Extract the default exception formatter in an internal method

Author: 0xced

src/Log4NetTextFormatter.cs

@@ -130,6 +130,13 @@ public void Format(LogEvent logEvent, TextWriter output)
         output.Write(_options.XmlWriterSettings.NewLineChars);
     }
 
+    /// <summary>
+    /// The default exception formatter. Calls the <see cref="Exception.ToString"/> method on the exception.
+    /// </summary>
+    /// <param name="exception">The exception to format.</param>
+    /// <returns>The formatted exception.</returns>
+    internal static string DefaultExceptionFormatter(Exception exception) => exception.ToString();
+
     /// <summary>
     /// Write the log event into the XML writer.
     /// </summary>
@@ -426,7 +433,7 @@ private void WriteException(LogEvent logEvent, XmlWriter writer)
         catch (Exception formattingException)
         {
             Debugging.SelfLog.WriteLine($"[{GetType().FullName}] An exception was thrown while formatting an exception. Using the default exception formatter.\n{formattingException}");
-            return exception.ToString();
+            return DefaultExceptionFormatter(exception);
         }
     }
 

src/Log4NetTextFormatterOptionsBuilder.cs

@@ -47,7 +47,7 @@ internal Log4NetTextFormatterOptionsBuilder()
     private PropertyFilter _filterProperty = (_, _) => true;
 
     /// <summary>See <see cref="UseExceptionFormatter"/></summary>
-    private ExceptionFormatter _formatException = exception => exception.ToString();
+    private ExceptionFormatter _formatException = Log4NetTextFormatter.DefaultExceptionFormatter;
 
     /// <summary>
     /// Sets the <see cref="IFormatProvider"/> used when formatting message and properties of log4net events.
@@ -206,5 +206,6 @@ private static XmlWriterSettings CreateXmlWriterSettings(LineEnding lineEnding,
 /// <summary>
 /// Represents the method that formats an <see cref="Exception"/>.
 /// </summary>
-/// <param name="exception">The exception to be formatted.</param>
+/// <param name="exception">The exception to format.</param>
+/// <returns>The formatted exception.</returns>
 public delegate string ExceptionFormatter(Exception exception);