nuspec exclude="Analyzers" ineffective, analyzers are still brought in

[AArnott]

Details about Problem

NuGet product used (NuGet.exe | VS UI | Package Manager Console | dotnet.exe): dotnet.exe

dotnet.exe --version (if appropriate): 2.2.200-preview-009431

Every single dependency in the streamjsonrpc 2.0.102-beta package has exclude="Build,Analyzers" on it. Yet installing it in a .NET Core project adds analyzers from the Microsoft.VisualStudio.Threading.Analyzers package, which streamjsonrpc indirectly depends on through its Microsoft.VisualStudio.Threading package dependency.

Detailed repro steps so we can see the same problem

1. Create a csproj with this content:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp2.2</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="StreamJsonRpc" Version="2.0.102-beta" />
  </ItemGroup>  

</Project>

2. Then create a Program.cs file with this content:

using System;
using System.Threading.Tasks;

namespace ConsoleApp30
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello World!");
            FooAsync().Wait();
        }

        static async Task FooAsync() {

        }
    }
}

3. run dotnet build

EXPECTED

No VSTHRD002 build warning.

ACTUAL

The build warnings include one from VSTHRD002.

See sample: ConsoleApp30.zip

[nkolev92]

Thanks for filing this @AArnott

As analyzers were initially done without any work from NuGet team, this is a well known gap.

I consider this a duplicate of #6279.
I am closing this now in favor of that, please let me know if you disagree.