Supporting netcoreapp3.0 with McMaster.Extensions.Hosting.CommandLine

I am trying to use this library with netcoreapp3.0. I get a failure whenever I try to launch the app.

'Method 'UseServiceProviderFactory' in type 'Microsoft.Extensions.Hosting.HostBuilder' from assembly 'Microsoft.Extensions.Hosting, Version=2.1.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60' does not have an implementation.'

I think this is because McMaster.Extensions.Hosting.CommandLine.csproj refers to Microsoft.Extensions.Hosting@2.1.0.

My main method looks like

  private static async Task<int> Main(string[] args)
        {
            return await new HostBuilder()
                 .ConfigureAppConfiguration((hostContext, configApp) =>
                 {
                     var tokenProvider = new AzureServiceTokenProvider();
                     var kv = new KeyVaultClient(new KeyVaultClient.AuthenticationCallback(tokenProvider.KeyVaultTokenCallback));

                     configApp.SetBasePath(Directory.GetCurrentDirectory());
                     configApp.AddJsonFile("appsettings.json", optional: true);
                     configApp.AddJsonFile(
                         $"appsettings.{hostContext.HostingEnvironment.EnvironmentName}.json",
                         optional: true);
                     configApp.AddCommandLine(args);

                     configApp.AddAzureKeyVault(
                       $"https://{configApp.Build().GetValue<string>("Vault")}.vault.azure.net/",
                       kv,
                       new DefaultKeyVaultSecretManager());
                 })

               .ConfigureServices((context, services) =>
               {
                   var provider = services.BuildServiceProvider();                 

                   services.RegisterDbContext();
               })

           .RunCommandLineApplicationAsync<Program>(args);
        }

[natemcmaster]

I’m currently favoring solution (3) - see draft commit in https://github.com/natemcmaster/CommandLineUtils/commit/494bbc848b0c020ffa13062838b98e13052ba243. The advantage is that it maximizes compatibility. CommandLineUtils would not need to multi-target to support both 2.1 and 3.0. (It also fits with my philosophy on dependencies is that class libraries — that is, class libraries should minimize dependencies and use the lowest version possible to maximize compatibility.) The disadvantage is that it’s a packaging breaking change; anyone using CommandLineUtils doesn’t explicitly depend on Microsoft.Extensions.Hosting would need to add a new package reference.

Thoughts?

[natemcmaster]

I’m hesitant on option 1 because it seems odd to me that the version of the dependency should vary based on target framework. Microsoft.Extensions.Hosting and CommandLineUtils are both netstandard2.0 libraries. If we go with option 1, netcoreapp3.0 users are forced into a higher version of Hosting, even if they were trying to use Hosting 2.1 on netcorapp3.0 (a perfectly valid use case, btw.)

I think I’d like to wait on this one (so, do option 2), and revisit this for the next major version of CommandLineUtils.