How do I prevent installing nuget packages that aren't 100% .Net Core 2.0 compatible?

Question

I understand that .Net Core 2 has a compatibility shim that allows it use Nuget packages that don't specifically target .Net Core/Standard 2. This gives it access to 70% of Nuget. Great - nice feature.

How do I prevent installing nuget packages that aren't fully compatible with .Net Core 2/.Net Standard 2? Or warn me at point of installing that it is being used with the shim?

I created a new .Net Core 2.0 project installed EF 6.1.3 (which I knew didn't work) and nothing prevented me or warned that it didn't target .Net Standard <=2 at the point of install.

I am happy to "run with scissors" but I kind of feel I should be getting a warning before I install MVC5 and EF 6.1.3 into a .Net Core 2 application. I would really like to prevent junior devs from installing unsupported packages etc.

I guess further to Matt Ward answer - my main point is - can it be detected that something is actually 100% compatible at install or are we always just in the situation where we need to make determination ourselves that package works "well enough". I hoped that there was a technical mechanism that detected missing coverage API coverage and could tell us that the nuget package may not operate as it did before. So I guess MS say 70% compatibility - I want to fail if I try to install the 30%

Answer 1

Installing Entity Framework 6.1.3 into a .NET Core 2.0 project there is a NU1701 warning in the Errors window about Entity Framework 6.1.3 being restored using .NET Framework 4.6.1 and that it may not be fully compatible.

You could turn the NU1701 warning into an error in the project so you could not install any NuGet package that does not explicitly support .NET Core 2.0. This can be done by adding the WarningAsErrors property to the project.

<PropertyGroup>
  <OutputType>Exe</OutputType>
  <TargetFramework>netcoreapp2.0</TargetFramework>
  <WarningsAsErrors>NU1701</WarningsAsErrors>
</PropertyGroup>

Then if you try to install Entity Framework 6.1.3 the restore will fail, the changes will be rolled back, and the NuGet package will not be installed.

You can also set the DisableImplicitAssetTargetFallback property to true which will prevent .NET 4.6.1 being added to the AssetTargetFallback property which is used when checking NuGet package compatibility with .NET Core 2.0 projects.

<PropertyGroup>
  <OutputType>Exe</OutputType>
  <TargetFramework>netcoreapp2.0</TargetFramework>
  <DisableImplicitAssetTargetFallback>true</DisableImplicitAssetTargetFallback>
</PropertyGroup>