I've lost all debug (stdout, breakpoints) since migrating my RNW UWP app to a WAP project. Is there a way to get debug back?

[shirakaba]

This may be out-of-scope for RNW as it's more of a general Windows application development question, but this is the only community I'm connected to and it's a real-world issue in RNW app development, so I thought I'd ask here just in case anyone could help!

I'm making an old architecture RNW app (UWP, C++, RNW v0.73) and trying to call a Win32 process. I'm following the recommendations made back in 2021 about how to use Win32 features from a React Native for Windows application (though for other readers, XAML islands is recommended nowadays due to changes coming with the New Architecture). This 2021 approach effectively applied Matteo Pagani's 2019 guide about the Desktop Bridge to a React Native Windows app. The outline is:

1. Create a Windows Application Packaging Project (WAP project) that wraps both the UWP app and the Win32 app.
2. Specify the Win32 app as an App Service extension of the UWP app with full-trust capabilities.
3. Enable the UWP app to launch the Win32 app via FullTrustProcessLauncher.LaunchFullTrustProcessForAppAsync and communicate with it via an App Service Connection.

I believe I've followed these steps successfully, comparing to Matteo's demo project. However, I've lost all debug. I have no visibility of stdout or stderr for the UWP or Win32 app (just the WAP app), and my breakpoints aren't hit in either process.

And yet, when I try creating a new app from the New Arch template, I find that it creates a WAP project containing a Win32 app and the debug breakpoints and stdout work just fine in there, so I believe there must be a way to get this working. Is there anything I may have overlooked? Thank you for any pointers!

[shirakaba]

Finally found it by studying the New Architecture C++ app template (after learning that it, too, is a WAP project):

By following the 2021 guide, I'd been missing these two crucial lines:

react-native-windows/vnext/templates/cpp-app/windows/MyApp.Package/MyApp.Package.wapproj

Lines 8 to 9 in b716fe4

	<DebuggerType>NativeOnly</DebuggerType>
	<BackgroundTaskDebugEngines>NativeOnly</BackgroundTaskDebugEngines>

It looks like the guide's sample project had been missing those lines, too:

https://github.com/microsoft/react-native-windows-samples/blob/5cc852a7838ff5183e7272201c7e3f6e0f384507/samples/AppServiceDemo/windows/appservicedemo.Package/appservicedemo.Package.wapproj#L52-L59

I simply had to add those two lines to my .wapproj and I got my debug back!