Fixes crash when GC runs in the middle of a navigation

Samples/Nalu.Maui.Sample/Pages/OnePage.xaml

@@ -2,6 +2,8 @@
 <ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
              xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
              xmlns:pageModels="clr-namespace:Nalu.Maui.Sample.PageModels"
+             xmlns:nalu="https://nalu-development.github.com/nalu/navigation"
+             xmlns:pages="clr-namespace:Nalu.Maui.Sample.Pages"
              x:Class="Nalu.Maui.Sample.Pages.OnePage"
              x:DataType="pageModels:OnePageModel"
              Title="Page One"
@@ -26,6 +28,15 @@
             <Button Command="{Binding PushThreeCommand}"
                     Text="Push Three"
                     HorizontalOptions="Center" />
+
+            <Button Command="{nalu:NavigateCommand}"
+                    Text="Push Six Via XAML">
+                <Button.CommandParameter>
+                    <nalu:RelativeNavigation>
+                        <nalu:NavigationSegment Type="pages:SixPage" />
+                    </nalu:RelativeNavigation>
+                </Button.CommandParameter>
+            </Button>
         </VerticalStackLayout>
     </ScrollView>
 

Samples/Nalu.Maui.Sample/Pages/SixPage.xaml

@@ -3,6 +3,8 @@
 <ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
              xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
              xmlns:pageModels="clr-namespace:Nalu.Maui.Sample.PageModels"
+             xmlns:nalu="https://nalu-development.github.com/nalu/navigation"
+             xmlns:pages="clr-namespace:Nalu.Maui.Sample.Pages"
              x:Class="Nalu.Maui.Sample.Pages.SixPage"
              x:DataType="pageModels:SixPageModel"
              Title="Page Six"
@@ -19,6 +21,14 @@
                 </Label.FormattedText>
             </Label>
             <Button Text="One" Command="{Binding GoToOneCommand}" />
+            <Button Command="{nalu:NavigateCommand}"
+                    Text="Push Six Via XAML">
+                <Button.CommandParameter>
+                    <nalu:RelativeNavigation>
+                        <nalu:NavigationSegment Type="pages:SixPage" />
+                    </nalu:RelativeNavigation>
+                </Button.CommandParameter>
+            </Button>
         </VerticalStackLayout>
     </ContentPage.Content>
 </ContentPage>

Samples/Nalu.Maui.Sample/Pages/ThreePage.xaml

@@ -3,6 +3,8 @@
 <ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
              xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
              xmlns:pageModels="clr-namespace:Nalu.Maui.Sample.PageModels"
+             xmlns:nalu="https://nalu-development.github.com/nalu/navigation"
+             xmlns:pages="clr-namespace:Nalu.Maui.Sample.Pages"
              x:Class="Nalu.Maui.Sample.Pages.ThreePage"
              x:DataType="pageModels:ThreePageModel"
              Title="Page Three"
@@ -21,6 +23,15 @@
                     Text="Push Four"/>
             <Button Command="{Binding ReplaceSixCommand}"
                     Text="Replace with six"/>
+
+            <Button Command="{nalu:NavigateCommand}"
+                    Text="Push Six Via XAML">
+                <Button.CommandParameter>
+                    <nalu:RelativeNavigation>
+                        <nalu:NavigationSegment Type="pages:SixPage" />
+                    </nalu:RelativeNavigation>
+                </Button.CommandParameter>
+            </Button>
         </VerticalStackLayout>
     </ContentPage.Content>
 </ContentPage>

Source/Nalu.Maui.Navigation/Internals/FixedRouteFactory.cs

@@ -2,16 +2,26 @@ namespace Nalu;
 
 internal class FixedRouteFactory : RouteFactory
 {
-    private readonly WeakReference<Page> _weakPage;
+    private Page? _page;
 
 #pragma warning disable IDE0290
     public FixedRouteFactory(Page page)
 #pragma warning restore IDE0290
     {
-        _weakPage = new WeakReference<Page>(page);
+        _page = page;
     }
 
-    public override Element GetOrCreate() => _weakPage.TryGetTarget(out var page) ? page : throw new InvalidOperationException("Page has been collected");
+    public override Element GetOrCreate()
+    {
+        var page = _page;
+        if (page is not null)
+        {
+            _page = null;
+            return page;
+        }
+
+        throw new InvalidOperationException("Page has already been created.");
+    }
 
     public override Element GetOrCreate(IServiceProvider services) => GetOrCreate();
 }

Source/Nalu.Maui.Navigation/Internals/PageNavigationContext.cs

@@ -5,6 +5,7 @@ internal sealed class PageNavigationContext(IServiceScope serviceScope) : IDispo
     public IServiceScope ServiceScope => serviceScope;
     public bool Entered { get; set; }
     public bool Appeared { get; set; }
+    internal Action? OnDispose { get; set; }
 
     private static readonly BindableProperty _navigationContextProperty = BindableProperty.CreateAttached("PageNavigationContext", typeof(PageNavigationContext), typeof(PageNavigationContext), null);
 
@@ -30,5 +31,9 @@ public static void Dispose(Page page)
         page.ClearValue(_navigationContextProperty);
     }
 
-    public void Dispose() => serviceScope.Dispose();
+    public void Dispose()
+    {
+        OnDispose?.Invoke();
+        serviceScope.Dispose();
+    }
 }

Source/Nalu.Maui.Navigation/Nalu.Maui.Navigation.csproj

@@ -4,6 +4,7 @@
     <Description>.NET MAUI developer utilities</Description>
     <PackageTags>MAUI</PackageTags>
     <RootNamespace>Nalu</RootNamespace>
+    <NoWarn>NU5129</NoWarn>
   </PropertyGroup>
 
   <PropertyGroup Label="Build">

Source/Nalu.Maui.Navigation/NavigateCommand.cs

@@ -1,5 +1,6 @@
 namespace Nalu;
 
+using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Windows.Input;
 using Nalu.Internals;
@@ -61,9 +62,12 @@ public async void Execute(object? parameter)
             {
                 await navigationService.GoToAsync(navigation).ConfigureAwait(true);
             }
-            catch
+            catch (Exception ex)
             {
-                // Ignore
+                if (Debugger.IsAttached)
+                {
+                    Console.WriteLine(ex);
+                }
             }
 
             Interlocked.Exchange(ref _canExecute, 1);

Source/Nalu.Maui.Navigation/ShellInfo/ShellProxy.cs

@@ -106,9 +106,21 @@ public async Task PushAsync(string segmentName, Page page)
 
             var baseRoute = _navigationTarget ?? _shell.CurrentState.Location.OriginalString;
             var finalRoute = $"{baseRoute}/{segmentName}";
+
             Routing.UnRegisterRoute(finalRoute);
             Routing.RegisterRoute(finalRoute, new FixedRouteFactory(page));
 
+            // Apparently shell does not work well when the same segment is being used differently
+            // inside the same ShellContent:
+            // - //MyShellContent/MyPage
+            // - //MyShellContent/OtherPage/MyPage
+            // - //MyShellContent/MyPage/MyPage
+            // It always falls under the first one, even when we clearly specify an absolute Uri
+            // For now there's no apparent way to fix the recursive route, while on the other use cases
+            // We can just unregister the route when the page is disposed
+            var pageNavigationContext = PageNavigationContext.Get(page);
+            pageNavigationContext.OnDispose = () => Routing.UnRegisterRoute(finalRoute);
+
             if (_navigationTarget != null)
             {
                 _navigationTarget = finalRoute;