[Group 3] Enable nullable annotations for `Microsoft.Extensions.Hosti…

…ng.Abstractions` (#65403)

* First pass (src)

* Update Microsoft.Extensions.Hosting.Abstractions.cs

* Update HostBuilderContext

* Values of Properties cannot be null

src/libraries/Microsoft.Extensions.Hosting.Abstractions/ref/Microsoft.Extensions.Hosting.Abstractions.cs

@@ -17,7 +17,7 @@ namespace Microsoft.Extensions.Hosting
     public abstract partial class BackgroundService : Microsoft.Extensions.Hosting.IHostedService, System.IDisposable
     {
         protected BackgroundService() { }
-        public virtual System.Threading.Tasks.Task ExecuteTask { get { throw null; } }
+        public virtual System.Threading.Tasks.Task? ExecuteTask { get { throw null; } }
         public virtual void Dispose() { }
         protected abstract System.Threading.Tasks.Task ExecuteAsync(System.Threading.CancellationToken stoppingToken);
         public virtual System.Threading.Tasks.Task StartAsync(System.Threading.CancellationToken cancellationToken) { throw null; }
@@ -106,8 +106,8 @@ public partial interface IHostBuilder
         Microsoft.Extensions.Hosting.IHostBuilder ConfigureContainer<TContainerBuilder>(System.Action<Microsoft.Extensions.Hosting.HostBuilderContext, TContainerBuilder> configureDelegate);
         Microsoft.Extensions.Hosting.IHostBuilder ConfigureHostConfiguration(System.Action<Microsoft.Extensions.Configuration.IConfigurationBuilder> configureDelegate);
         Microsoft.Extensions.Hosting.IHostBuilder ConfigureServices(System.Action<Microsoft.Extensions.Hosting.HostBuilderContext, Microsoft.Extensions.DependencyInjection.IServiceCollection> configureDelegate);
-        Microsoft.Extensions.Hosting.IHostBuilder UseServiceProviderFactory<TContainerBuilder>(Microsoft.Extensions.DependencyInjection.IServiceProviderFactory<TContainerBuilder> factory);
-        Microsoft.Extensions.Hosting.IHostBuilder UseServiceProviderFactory<TContainerBuilder>(System.Func<Microsoft.Extensions.Hosting.HostBuilderContext, Microsoft.Extensions.DependencyInjection.IServiceProviderFactory<TContainerBuilder>> factory);
+        Microsoft.Extensions.Hosting.IHostBuilder UseServiceProviderFactory<TContainerBuilder>(Microsoft.Extensions.DependencyInjection.IServiceProviderFactory<TContainerBuilder> factory) where TContainerBuilder : notnull;
+        Microsoft.Extensions.Hosting.IHostBuilder UseServiceProviderFactory<TContainerBuilder>(System.Func<Microsoft.Extensions.Hosting.HostBuilderContext, Microsoft.Extensions.DependencyInjection.IServiceProviderFactory<TContainerBuilder>> factory) where TContainerBuilder : notnull;
     }
     public partial interface IHostedService
     {
@@ -116,15 +116,15 @@ public partial interface IHostedService
     }
     public partial interface IHostEnvironment
     {
-        string ApplicationName { get; set; }
+        string? ApplicationName { get; set; }
         Microsoft.Extensions.FileProviders.IFileProvider ContentRootFileProvider { get; set; }
         string ContentRootPath { get; set; }
         string EnvironmentName { get; set; }
     }
     [System.ObsoleteAttribute("IHostingEnvironment has been deprecated. Use Microsoft.Extensions.Hosting.IHostEnvironment instead.")]
     public partial interface IHostingEnvironment
     {
-        string ApplicationName { get; set; }
+        string? ApplicationName { get; set; }
         Microsoft.Extensions.FileProviders.IFileProvider ContentRootFileProvider { get; set; }
         string ContentRootPath { get; set; }
         string EnvironmentName { get; set; }

src/libraries/Microsoft.Extensions.Hosting.Abstractions/ref/Microsoft.Extensions.Hosting.Abstractions.csproj

@@ -1,6 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppMinimum);netstandard2.1;netstandard2.0;$(NetFrameworkMinimum)</TargetFrameworks>
+    <Nullable>enable</Nullable>
     <NoWarn>$(NoWarn);CS0618</NoWarn>
   </PropertyGroup>
 

src/libraries/Microsoft.Extensions.Hosting.Abstractions/src/BackgroundService.cs

@@ -12,16 +12,16 @@ namespace Microsoft.Extensions.Hosting
     /// </summary>
     public abstract class BackgroundService : IHostedService, IDisposable
     {
-        private Task _executeTask;
-        private CancellationTokenSource _stoppingCts;
+        private Task? _executeTask;
+        private CancellationTokenSource? _stoppingCts;
 
         /// <summary>
         /// Gets the Task that executes the background operation.
         /// </summary>
         /// <remarks>
         /// Will return <see langword="null"/> if the background operation hasn't started.
         /// </remarks>
-        public virtual Task ExecuteTask => _executeTask;
+        public virtual Task? ExecuteTask => _executeTask;
 
         /// <summary>
         /// This method is called when the <see cref="IHostedService"/> starts. The implementation should return a task that represents
@@ -69,7 +69,7 @@ public virtual async Task StopAsync(CancellationToken cancellationToken)
             try
             {
                 // Signal cancellation to the executing method
-                _stoppingCts.Cancel();
+                _stoppingCts!.Cancel();
             }
             finally
             {

src/libraries/Microsoft.Extensions.Hosting.Abstractions/src/HostBuilderContext.cs

@@ -19,12 +19,12 @@ public HostBuilderContext(IDictionary<object, object> properties!!)
         /// <summary>
         /// The <see cref="IHostEnvironment" /> initialized by the <see cref="IHost" />.
         /// </summary>
-        public IHostEnvironment HostingEnvironment { get; set; }
+        public IHostEnvironment HostingEnvironment { get; set; } = null!;
 
         /// <summary>
         /// The <see cref="IConfiguration" /> containing the merged configuration of the application and the <see cref="IHost" />.
         /// </summary>
-        public IConfiguration Configuration { get; set; }
+        public IConfiguration Configuration { get; set; } = null!;
 
         /// <summary>
         /// A central location for sharing state between components during the host building process.

src/libraries/Microsoft.Extensions.Hosting.Abstractions/src/HostingAbstractionsHostExtensions.cs

@@ -86,18 +86,18 @@ public static async Task RunAsync(this IHost host, CancellationToken token = def
         /// <returns>The <see cref="Task"/> that represents the asynchronous operation.</returns>
         public static async Task WaitForShutdownAsync(this IHost host, CancellationToken token = default)
         {
-            IHostApplicationLifetime applicationLifetime = host.Services.GetService<IHostApplicationLifetime>();
+            IHostApplicationLifetime applicationLifetime = host.Services.GetRequiredService<IHostApplicationLifetime>();
 
             token.Register(state =>
             {
-                ((IHostApplicationLifetime)state).StopApplication();
+                ((IHostApplicationLifetime)state!).StopApplication();
             },
             applicationLifetime);
 
-            var waitForStop = new TaskCompletionSource<object>(TaskCreationOptions.RunContinuationsAsynchronously);
+            var waitForStop = new TaskCompletionSource<object?>(TaskCreationOptions.RunContinuationsAsynchronously);
             applicationLifetime.ApplicationStopping.Register(obj =>
             {
-                var tcs = (TaskCompletionSource<object>)obj;
+                var tcs = (TaskCompletionSource<object?>)obj!;
                 tcs.TrySetResult(null);
             }, waitForStop);
 

src/libraries/Microsoft.Extensions.Hosting.Abstractions/src/IHostBuilder.cs

@@ -51,14 +51,14 @@ public interface IHostBuilder
         /// <typeparam name="TContainerBuilder">The type of builder.</typeparam>
         /// <param name="factory">The factory to register.</param>
         /// <returns>The same instance of the <see cref="IHostBuilder"/> for chaining.</returns>
-        IHostBuilder UseServiceProviderFactory<TContainerBuilder>(IServiceProviderFactory<TContainerBuilder> factory);
+        IHostBuilder UseServiceProviderFactory<TContainerBuilder>(IServiceProviderFactory<TContainerBuilder> factory) where TContainerBuilder : notnull;
 
         /// <summary>
         /// Overrides the factory used to create the service provider.
         /// </summary>
         /// <typeparam name="TContainerBuilder">The type of builder.</typeparam>
         /// <returns>The same instance of the <see cref="IHostBuilder"/> for chaining.</returns>
-        IHostBuilder UseServiceProviderFactory<TContainerBuilder>(Func<HostBuilderContext, IServiceProviderFactory<TContainerBuilder>> factory);
+        IHostBuilder UseServiceProviderFactory<TContainerBuilder>(Func<HostBuilderContext, IServiceProviderFactory<TContainerBuilder>> factory) where TContainerBuilder : notnull;
 
         /// <summary>
         /// Enables configuring the instantiated dependency container. This can be called multiple times and

src/libraries/Microsoft.Extensions.Hosting.Abstractions/src/IHostEnvironment.cs

@@ -21,7 +21,7 @@ public interface IHostEnvironment
         /// Gets or sets the name of the application. This property is automatically set by the host to the assembly containing
         /// the application entry point.
         /// </summary>
-        string ApplicationName { get; set; }
+        string? ApplicationName { get; set; }
 
         /// <summary>
         /// Gets or sets the absolute path to the directory that contains the application content files.

src/libraries/Microsoft.Extensions.Hosting.Abstractions/src/IHostingEnvironment.cs

@@ -26,7 +26,7 @@ public interface IHostingEnvironment
         /// Gets or sets the name of the application. This property is automatically set by the host to the assembly containing
         /// the application entry point.
         /// </summary>
-        string ApplicationName { get; set; }
+        string? ApplicationName { get; set; }
 
         /// <summary>
         /// Gets or sets the absolute path to the directory that contains the application content files.

src/libraries/Microsoft.Extensions.Hosting.Abstractions/src/Microsoft.Extensions.Hosting.Abstractions.csproj

@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppMinimum);netstandard2.1;netstandard2.0;$(NetFrameworkMinimum)</TargetFrameworks>
+    <Nullable>enable</Nullable>
     <RootNamespace>Microsoft.Extensions.Hosting</RootNamespace>
     <EnableDefaultItems>true</EnableDefaultItems>
     <!-- Use targeting pack references instead of granular ones in the project file. -->