PackageManager.InstallPackageAsync() throws NullReferenceException

[ericanastas]

NuGet product used: Nuget Libraries
NuGet version (5.7.0:
VS version: VS 2017
OS version: Win 10 (1909)

Details about Problem

I'm working on a plug-in management system built on top of Nuget similar to Chocolatey, PowerShell Gallery etc. I wanted to use the newer V3 libraries but the amount of abstraction and the lack of documentation is becoming a serious challenge for me.

The responses to issue #6161 have been helpful, as well as the blog posts mentioned there. However, I'm still failing to get simple prototype working that will download and extract a package.

Here's my test code
https://github.com/ericanastas/nuget-packagemanagment-test

       private static void Main(string[] args)
        {
            try
            {
                var curDir = System.IO.Directory.GetCurrentDirectory();
                ISettings settings = Settings.LoadSpecificSettings(curDir, Settings.DefaultSettingsFileName);

                List<Lazy<INuGetResourceProvider>> resourceProviders = new List<Lazy<INuGetResourceProvider>>();
                resourceProviders.AddRange(NuGet.Protocol.Core.Types.Repository.Provider.GetCoreV3());  // Add v3 API support
                IPackageSourceProvider packageSourceProvider = new PackageSourceProvider(settings);
                SourceRepositoryProvider sourceRepositoryProvider = new SourceRepositoryProvider(packageSourceProvider, resourceProviders);

                string projectRoot = System.IO.Path.GetFullPath("ProjectRoot");
                if (!System.IO.Directory.Exists(projectRoot)) System.IO.Directory.CreateDirectory(projectRoot);

                FolderNuGetProject nuGetProject = new FolderNuGetProject(projectRoot);

                string packagesFolderPath = System.IO.Path.GetFullPath("Packages");
                if (!System.IO.Directory.Exists(packagesFolderPath)) System.IO.Directory.CreateDirectory(packagesFolderPath);

                NuGetPackageManager packageManager = new NuGetPackageManager(sourceRepositoryProvider, settings, packagesFolderPath)
                {
                    PackagesFolderNuGetProject = nuGetProject
                };

                bool allowPrereleaseVersions = true;
                bool allowUnlisted = true;
                DependencyBehavior dependencyBehavior = DependencyBehavior.Lowest;

                ResolutionContext resolutionContext = new ResolutionContext(
                         dependencyBehavior, allowPrereleaseVersions, allowUnlisted, VersionConstraints.None);

                INuGetProjectContext projectContext = new ConsoleProjectContext(NullLogger.Instance);

                IEnumerable<SourceRepository> primarySourceRepositories = sourceRepositoryProvider.GetRepositories();

                //packageIdentity
                string packageId = "Newtonsoft.Json";
                string packageVersion = "12.0.3";
                PackageIdentity packageIdentity = new PackageIdentity(packageId, new NuGet.Versioning.NuGetVersion(packageVersion));

                var installPackageAsyncTask = packageManager.InstallPackageAsync(packageManager.PackagesFolderNuGetProject,
                    packageIdentity, resolutionContext, projectContext,
                    primarySourceRepositories, Array.Empty<SourceRepository>(), CancellationToken.None);

                installPackageAsyncTask.GetAwaiter().GetResult();
            }
            catch (Exception exp)
            {
                using (var sw = new System.IO.StreamWriter("error.txt"))
                {
                    sw.Write(exp.ToString());
                }

                Console.WriteLine(exp.ToString());
                throw;
            }
        }

And here's the NullReferenceException that is thrown at the end when I try to call InstallPackageAsync()

System.NullReferenceException: Object reference not set to an instance of an object.
   at NuGet.ProjectManagement.FolderNuGetProject.<>c__DisplayClass13_0.<<InstallPackageAsync>b__0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at NuGet.Common.ConcurrencyUtilities.<ExecuteWithFileLockedAsync>d__3`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at NuGet.Common.ConcurrencyUtilities.<ExecuteWithFileLockedAsync>d__3`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at NuGet.PackageManagement.NuGetPackageManager.<ExecuteInstallAsync>d__85.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task)
   at NuGet.PackageManagement.NuGetPackageManager.<ExecuteNuGetProjectActionsAsync>d__76.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at NuGet.PackageManagement.NuGetPackageManager.<ExecuteNuGetProjectActionsAsync>d__76.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at NuGet.PackageManagement.NuGetPackageManager.<ExecuteNuGetProjectActionsAsync>d__76.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at NuGet.PackageManagement.NuGetPackageManager.<InstallPackageAsync>d__48.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at NuGet.PackageManagement.NuGetPackageManager.<InstallPackageAsync>d__47.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
   at NugetTest.Program.Main(String[] args) in C:\Git\5ec64809061464dc19a1d4e39961c565\NugetTest\Program.cs:line 66

What am I missing here?

[donnie-msft]

FYI, there's been some recent work to add more examples of using the SDK. Here's a pointer to one of those:
https://docs.microsoft.com/en-us/nuget/reference/nuget-client-sdk#download-a-package