set scope and build validation in dev when no options provided (#99199)

Author: wcsanders1

src/libraries/Microsoft.Extensions.Hosting/src/HostBuilder.cs

@@ -37,13 +37,15 @@ public partial class HostBuilder : IHostBuilder
         private HostingEnvironment? _hostingEnvironment;
         private IServiceProvider? _appServices;
         private PhysicalFileProvider? _defaultProvider;
+        private readonly bool _defaultProviderFactoryUsed;
 
         /// <summary>
         /// Initializes a new instance of <see cref="HostBuilder"/>.
         /// </summary>
         public HostBuilder()
         {
             _serviceProviderFactory = new ServiceFactoryAdapter<IServiceCollection>(new DefaultServiceProviderFactory());
+            _defaultProviderFactoryUsed = true;
         }
 
         /// <summary>
@@ -344,6 +346,11 @@ private void InitializeServiceProvider()
                 configureServicesAction(_hostBuilderContext!, services);
             }
 
+            if (_hostBuilderContext!.HostingEnvironment.IsDevelopment() && _defaultProviderFactoryUsed)
+            {
+                _serviceProviderFactory = new ServiceFactoryAdapter<IServiceCollection>(new DefaultServiceProviderFactory(new ServiceProviderOptions { ValidateOnBuild = true, ValidateScopes = true }));
+            }
+
             object containerBuilder = _serviceProviderFactory.CreateBuilder(services);
 
             foreach (IConfigureContainerAdapter containerAction in _configureContainerActions)

src/libraries/Microsoft.Extensions.Hosting/tests/UnitTests/HostBuilderTests.cs

@@ -533,6 +533,33 @@ public void CustomContainerTypeMismatchThrows()
             Assert.Throws<InvalidCastException>(() => hostBuilder.Build());
         }
 
+        [Fact]
+        public void ScopeValidationEnabledInDevelopment()
+        {
+            using var host = new HostBuilder()
+                .UseEnvironment(Environments.Development)
+                .ConfigureServices(serices =>
+                {
+                    serices.AddScoped<ServiceA>();
+                })
+                .Build();
+
+            Assert.Throws<InvalidOperationException>(() => { host.Services.GetRequiredService<ServiceA>(); });
+        }
+
+        [Fact]
+        public void ValidateOnBuildEnabledInDevelopment()
+        {
+            var hostBuilder = new HostBuilder()
+                .UseEnvironment(Environments.Development)
+                .ConfigureServices(serices =>
+                {
+                    serices.AddSingleton<ServiceC>();
+                });
+
+            Assert.Throws<AggregateException>(() => hostBuilder.Build());
+        }
+
         [Fact]
         public void HostingContextContainsAppConfigurationDuringConfigureLogging()
         {