", testPage.SomeQueryParameter);
+		}
+
 		[Test]
 		public async Task NavigatingAndNavigatedFiresForShellModal()
 		{

Xamarin.Forms.Core.UnitTests/ShellTestBase.cs

@@ -341,6 +341,11 @@ public void RegisterPage(string route, ContentPage contentPage)
 				Routing.RegisterRoute(route, new ConcretePageFactory(contentPage));
 			}
 
+			public void AssertCurrentStateEquals(string expectedState)
+			{
+				Assert.AreEqual(expectedState, CurrentState.Location.ToString());
+			}
+
 			public class ConcretePageFactory : RouteFactory
 			{
 				ContentPage _contentPage;

Xamarin.Forms.Core/Shell/ShellUriHandler.cs

@@ -17,12 +17,15 @@ internal static Uri FormatUri(Uri path, Shell shell)
 		{
 			if (path.OriginalString.StartsWith("..") && shell?.CurrentState != null)
 			{
+				var pathAndQueryString = path.OriginalString.Split(new[] { '?' }, 2);
+				string pathPart = pathAndQueryString[0];
+				string queryString = (pathAndQueryString.Length > 1) ? $"?{pathAndQueryString[1]}" : String.Empty;
+
 				var pages = ShellNavigationManager.BuildFlattenedNavigationStack(shell);
-				var currentState = shell.CurrentState.FullLocation.OriginalString;
 
 				List<string> restOfPath = new List<string>();
 				bool dotsAllParsed = false;
-				foreach (var p in path.OriginalString.Split(_pathSeparators))
+				foreach (var p in pathPart.Split(_pathSeparators))
 				{
 					if (p != ".." || dotsAllParsed)
 					{
@@ -54,7 +57,7 @@ internal static Uri FormatUri(Uri path, Shell shell)
 				restOfPath.Insert(0, shell.CurrentItem.CurrentItem.CurrentItem.Route);
 				restOfPath.Insert(0, shell.CurrentItem.CurrentItem.Route);
 				restOfPath.Insert(0, shell.CurrentItem.Route);
-				var result = String.Join(_pathSeparator, restOfPath);
+				var result = $"{String.Join(_pathSeparator, restOfPath)}{queryString}";
 				var returnValue = ConvertToStandardFormat("scheme", "host", null, new Uri(result, UriKind.Relative));
 				return new Uri(FormatUri(returnValue.PathAndQuery), UriKind.Relative);
 			}