[dotnet] Sending GeckoDriver output to a log file.

Related to #12273

Author: diemol

dotnet/src/webdriver/DriverService.cs

@@ -284,7 +284,7 @@ protected virtual void Dispose(bool disposing)
     /// Raises the <see cref="DriverProcessStarting"/> event.
     /// </summary>
     /// <param name="eventArgs">A <see cref="DriverProcessStartingEventArgs"/> that contains the event data.</param>
-    protected void OnDriverProcessStarting(DriverProcessStartingEventArgs eventArgs)
+    protected virtual void OnDriverProcessStarting(DriverProcessStartingEventArgs eventArgs)
     {
         if (eventArgs == null)
         {
@@ -298,7 +298,7 @@ protected void OnDriverProcessStarting(DriverProcessStartingEventArgs eventArgs)
     /// Raises the <see cref="DriverProcessStarted"/> event.
     /// </summary>
     /// <param name="eventArgs">A <see cref="DriverProcessStartedEventArgs"/> that contains the event data.</param>
-    protected void OnDriverProcessStarted(DriverProcessStartedEventArgs eventArgs)
+    protected virtual void OnDriverProcessStarted(DriverProcessStartedEventArgs eventArgs)
     {
         if (eventArgs == null)
         {

dotnet/src/webdriver/Firefox/FirefoxDriverService.cs

@@ -22,6 +22,7 @@
 using System.Globalization;
 using System.IO;
 using System.Text;
+using System.Threading.Tasks;
 
 namespace OpenQA.Selenium.Firefox;
 
@@ -31,6 +32,11 @@ namespace OpenQA.Selenium.Firefox;
 public sealed class FirefoxDriverService : DriverService
 {
     private const string DefaultFirefoxDriverServiceFileName = "geckodriver";
+    
+    /// <summary>
+    /// Process management fields for the log writer.
+    /// </summary>
+    private StreamWriter? logWriter;
 
     /// <summary>
     /// Initializes a new instance of the <see cref="FirefoxDriverService"/> class.
@@ -87,6 +93,16 @@ protected override DriverOptions GetDefaultDriverOptions()
     /// </summary>
     public bool OpenBrowserToolbox { get; set; }
 
+    /// <summary>
+    /// Gets or sets the file path where log output should be written.
+    /// </summary>
+    /// <remarks>
+    /// A <see langword="null"/> or <see cref="string.Empty"/> value indicates no log file to specify.
+    /// This approach takes the process output and redirects it to a file because GeckoDriver does not
+    /// offer a way to specify a log file path directly.
+    /// </remarks>
+    public string? LogPath { get; set; }
+    
     /// <summary>
     /// Gets or sets the level at which log output is displayed.
     /// </summary>
@@ -176,6 +192,74 @@ protected override string CommandLineArguments
             return argsBuilder.ToString().Trim();
         }
     }
+    
+    /// <summary>
+    /// Handles the event when the driver service process is starting.
+    /// </summary>
+    /// <param name="eventArgs">The event arguments containing information about the driver service process.</param>
+    /// <remarks>
+    /// This method initializes a log writer if a log path is specified and redirects output streams to capture logs.
+    /// </remarks>
+    protected override void OnDriverProcessStarting(DriverProcessStartingEventArgs eventArgs)
+    {
+        if (!string.IsNullOrEmpty(this.LogPath))
+        {
+            string? directory = Path.GetDirectoryName(this.LogPath);
+            if (!string.IsNullOrEmpty(directory) && !Directory.Exists(directory))
+            {
+                Directory.CreateDirectory(directory);
+            }
+    
+            // Initialize the log writer
+            logWriter = new StreamWriter(this.LogPath, append: true) { AutoFlush = true };
+    
+            // Configure process to redirect output
+            eventArgs.DriverServiceProcessStartInfo.RedirectStandardOutput = true;
+            eventArgs.DriverServiceProcessStartInfo.RedirectStandardError = true;
+        }
+    
+        base.OnDriverProcessStarting(eventArgs);
+    }
+    
+    /// <summary>
+    /// Handles the event when the driver process has started.
+    /// </summary>
+    /// <param name="eventArgs">The event arguments containing information about the started driver process.</param>
+    /// <remarks>
+    /// This method reads the output and error streams asynchronously and writes them to the log file if available.
+    /// </remarks>
+    protected override void OnDriverProcessStarted(DriverProcessStartedEventArgs eventArgs)
+    {
+        if (logWriter == null) return;
+        if (eventArgs.StandardOutputStreamReader != null)
+        {
+            _ = Task.Run(() => ReadStreamAsync(eventArgs.StandardOutputStreamReader));
+        }
+    
+        if (eventArgs.StandardErrorStreamReader != null)
+        {
+            _ = Task.Run(() => ReadStreamAsync(eventArgs.StandardErrorStreamReader));                
+        }
+
+        base.OnDriverProcessStarted(eventArgs);
+    }
+
+    /// <summary>
+    /// Disposes of the resources used by the <see cref="FirefoxDriverService"/> instance.
+    /// </summary>
+    /// <param name="disposing">A value indicating whether the method is being called from Dispose.</param>
+    /// <remarks>
+    /// If disposing is true, it disposes of the log writer if it exists.
+    /// </remarks>
+    protected override void Dispose(bool disposing)
+    {
+        if (logWriter != null && disposing)
+        {
+            logWriter.Dispose();
+        }
+
+        base.Dispose(disposing);
+    }
 
     /// <summary>
     /// Creates a default instance of the FirefoxDriverService.
@@ -258,4 +342,16 @@ private static string FirefoxDriverServiceFileName()
 
         return fileName;
     }
+    
+    private async Task ReadStreamAsync(StreamReader reader)
+    {
+        string? line;
+        while ((line = await reader.ReadLineAsync()) != null)
+        {
+            if (logWriter != null)
+            {
+                logWriter.WriteLine($"{DateTime.Now:yyyy-MM-dd HH:mm:ss.fff} {line}");
+            }
+        }
+    }
 }