fix: copy MemberNotNull attribute internally for use with NETSTANDARD2.1 code

Author: egil

src/bunit.core/System.Diagnostics.CodeAnalysis/MemberNotNullAttribute.cs

@@ -0,0 +1,29 @@
+#if NETSTANDARD2_1
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Diagnostics.CodeAnalysis;
+
+/// <summary>
+/// Specifies that the method or property will ensure that the listed field and property members have not-null values.
+/// </summary>
+[AttributeUsage(AttributeTargets.Method | AttributeTargets.Property, Inherited = false, AllowMultiple = true)]
+internal sealed class MemberNotNullAttribute : Attribute
+{
+	/// <summary>Initializes the attribute with a field or property member.</summary>
+	/// <param name="member">
+	/// The field or property member that is promised to be not-null.
+	/// </param>
+	[SuppressMessage("Design", "CA1019:Define accessors for attribute arguments", Justification = "Copied from dotnet team.")]
+	public MemberNotNullAttribute(string member) => Members = new[] { member };
+
+	/// <summary>Initializes the attribute with the list of field and property members.</summary>
+	/// <param name="members">
+	/// The list of field and property members that are promised to be not-null.
+	/// </param>
+	public MemberNotNullAttribute(params string[] members) => Members = members;
+
+	/// <summary>Gets field or property member names.</summary>
+	public string[] Members { get; }
+}
+#endif

src/bunit.core/TestServiceProvider.cs

@@ -97,24 +97,21 @@ public void UseServiceProviderFactory<TContainerBuilder>(IServiceProviderFactory
 			throw new ArgumentNullException(nameof(serviceProviderFactory));
 		}
 
-		UseServiceProviderFactory(
-			serviceCollection =>
-			{
-				var containerBuilder = serviceProviderFactory.CreateBuilder(serviceCollection);
-				configure?.Invoke(containerBuilder);
-				return serviceProviderFactory.CreateServiceProvider(containerBuilder);
-			});
+		UseServiceProviderFactory(serviceCollection =>
+		{
+			var containerBuilder = serviceProviderFactory.CreateBuilder(serviceCollection);
+			configure?.Invoke(containerBuilder);
+			return serviceProviderFactory.CreateServiceProvider(containerBuilder);
+		});
 	}
 
 	/// <summary>
 	/// Creates the underlying service provider. Throws if it was already build.
-	/// Automatically called while getting a service if unitialized.
+	/// Automatically called while getting a service if uninitialized.
 	/// No longer will accept calls to the <c>AddService</c>'s methods.
 	/// See <see cref="IsProviderInitialized"/>
 	/// </summary>
-#if !NETSTANDARD2_1
 	[MemberNotNull(nameof(serviceProvider))]
-#endif
 	private void InitializeProvider()
 	{
 		CheckInitializedAndThrow();
@@ -155,7 +152,7 @@ public object GetService(Type serviceType)
 		if (serviceProvider is null)
 			InitializeProvider();
 
-		var result = serviceProvider!.GetService(serviceType);
+		var result = serviceProvider.GetService(serviceType);
 
 		if (result is null && fallbackServiceProvider is not null)
 			result = fallbackServiceProvider.GetService(serviceType);