Project parser does not handle the new 'Update' attribute available for .NET Core projects.

If an ItemGroup includes entries which use the new 'Update' attribute in Visual Studio\MSBuild, the Project Parser will not recognize those files (those files will not be returned to the caller).

```


PreserveNewest


```

please see the documentation @ https://docs.microsoft.com/en-us/visualstudio/msbuild/item-element-msbuild

Start by locating the Project Parser entry point that processes ItemGroup entries and reproduce the example with an Update attribute. Check how matching files are returned to the caller; done means files selected through Update, such as the migration paths shown, are recognized and returned.

Written by the indexing model from the issue text.