NuGet PackageManager.InstallPackageAsync引发NullReferenceException

如何解决NuGet PackageManager.InstallPackageAsync引发NullReferenceException

我正在开发一个基于Nuget构建的插件管理系统，类似于Chocolatey，PowerShell Gallery等。

我想使用较新的V3 libraries，而不要使用Chocolatey使用的已弃用的V2 Nuget.Core库。但是，V3库中的大量抽象和缺乏文档对我来说已成为一个严峻的挑战。我仍然无法获得可以下载并提取软件包的简单原型。

这是我的测试代码： 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;
            }
        }

这是我尝试致电NullReferenceException时最后抛出的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

我在这里想念什么？

解决方法

我目前也在纠结这个。我发现 this repository 的来源很有用。

要使示例代码正常工作，请将 projectContext 初始化更改为：

var clientPolicyContext = ClientPolicyContext.GetClientPolicy(settings,NullLogger.Instance);
INuGetProjectContext projectContext = new ConsoleProjectContext(NullLogger.Instance)
{
    PackageExtractionContext = new PackageExtractionContext(
        PackageSaveMode.Defaultv3,PackageExtractionBehavior.XmlDocFileSaveMode,clientPolicyContext,NullLogger.Instance
    )
};

在生产代码中，您可能希望使用真正的记录器而不是 NullLogger。