[dotnet] Fully annotate nullability on HttpCommandExecutor

Author: RenderMichael

dotnet/src/webdriver/Remote/HttpCommandExecutor.cs

@@ -30,6 +30,8 @@
 using System.Threading;
 using System.Threading.Tasks;
 
+#nullable enable
+
 namespace OpenQA.Selenium.Remote
 {
     /// <summary>
@@ -47,7 +49,8 @@ public class HttpCommandExecutor : ICommandExecutor
         private readonly TimeSpan serverResponseTimeout;
         private bool isDisposed;
         private CommandInfoRepository commandInfoRepository = new W3CWireProtocolCommandInfoRepository();
-        private HttpClient client;
+        private HttpClient? client;
+        private readonly object _createClientLock = new();
 
         private static readonly ILogger _logger = Log.GetLogger<HttpCommandExecutor>();
 
@@ -56,6 +59,7 @@ public class HttpCommandExecutor : ICommandExecutor
         /// </summary>
         /// <param name="addressOfRemoteServer">Address of the WebDriver Server</param>
         /// <param name="timeout">The timeout within which the server must respond.</param>
+        /// <exception cref="ArgumentNullException">If <paramref name="addressOfRemoteServer"/> is <see langword="null"/>.</exception>
         public HttpCommandExecutor(Uri addressOfRemoteServer, TimeSpan timeout)
             : this(addressOfRemoteServer, timeout, true)
         {
@@ -91,14 +95,14 @@ public HttpCommandExecutor(Uri addressOfRemoteServer, TimeSpan timeout, bool ena
         /// Occurs when the <see cref="HttpCommandExecutor"/> is sending an HTTP
         /// request to the remote end WebDriver implementation.
         /// </summary>
-        public event EventHandler<SendingRemoteHttpRequestEventArgs> SendingRemoteHttpRequest;
+        public event EventHandler<SendingRemoteHttpRequestEventArgs>? SendingRemoteHttpRequest;
 
         /// <summary>
         /// Gets or sets an <see cref="IWebProxy"/> object to be used to proxy requests
         /// between this <see cref="HttpCommandExecutor"/> and the remote end WebDriver
         /// implementation.
         /// </summary>
-        public IWebProxy Proxy { get; set; }
+        public IWebProxy? Proxy { get; set; }
 
         /// <summary>
         /// Gets or sets a value indicating whether keep-alive is enabled for HTTP
@@ -167,17 +171,12 @@ public virtual async Task<Response> ExecuteAsync(Command commandToExecute)
                 _logger.Debug($"Executing command: {commandToExecute}");
             }
 
-            HttpCommandInfo info = this.commandInfoRepository.GetCommandInfo<HttpCommandInfo>(commandToExecute.Name);
+            HttpCommandInfo? info = this.commandInfoRepository.GetCommandInfo<HttpCommandInfo>(commandToExecute.Name);
             if (info == null)
             {
                 throw new NotImplementedException(string.Format("The command you are attempting to execute, {0}, does not exist in the protocol dialect used by the remote end.", commandToExecute.Name));
             }
 
-            if (this.client == null)
-            {
-                this.CreateHttpClient();
-            }
-
             HttpRequestInfo requestInfo = new HttpRequestInfo(this.remoteServerUri, commandToExecute, info);
             HttpResponseInfo responseInfo;
             try
@@ -216,42 +215,55 @@ protected virtual void OnSendingRemoteHttpRequest(SendingRemoteHttpRequestEventA
                 throw new ArgumentNullException(nameof(eventArgs), "eventArgs must not be null");
             }
 
-            if (this.SendingRemoteHttpRequest != null)
-            {
-                this.SendingRemoteHttpRequest(this, eventArgs);
-            }
+            this.SendingRemoteHttpRequest?.Invoke(this, eventArgs);
         }
 
-        private void CreateHttpClient()
+        private HttpClient Client
         {
-            HttpClientHandler httpClientHandler = new HttpClientHandler();
-            string userInfo = this.remoteServerUri.UserInfo;
-            if (!string.IsNullOrEmpty(userInfo) && userInfo.Contains(":"))
-            {
-                string[] userInfoComponents = this.remoteServerUri.UserInfo.Split(new char[] { ':' }, 2);
-                httpClientHandler.Credentials = new NetworkCredential(userInfoComponents[0], userInfoComponents[1]);
-                httpClientHandler.PreAuthenticate = true;
-            }
-
-            httpClientHandler.Proxy = this.Proxy;
-
-            HttpMessageHandler handler = httpClientHandler;
-
-            if (_logger.IsEnabled(LogEventLevel.Trace))
+            get
             {
-                handler = new DiagnosticsHttpHandler(httpClientHandler, _logger);
-            }
+                if (this.client is null)
+                {
+                    lock (_createClientLock)
+                    {
+                        if (this.client is null)
+                        {
+                            HttpClientHandler httpClientHandler = new HttpClientHandler();
+                            string userInfo = this.remoteServerUri.UserInfo;
+                            if (!string.IsNullOrEmpty(userInfo) && userInfo.Contains(":"))
+                            {
+                                string[] userInfoComponents = this.remoteServerUri.UserInfo.Split(new char[] { ':' }, 2);
+                                httpClientHandler.Credentials = new NetworkCredential(userInfoComponents[0], userInfoComponents[1]);
+                                httpClientHandler.PreAuthenticate = true;
+                            }
+
+                            httpClientHandler.Proxy = this.Proxy;
+
+                            HttpMessageHandler handler = httpClientHandler;
+
+                            if (_logger.IsEnabled(LogEventLevel.Trace))
+                            {
+                                handler = new DiagnosticsHttpHandler(httpClientHandler, _logger);
+                            }
+
+                            var client = new HttpClient(handler);
+                            client.DefaultRequestHeaders.UserAgent.ParseAdd(this.UserAgent);
+                            client.DefaultRequestHeaders.Accept.ParseAdd(RequestAcceptHeader);
+                            client.DefaultRequestHeaders.ExpectContinue = false;
+                            if (!this.IsKeepAliveEnabled)
+                            {
+                                client.DefaultRequestHeaders.Connection.ParseAdd("close");
+                            }
+
+                            client.Timeout = this.serverResponseTimeout;
+
+                            this.client = client;
+                        }
+                    }
+                }
 
-            this.client = new HttpClient(handler);
-            this.client.DefaultRequestHeaders.UserAgent.ParseAdd(this.UserAgent);
-            this.client.DefaultRequestHeaders.Accept.ParseAdd(RequestAcceptHeader);
-            this.client.DefaultRequestHeaders.ExpectContinue = false;
-            if (!this.IsKeepAliveEnabled)
-            {
-                this.client.DefaultRequestHeaders.Connection.ParseAdd("close");
+                return this.client;
             }
-
-            this.client.Timeout = this.serverResponseTimeout;
         }
 
         private async Task<HttpResponseInfo> MakeHttpRequest(HttpRequestInfo requestInfo)
@@ -288,7 +300,7 @@ private async Task<HttpResponseInfo> MakeHttpRequest(HttpRequestInfo requestInfo
                     requestMessage.Content.Headers.ContentType = contentTypeHeader;
                 }
 
-                using (HttpResponseMessage responseMessage = await this.client.SendAsync(requestMessage).ConfigureAwait(false))
+                using (HttpResponseMessage responseMessage = await this.Client.SendAsync(requestMessage).ConfigureAwait(false))
                 {
                     var responseBody = await responseMessage.Content.ReadAsStringAsync().ConfigureAwait(false);
                     var responseContentType = responseMessage.Content.Headers.ContentType?.ToString();
@@ -331,8 +343,6 @@ private Response CreateResponse(HttpResponseInfo responseInfo)
             return response;
         }
 
-#nullable enable
-
         /// <summary>
         /// Releases all resources used by the <see cref="HttpCommandExecutor"/>.
         /// </summary>