CommunityToolkit.WinUI.UI.Controls crashes WinUI 3 NavigationViewItem.Icon

[LeftTwixWand]

Describe the bug

My ProjectPeunion solution is crashes, when I'm trying to use NavigationViewItem.Icon property with the CommunityToolkit.WinUI.UI.Controls library. The error is:
Microsoft.UI.Xaml.Markup.XamlParseException: 'XAML parsing failed.'

• Is this bug a regression in the toolkit? If so, what toolkit version did you last see it work:

Steps to Reproduce

• Can this be reproduced in the Sample App? (Either in a sample as-is or with new XAML pasted in the editor.) If so, please provide custom XAML or steps to reproduce. If not, let us know why it can't be reproduced (e.g. more complex setup, environment, dependencies, etc...)

All you need to do:

• Create a new solution with the ProjectReunion version 0.5.5
• nuget: install-package Microsoft.ProjectReunion -Version 0.5.5
• Add NavigationView with one item, that contains the Icon property:

<NavigationView>
   <NavigationView.MenuItems>
      <NavigationViewItem Content="Text" Icon="AddFriend"/>
   </NavigationView.MenuItems>
</NavigationView>

Or clone my sample solution:

• git clone https://github.com/LeftTwixWand/ReunionAppBug.git

Screenshots

Environment

NuGet Package(s): 
 CommunityToolkit.WinUI.UI.Controls Version="7.0.1"
 Microsoft.ProjectReunion Version="0.5.5" 

Windows 10 Build Number:
- [ ] Fall Creators Update (16299)
- [ ] April 2018 Update (17134)
- [ ] October 2018 Update (17763)
- [ ] May 2019 Update (18362)
- [x] May 2020 Update (19041)
- [ ] Insider Build (build number: )

App min and target version:
- [ ] Fall Creators Update (16299)
- [ ] April 2018 Update (17134)
- [ ] October 2018 Update (17763)
- [x] May 2019 Update (18362)
- [ ] May 2020 Update (19041)
- [ ] Insider Build (xxxxx)

Device form factor:
- [x] Desktop
- [ ] Xbox
- [ ] Surface Hub
- [ ] IoT

Visual Studio 
- [ ] 2017 (version: )
- [ ] 2019 (version: ) 
- [x] 2019 Preview (version: 16.10.0 Preview 2.0)

Hello LeftTwixWand, thank you for opening an issue with us!

I have automatically added a "needs triage" label to help get things started. Our team will analyze and investigate the issue, and escalate it to the relevant team if possible. Other community members may also look into the issue and provide feedback 🙌

[Kyaa-dost]

@LeftTwixWand Thanks for checking but this issue is specifically a WinUI issue. Please try reporting in the WinUI repo.

[michael-hawker]

@azchohfi thoughts on what might be going on here?

[LeftTwixWand]

@Kyaa-dost, but if I'm removing the toolkit library - it works fine...

[azchohfi]

No idea why this is happening. I was able to reproduce this issue.
@RealTommyKlein, any idea what is going on?

[LeftTwixWand]

It's so strange. I've created an absolutely identical WinUI 3 project, added Community controls library, and everything is working. I don't know, what's wrong with this one: https://github.com/LeftTwixWand/ReunionAppBug.git

[michael-hawker]

@LeftTwixWand can you do a full diff against the two folders to see if there's anything that may be different?

[michael-hawker]

Someone else has reported something that looks the same in this discussion: #3912 (comment) (apparently GitHub doesn't show mentions in the issue history for discussions).

[RealTommyKlein]

@LeftTwixWand @azchohfi - thanks for the report. It looks like a change in the Reunion 0.5.5 servicing release isn't playing nicely with Reunion 0.5.0 (some metadata in the Microsoft.WinUI.dll projection was stripped out). This issue can happen when an app and a library it consumes are targeting different Reunion versions, due to the differences in metadata. This should be fixed in the next Reunion servicing release, but in the meantime the app and library should target the same version. For the repro app, it's targeting 0.5.5 while the community toolkit is on 0.5.0. I was able to workaround this by changing the app's Reunion version from 0.5.5 to 0.5.0

[azchohfi]

Ok, thank you Tommy, this is very helpful! In the meantime, we can also push a new version of the toolkit based on 0.5.5.
@michael-hawker , are you ok with us doing this asap?

[michael-hawker]

@azchohfi yeah sounds good. Originally we thought we'd be able to play nicely with the update, but seems like I've heard about a couple of potential issues at this point. Just a rev a 7.0.x version of the WinUI packages and we should be good! Thanks Alex!