Target .NET6 instead of .NET Standard 2.0 and .NET Core 3.1 (#280)

* Set Target Framework to net6.0, remove conditional compilations and fix variety of arising nullability errors

* Fix typos

* Use static where possible for private methods

* Fix typo in internal class name

* Improve style consistency in xml doc comments

* Simplify control flow

* Use Contains over IndexOf >= 0

* Modernize code style and adjust indentation for consistency

* Use discard over __

* Remove redundant annotations

src/Kestrel.Certificates/KestrelHttpsOptionsExtensions.cs

@@ -8,7 +8,7 @@
 namespace Microsoft.AspNetCore.Hosting;
 
 /// <summary>
-/// API for configuring Kestrel certificiate options
+/// API for configuring Kestrel certificate options
 /// </summary>
 public static class KestrelHttpsOptionsExtensions
 {
@@ -22,7 +22,7 @@ public static HttpsConnectionAdapterOptions UseServerCertificateSelector(
         this HttpsConnectionAdapterOptions httpsOptions,
         IServerCertificateSelector certificateSelector)
     {
-        httpsOptions.ServerCertificateSelector = certificateSelector.Select;
+        httpsOptions.ServerCertificateSelector = certificateSelector.Select!;
         return httpsOptions;
     }
 }

src/Kestrel.Certificates/McMaster.AspNetCore.Kestrel.Certificates.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp3.1;netstandard2.0</TargetFrameworks>
+    <TargetFramework>net6.0</TargetFramework>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <Nullable>enable</Nullable>
     <IsPackable>true</IsPackable>
@@ -13,12 +13,9 @@ This library includes API for dynamically selecting which HTTPS certificate to u
     <PackageVersion Condition="'$(IncludePreReleaseLabelInPackageVersion)' == 'true'">$(PackageVersion)-$(VersionSuffix)</PackageVersion>
   </PropertyGroup>
 
-  <ItemGroup Condition="'$(TargetFramework)' == 'netcoreapp3.1'">
+  <ItemGroup>
     <FrameworkReference Include="Microsoft.AspNetCore.App" />
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
-    <PackageReference Include="Microsoft.AspNetCore.Server.Kestrel.Core" Version="2.1.25" />
-  </ItemGroup>
 
 </Project>

src/LettuceEncrypt.Azure/AzureKeyVaultLettuceEncryptOptions.cs

@@ -1,9 +1,7 @@
 // Copyright (c) Nate McMaster.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#if FEATURE_VALIDATE_DATA_ANNOTATIONS
 using System.ComponentModel.DataAnnotations;
-#endif
 using Azure.Core;
 using Azure.Identity;
 using LettuceEncrypt.Accounts;
@@ -18,10 +16,8 @@ public class AzureKeyVaultLettuceEncryptOptions
     /// <summary>
     /// Gets or sets the Url for the KeyVault instance.
     /// </summary>
-#if FEATURE_VALIDATE_DATA_ANNOTATIONS
     [Url]
     [Required]
-#endif
     public string AzureKeyVaultEndpoint { get; set; } = null!;
 
     /// <summary>
@@ -34,8 +30,6 @@ public class AzureKeyVaultLettuceEncryptOptions
     /// This is a JSON string which encodes the information in <see cref="AccountModel"/>.
     /// If not set, the name defaults to the name of the "le-account-${ACME server hostname}".
     /// </summary>
-#if FEATURE_VALIDATE_DATA_ANNOTATIONS
     [MaxLength(127)]
-#endif
     public string? AccountKeySecretName { get; set; }
 }

src/LettuceEncrypt.Azure/AzureLettuceEncryptExtensions.cs

@@ -57,13 +57,10 @@ public static ILettuceEncryptServiceBuilder PersistCertificatesToAzureKeyVault(
                 config?.Bind("LettuceEncrypt:AzureKeyVault", o));
         });
 
-        var options = services
+        services
             .AddOptions<AzureKeyVaultLettuceEncryptOptions>()
-            .Configure(configure);
-
-#if FEATURE_VALIDATE_DATA_ANNOTATIONS
-        options.ValidateDataAnnotations();
-#endif
+            .Configure(configure)
+            .ValidateDataAnnotations();
 
         return builder;
     }

src/LettuceEncrypt.Azure/LettuceEncrypt.Azure.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp3.1;netstandard2.0</TargetFrameworks>
+    <TargetFramework>net6.0</TargetFramework>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <Nullable>enable</Nullable>
     <IsPackable>true</IsPackable>
@@ -12,10 +12,6 @@ See https://nuget.org/packages/LettuceEncrypt for more details.
     </PackageDescription>
   </PropertyGroup>
 
-  <PropertyGroup Condition=" '$(TargetFramework)' == 'netcoreapp3.1' ">
-    <DefineConstants>$(DefineConstants);FEATURE_VALIDATE_DATA_ANNOTATIONS</DefineConstants>
-  </PropertyGroup>
-
   <ItemGroup>
     <PackageReference Include="Azure.Identity" Version="1.6.0" />
     <PackageReference Include="Azure.Security.KeyVault.Certificates" Version="4.3.0" />

src/LettuceEncrypt/FileSystemPersistenceExtensions.cs

@@ -22,7 +22,7 @@ public static class FileSystemStorageExtensions
     /// </summary>
     /// <param name="builder"></param>
     /// <param name="directory">The root directory for storing information. Information may be stored in subdirectories.</param>
-    /// <param name="pfxPassword">Set to null or empty for passwordless .pfx files.</param>
+    /// <param name="pfxPassword">Set to null or empty for password-less .pfx files.</param>
     /// <returns></returns>
     public static ILettuceEncryptServiceBuilder PersistDataToDirectory(
         this ILettuceEncryptServiceBuilder builder,
@@ -47,7 +47,7 @@ public static ILettuceEncryptServiceBuilder PersistDataToDirectory(
 
         foreach (var serviceDescriptor in otherFileSystemRepoServices)
         {
-            var otherRepo = (FileSystemCertificateRepository)serviceDescriptor.ImplementationInstance;
+            var otherRepo = (FileSystemCertificateRepository)serviceDescriptor.ImplementationInstance!;
             if (otherRepo.RootDir.Equals(directory))
             {
                 if (otherRepo.PfxPassword != pfxPassword)

src/LettuceEncrypt/ICertificateRepository.cs

@@ -13,7 +13,7 @@ public interface ICertificateRepository
     /// <summary>
     /// Save the certificate.
     /// </summary>
-    /// <param name="certificate">The certificate, including its private keys</param>
+    /// <param name="certificate">The certificate, including its private keys.</param>
     /// <param name="cancellationToken">A token which, when canceled, should stop any async operations.</param>
     /// <returns>A task which completes once the certificate is done saving.</returns>
     Task SaveAsync(X509Certificate2 certificate, CancellationToken cancellationToken);

src/LettuceEncrypt/ICertificateSource.cs

@@ -14,6 +14,6 @@ public interface ICertificateSource
     /// Gets available certificates from the source.
     /// </summary>
     /// <param name="cancellationToken">A cancellation token.</param>
-    /// <returns>A collection of certificates</returns>
+    /// <returns>A collection of certificates.</returns>
     Task<IEnumerable<X509Certificate2>> GetCertificatesAsync(CancellationToken cancellationToken);
 }

src/LettuceEncrypt/Internal/AcmeCertificateFactory.cs

@@ -12,10 +12,6 @@
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
 
-#if NETSTANDARD2_0
-using IHostApplicationLifetime = Microsoft.Extensions.Hosting.IApplicationLifetime;
-#endif
-
 namespace LettuceEncrypt.Internal;
 
 internal class AcmeCertificateFactory

src/LettuceEncrypt/Internal/AcmeCertificateLoader.cs

@@ -91,8 +91,6 @@ protected override async Task ExecuteAsync(CancellationToken stoppingToken)
     }
 
     private bool LettuceEncryptDomainNamesWereConfigured()
-    {
-        return _options.Value.DomainNames
+        => _options.Value.DomainNames
             .Any(w => !string.Equals("localhost", w, StringComparison.OrdinalIgnoreCase));
-    }
 }

src/LettuceEncrypt/Internal/AcmeClient.cs

@@ -38,12 +38,9 @@ public async Task<int> CreateAccountAsync(string emailAddress)
         var eabCredentials = _options.Value.EabCredentials;
         _accountContext = await _context.NewAccount(emailAddress, termsOfServiceAgreed: true, eabKeyId: eabCredentials.EabKeyId, eabKey: eabCredentials.EabKey, eabKeyAlg: eabCredentials.EabKeyAlg);
 
-        if (!int.TryParse(_accountContext.Location.Segments.Last(), out var accountId))
-        {
-            accountId = 0;
-        }
-
-        return accountId;
+        return int.TryParse(_accountContext.Location.Segments.Last(), out var accountId)
+            ? accountId
+            : 0;
     }
 
     public async Task<Uri> GetTermsOfServiceAsync()
@@ -122,5 +119,5 @@ public async Task<CertificateChain> GetCertificateAsync(CsrInfo csrInfo, IKey pr
         return await order.Generate(csrInfo, privateKey);
     }
 
-    private Exception MissingAccountContext() => new InvalidOperationException("Account wasn't initialized yet");
+    private static Exception MissingAccountContext() => new InvalidOperationException("Account wasn't initialized yet");
 }

src/LettuceEncrypt/Internal/AcmeStates/AcmeState.cs

@@ -12,7 +12,7 @@ internal interface IAcmeState
 
 internal class TerminalState : IAcmeState
 {
-    public static TerminalState Singleton { get; } = new TerminalState();
+    public static TerminalState Singleton { get; } = new();
 
     private TerminalState() { }
 

src/LettuceEncrypt/Internal/AcmeStates/BeginCertificateCreationState.cs

@@ -15,9 +15,11 @@ internal class BeginCertificateCreationState : AcmeState
     private readonly CertificateSelector _selector;
     private readonly IEnumerable<ICertificateRepository> _certificateRepositories;
 
-    public BeginCertificateCreationState(AcmeStateMachineContext context, ILogger<ServerStartupState> logger,
+    public BeginCertificateCreationState(
+        AcmeStateMachineContext context, ILogger<ServerStartupState> logger,
         IOptions<LettuceEncryptOptions> options, AcmeCertificateFactory acmeCertificateFactory,
-        CertificateSelector selector, IEnumerable<ICertificateRepository> certificateRepositories) : base(context)
+        CertificateSelector selector, IEnumerable<ICertificateRepository> certificateRepositories)
+        : base(context)
     {
         _logger = logger;
         _options = options;
@@ -60,9 +62,9 @@ private async Task SaveCertificateAsync(X509Certificate2 cert, CancellationToken
         _selector.Add(cert);
 
         var saveTasks = new List<Task>
-            {
-                Task.Delay(TimeSpan.FromMinutes(5), cancellationToken)
-            };
+        {
+            Task.Delay(TimeSpan.FromMinutes(5), cancellationToken)
+        };
 
         var errors = new List<Exception>();
         foreach (var repo in _certificateRepositories)

src/LettuceEncrypt/Internal/CertificateSelector.cs

@@ -37,7 +37,7 @@ public virtual void Add(X509Certificate2 certificate)
         {
             var selectedCert = AddWithDomainName(_certs, dnsName, certificate);
 
-            // Call preload once per certificate, but only if the cetificate is actually selected to be used
+            // Call preload once per certificate, but only if the certificate is actually selected to be used
             // for this domain. This is a small optimization which avoids preloading on a cert that may not be used.
             if (!preloaded && selectedCert == certificate)
             {
@@ -88,7 +88,6 @@ private X509Certificate2 AddWithDomainName(ConcurrentDictionary<string, X509Cert
 
     public X509Certificate2? Select(ConnectionContext context, string? domainName)
     {
-#if NETCOREAPP3_1_OR_GREATER
         if (_challengeCerts.Count > 0)
         {
             // var sslStream = context.Features.Get<SslStream>();
@@ -102,10 +101,6 @@ private X509Certificate2 AddWithDomainName(ConcurrentDictionary<string, X509Cert
                 return challengeCert;
             }
         }
-#elif NETSTANDARD2_0
-#else
-#error Update TFMs
-#endif
 
         if (domainName == null || !_certs.TryGetValue(domainName, out var retVal))
         {
@@ -117,7 +112,7 @@ private X509Certificate2 AddWithDomainName(ConcurrentDictionary<string, X509Cert
 
     public void Reset(string domainName)
     {
-        _certs.TryRemove(domainName, out var _);
+        _certs.TryRemove(domainName, out _);
     }
 
     public bool TryGet(string domainName, out X509Certificate2? certificate)
@@ -136,9 +131,9 @@ private void PreloadIntermediateCertificates(X509Certificate2 certificate)
         using var chain = new X509Chain
         {
             ChainPolicy =
-                {
-                    RevocationMode = X509RevocationMode.NoCheck
-                }
+            {
+                RevocationMode = X509RevocationMode.NoCheck
+            }
         };
 
         var commonName = X509CertificateHelpers.GetCommonName(certificate);

src/LettuceEncrypt/Internal/DefaultCertificateAuthorityConfiguration.cs

@@ -6,10 +6,6 @@
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Options;
 
-#if NETSTANDARD2_0
-using IHostEnvironment = Microsoft.Extensions.Hosting.IHostingEnvironment;
-#endif
-
 namespace LettuceEncrypt.Internal;
 
 internal class DefaultCertificateAuthorityConfiguration : ICertificateAuthorityConfiguration

src/LettuceEncrypt/Internal/DeveloperCertLoader.cs

@@ -5,10 +5,6 @@
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 
-#if NETSTANDARD2_0
-using IHostEnvironment = Microsoft.Extensions.Hosting.IHostingEnvironment;
-#endif
-
 namespace LettuceEncrypt.Internal;
 
 /// <summary>

src/LettuceEncrypt/Internal/DomainOwnershipValidator.cs

@@ -6,10 +6,6 @@
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 
-#if NETSTANDARD2_0
-using IHostApplicationLifetime = Microsoft.Extensions.Hosting.IApplicationLifetime;
-#endif
-
 namespace LettuceEncrypt.Internal;
 
 internal abstract class DomainOwnershipValidator

src/LettuceEncrypt/Internal/FileSystemAccountStore.cs

@@ -53,7 +53,7 @@ public FileSystemAccountStore(
         return default;
     }
 
-    private async Task<AccountModel?> Deserialize(FileInfo jsonFile, CancellationToken cancellationToken)
+    private static async Task<AccountModel?> Deserialize(FileInfo jsonFile, CancellationToken cancellationToken)
     {
         using var fileStream = jsonFile.OpenRead();
         var deserializeOptions = new JsonSerializerOptions

src/LettuceEncrypt/Internal/Http01DomainValidator.cs

@@ -6,19 +6,17 @@
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 
-#if NETSTANDARD2_0
-using IHostApplicationLifetime = Microsoft.Extensions.Hosting.IApplicationLifetime;
-#endif
-
 namespace LettuceEncrypt.Internal;
 
 internal class Http01DomainValidator : DomainOwnershipValidator
 {
     private readonly IHttpChallengeResponseStore _challengeStore;
 
-    public Http01DomainValidator(IHttpChallengeResponseStore challengeStore,
+    public Http01DomainValidator(
+        IHttpChallengeResponseStore challengeStore,
         IHostApplicationLifetime appLifetime,
-        AcmeClient client, ILogger logger, string domainName) : base(appLifetime, client, logger, domainName)
+        AcmeClient client, ILogger logger, string domainName)
+        : base(appLifetime, client, logger, domainName)
     {
         _challengeStore = challengeStore;
     }

src/LettuceEncrypt/Internal/HttpChallengeResponseMiddleware.cs

@@ -38,6 +38,6 @@ public async Task InvokeAsync(HttpContext context, RequestDelegate next)
 
         context.Response.ContentLength = value?.Length ?? 0;
         context.Response.ContentType = "application/octet-stream";
-        await context.Response.WriteAsync(value, context.RequestAborted);
+        await context.Response.WriteAsync(value!, context.RequestAborted);
     }
 }

src/LettuceEncrypt/Internal/IHttpChallengeResponseStore.cs

@@ -1,13 +1,11 @@
 // Copyright (c) Nate McMaster.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-using System.Diagnostics.CodeAnalysis;
-
 namespace LettuceEncrypt.Internal;
 
 internal interface IHttpChallengeResponseStore
 {
     void AddChallengeResponse(string token, string response);
 
-    bool TryGetResponse(string token, [MaybeNullWhen(false)] out string? value);
+    bool TryGetResponse(string token, out string? value);
 }

src/LettuceEncrypt/Internal/IO/PhysicalConsole.cs

@@ -1,11 +1,13 @@
 // Copyright (c) Nate McMaster.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System.Diagnostics.CodeAnalysis;
+
 namespace LettuceEncrypt.Internal.IO;
 
 internal class PhysicalConsole : IConsole
 {
-    public static PhysicalConsole Singleton { get; } = new PhysicalConsole();
+    public static PhysicalConsole Singleton { get; } = new();
 
     private PhysicalConsole()
     {
@@ -25,6 +27,8 @@ public ConsoleColor ForegroundColor
         set => Console.ForegroundColor = value;
     }
 
+    [SuppressMessage("Interoperability", "CA1416:Validate platform compatibility",
+        Justification = "Annotation introduced after .NET Core 3.1. Behavior is no different in .NET 6.")]
     public bool CursorVisible
     {
         get => Console.CursorVisible;
@@ -34,5 +38,5 @@ public bool CursorVisible
     public void WriteLine(string line) => Console.WriteLine(line);
     public void Write(string line) => Console.Write(line);
     public void ResetColor() => Console.ResetColor();
-    public string ReadLine() => Console.ReadLine();
+    public string ReadLine() => Console.ReadLine()!;
 }