Consider removing the extensibility that allows other package managers to be shown as compatible

[nkolev92]

Create any PR/PJ based project and open the PM UI and see that there's a

Incompatible: Use Bower instead

when we list those packages.

This is achieved with an extensibility point that allows other "alternative" managers to talk to NuGet and advertise if they're the preferred option for those packages.
Code here.

The reason why these packages are incompatible is because they contain content, the mutable v2 kind.
However, if you read the ASP.NET docs, there's conflicting information.

These 2 packages are perfect examples of what contentFiles should be used for.

We should consider removing this "AlternativePackageManagerProviders" goo, and work with the jquery/bootstrap nuget package maintainers to make these 2 packages PR compatible.

[nkolev92]

Another customer filled a similar issue to this one:
https://developercommunity.visualstudio.com/content/problem/225023/aspnet-core-web.html
//cc @rrelyea
This a part of the ASP.NET projects should support PackageReference effort.

[StingyJack]

We should consider removing this "AlternativePackageManagerProviders" goo, and work with the jquery/bootstrap nuget package maintainers to make these 2 packages PR compatible.

Or you should consider that in some cases we need to be able to modify the content that would be distributed by the package into our project to address issues with it or for any other reason. Its frustrating to be held hostage to a bug that you can correct, but are artificially forbidden from doing so. Tools should enable, not restrict.

[nkolev92]

//cc @rrelyea
The existence of this is not allowing us to fixed certain delays in the PM UI construction ~50ms to 100ms depending on the load.
Basically the below method is foced to be synchrnous https://github.com/NuGet/NuGet.Client/blob/5c2db09662f99d96a47182b761fcea6df1625a5a/src/NuGet.Clients/NuGet.Tools/NuGetUIFactory.cs#L75 since some methods in the implementers rely on being called on the UI thread https://github.com/NuGet/NuGet.Client/blob/5c2db09662f99d96a47182b761fcea6df1625a5a/src/NuGet.Clients/NuGet.PackageManagement.UI/Utility/PackageManagerProviderUtility.cs#L11.

Basically I can't make this method async.
This is obviously an implementation bug on Bower side.

We should retriage it again.

[donnie-msft]

Related (now closed) bug I filed dotnet/aspnetcore#27480