From 14821ae2a16d9173b3abc93f7c3c877106a09158 Mon Sep 17 00:00:00 2001
From: iuri dotta <dotta.iuri@gmail.com>
Date: Wed, 6 Dec 2023 22:10:10 -0300
Subject: [PATCH] Fix MAUI RoutedViewHost Navigation (#3692)

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[Contribute](https://github.com/reactiveui/reactiveui#contribute)
section of the README -->

**What kind of change does this PR introduce?**
<!-- Bug fix, feature, docs update, ... -->
Bug fix

**What is the current behavior?**
<!-- You can also link to an open issue here. -->
#3640 When 'RoutedViewHost' is activated, it calls
'SyncNavigationStacksAsync', which pushes a page for the current
ViewModel. However, the Router.Navigate subscription is also triggered,
creating and pushing a new page for the same ViewModel.

**What is the new behavior?**
<!-- If this is a feature change -->
To fix this, I filtered Navigate to execute the action only when the
NavigationStacks have different sizes, since it seems that is what the
Navigate subscription was supposed to do anyway. I think this makes the
subsequent call to SyncNavigationStacksAsync() useless. Should I remove
it?

**What might this PR break?**
RoutedViewHost Navigate subscription.


**Please check if the PR fulfills these requirements**
- [ ] Tests for the changes have been added (for bug fixes / features)
- [ ] Docs have been added / updated (for bug fixes / features)

**Other information**:
I was informed that there were no tests for MAUI and no documentation
seemed to be present either.
---
 src/ReactiveUI.Maui/RoutedViewHost.cs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/ReactiveUI.Maui/RoutedViewHost.cs b/src/ReactiveUI.Maui/RoutedViewHost.cs
index bffebeb44c..1ee1ce70a9 100644
--- a/src/ReactiveUI.Maui/RoutedViewHost.cs
+++ b/src/ReactiveUI.Maui/RoutedViewHost.cs
@@ -76,6 +76,7 @@ public RoutedViewHost()
 
             Router?
                 .Navigate
+                .Where(_ => Navigation.NavigationStack.Count != Router.NavigationStack.Count)
                 .ObserveOn(RxApp.MainThreadScheduler)
                 .SelectMany(_ => PagesForViewModel(Router.GetCurrentViewModel()))
                 .SelectMany(async page =>