fix: GetCurrentPage for PrismWindow.Page throwing exception

src/Maui/Prism.Maui/Common/MvvmHelpers.cs

@@ -88,12 +88,14 @@ private static void DestroyChildren(IView page)
                 {
                     DestroyPage(item);
                 }
+
                 break;
             case NavigationPage navigationPage:
                 foreach (var item in navigationPage.Navigation.NavigationStack.Reverse())
                 {
                     DestroyPage(item);
                 }
+
                 break;
         }
     }
@@ -104,11 +106,12 @@ public static void DestroyWithModalStack(Page? page, IList<Page?> modalStack)
         {
             DestroyPage(childPage);
         }
+
         DestroyPage(page);
     }
 
     public static T? GetImplementerFromViewOrViewModel<T>(object view)
-            where T : class
+        where T : class
     {
         if (view is T viewAsT)
         {
@@ -281,8 +284,9 @@ public static void SetCurrentPageDelegate(Func<Page, Page?> getCurrentPageDelega
         {
             FlyoutPage flyout => GetTarget(flyout.Detail),
             TabbedPage tabbed => GetTarget(tabbed.CurrentPage),
-            NavigationPage navigation => GetTarget(navigation.CurrentPage),
+            NavigationPage navigation => GetTarget(navigation.CurrentPage) ?? navigation,
             ContentPage page => page,
+            null => null,
             _ => throw new NotSupportedException($"The page type '{target.GetType().FullName}' is not supported.")
         };
     }
@@ -298,12 +302,12 @@ public static void SetCurrentPageDelegate(Func<Page, Page?> getCurrentPageDelega
         {
             if (target is IDialogContainer)
             {
-                if (page.Parent is Page parentPage)
+                return page.Parent switch
                 {
-                    return GetTarget(parentPage);
-                }
-
-                throw new InvalidOperationException("Unable to determine the current page.");
+                    Page parentPage => GetTarget(parentPage),
+                    Window window => GetTarget(window.Page),
+                    _ => throw new InvalidOperationException("Unable to determine the current page.")
+                };
             }
 
             return page.Parent switch

tests/Maui/Prism.Maui.Tests/Fixtures/Common/MvvmHelperFixture.cs

@@ -0,0 +1,135 @@
+using Prism.Common;
+
+namespace Prism.Maui.Tests.Fixtures.Common;
+
+public class MvvmHelperFixture
+{
+    /// <summary>
+    /// This test was introduced to verify GH3143
+    /// </summary>
+    /// <a href="https://github.com/PrismLibrary/Prism/issues/3143">Git Hub Issue 3143</a>
+    [Fact]
+    public async Task GetCurrentPageFromFlyoutPageWithModalReturnsDetailPage()
+    {
+        // Given
+        var flyout = new FlyoutPage
+            { Flyout = new ContentPage { Title = "Title" }, Detail = new NavigationPage(), };
+        var window = new PrismWindow { Page = flyout };
+        await window.Navigation.PushModalAsync(new DialogContainerPage());
+
+        // When
+        var result = MvvmHelpers.GetCurrentPage(window.Page);
+
+        // Then
+        Assert.Equal(flyout.Detail, result);
+    }
+
+    /// <summary>
+    /// This test was introduced to verify GH3143
+    /// </summary>
+    /// <a href="https://github.com/PrismLibrary/Prism/issues/3143">Git Hub Issue 3143</a>
+    [Fact]
+    public async Task GetCurrentPageFromComplexFlyoutPageWithModalReturnsCorrectPage()
+    {
+        // Given
+        var expected = new ContentPage { Title = "D" };
+        var navigationPage = new NavigationPage();
+        await navigationPage.PushAsync(new ContentPage { Title = "A" });
+        await navigationPage.PushAsync(new ContentPage { Title = "B" });
+        await navigationPage.PushAsync(new ContentPage { Title = "C" });
+        await navigationPage.PushAsync(expected);
+
+        var window = new Window
+        {
+            Page = new FlyoutPage
+                { Flyout = new ContentPage { Title = "Title" }, Detail = navigationPage, }
+        };
+
+        await window.Navigation.PushModalAsync(new DialogContainerPage());
+
+        // When
+        var result = MvvmHelpers.GetCurrentPage(window.Page);
+
+        // Then
+        Assert.Equal(expected, result);
+    }
+
+    /// <summary>
+    /// This test was introduced to verify GH3143
+    /// </summary>
+    /// <a href="https://github.com/PrismLibrary/Prism/issues/3143">Git Hub Issue 3143</a>
+    [Fact]
+    public async Task GetCurrentPageFromNavigationPageWithModalReturnsContentPage()
+    {
+        // Given
+        var expected = new ContentPage();
+        var window = new Window { Page = new NavigationPage(expected) };
+        await window.Navigation.PushModalAsync(new DialogContainerPage());
+
+        // When
+        var result = MvvmHelpers.GetCurrentPage(window.Page);
+
+        // Then
+        Assert.Equal(expected, result);
+    }
+
+    /// <summary>
+    /// This test was introduced to verify GH3143
+    /// </summary>
+    /// <a href="https://github.com/PrismLibrary/Prism/issues/3143">Git Hub Issue 3143</a>
+    [Fact]
+    public async Task GetCurrentPageFromContentPageWithModalReturnsContentPage()
+    {
+        // Given
+        var expected = new ContentPage { Title = "Title" };
+        var window = new Window { Page = expected };
+        await window.Navigation.PushModalAsync(new DialogContainerPage());
+
+        // When
+        var result = MvvmHelpers.GetCurrentPage(window.Page);
+
+        // Then
+        Assert.Equal(expected, result);
+    }
+
+    /// <summary>
+    /// This test was introduced to verify GH3143
+    /// </summary>
+    /// <a href="https://github.com/PrismLibrary/Prism/issues/3143">Git Hub Issue 3143</a>
+    [Fact(Skip = "System.InvalidOperationException\nBindableObject was not instantiated on a thread with a dispatcher nor does the current application have a dispatcher.")]
+    public async Task GetCurrentPageFromTabbedPageWithModalReturnsContentPage()
+    {
+        // Given
+        var expected = new ContentPage();
+        var tabbedPage = new TabbedPage { Title = "Tab", Children = { expected }};
+        var window = new Window { Page = tabbedPage };
+        await window.Navigation.PushModalAsync(new DialogContainerPage());
+
+        // When
+        var result = MvvmHelpers.GetCurrentPage(window.Page);
+
+        // Then
+        Assert.Equal(expected, result);
+    }
+
+    /// <summary>
+    /// This test was introduced to verify GH3143
+    /// </summary>
+    /// <a href="https://github.com/PrismLibrary/Prism/issues/3143">Git Hub Issue 3143</a>
+    [Fact(Skip = "System.InvalidOperationException\nBindableObject was not instantiated on a thread with a dispatcher nor does the current application have a dispatcher.")]
+    public async Task GetCurrentPageFromTabbedNavigationPageWithModalReturnsContentPage()
+    {
+        // Given
+        var expected = new ContentPage();
+        var navigationPage = new NavigationPage(expected);
+        var tabbedPage = new TabbedPage { Title = "Tab", Children = { navigationPage }};
+        var window = new Window { Page = tabbedPage };
+        await window.Navigation.PushModalAsync(new DialogContainerPage());
+
+        // When
+        var result = MvvmHelpers.GetCurrentPage(window.Page);
+
+        // Then
+        Assert.Equal(expected, result);
+    }
+}