MicrosoftConsoleLayoutRenderer - For Hosting Lifetime Startup Messages (

#490)

src/NLog.Extensions.Logging/LayoutRenderers/MicrosoftConsoleLayoutRenderer.cs

@@ -0,0 +1,76 @@
+using System.Linq;
+using System.Text;
+using NLog.Config;
+using NLog.LayoutRenderers;
+
+namespace NLog.Extensions.Logging
+{
+    /// <summary>
+    /// Renders output that simulates simple Microsoft Console Logger. Useful for Hosting Lifetime Startup Messages.
+    /// </summary>
+    [LayoutRenderer("MicrosoftConsoleLayout")]
+    [ThreadSafe]
+    [ThreadAgnostic]
+    class MicrosoftConsoleLayoutRenderer : LayoutRenderer
+    {
+        private static readonly string[] EventIdMapper = Enumerable.Range(0, 50).Select(id => id.ToString()).ToArray();
+
+        /// <inheritdoc />
+        protected override void Append(StringBuilder builder, LogEventInfo logEvent)
+        {
+            var microsoftLogLevel = ConvertLogLevel(logEvent.Level);
+            builder.Append(microsoftLogLevel);
+            builder.Append(": ");
+            builder.Append(logEvent.LoggerName);
+            builder.Append("[");
+            int eventId = 0;
+            if (logEvent.HasProperties && logEvent.Properties.TryGetValue("EventId_Id", out var eventIdValue))
+            {
+                if (eventIdValue is int)
+                    eventId = (int)eventIdValue;
+                else if (!int.TryParse(eventIdValue?.ToString() ?? string.Empty, out eventId))
+                    eventId = 0;
+            }
+            else
+            {
+                eventId = 0;
+            }
+            builder.Append(ConvertEventId(eventId));
+            builder.Append("]");
+            builder.Append(System.Environment.NewLine);
+            builder.Append("      ");
+            builder.Append(logEvent.FormattedMessage);
+            if (logEvent.Exception != null)
+            {
+                builder.Append(System.Environment.NewLine);
+                builder.Append(logEvent.Exception.ToString());
+            }
+        }
+
+        static string ConvertEventId(int eventId)
+        {
+            if (eventId == 0)
+                return "0";
+            else if (eventId > 0 || eventId < EventIdMapper.Length)
+                return EventIdMapper[eventId];
+            else
+                return eventId.ToString();
+        }
+
+        string ConvertLogLevel(LogLevel logLevel)
+        {
+            if (logLevel == LogLevel.Trace)
+                return "trce";
+            else if (logLevel == LogLevel.Debug)
+                return "dbug";
+            else if (logLevel == LogLevel.Info)
+                return "info";
+            else if (logLevel == LogLevel.Warn)
+                return "warn";
+            else if (logLevel == LogLevel.Error)
+                return "fail";
+            else
+                return "crit";  // Fatal
+        }
+    }
+}

test/NLog.Extensions.Logging.Tests/MicrosoftConsoleLayoutRendererTest.cs

@@ -0,0 +1,28 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using Xunit;
+
+namespace NLog.Extensions.Logging.Tests
+{
+    public class MicrosoftConsoleLayoutRendererTest
+    {
+        [Fact]
+        public void MicrosoftConsoleLayoutRenderer_NullEvent()
+        {
+            var layoutRenderer = new MicrosoftConsoleLayoutRenderer();
+            var result = layoutRenderer.Render(LogEventInfo.CreateNullEvent());
+            Assert.Contains("crit: [0]", result);
+        }
+
+        [Fact]
+        public void MicrosoftConsoleLayoutRenderer_ExceptionEvent()
+        {
+            var layoutRenderer = new MicrosoftConsoleLayoutRenderer();
+            var exception = new ArgumentException("Test");
+            var eventId = 42;
+            var result = layoutRenderer.Render(new LogEventInfo(LogLevel.Error, "MyLogger", null, "Alert {EventId_Id}", new object[] { eventId }, exception));
+            Assert.Equal($"fail: MyLogger[{eventId}]{Environment.NewLine}      Alert 42{Environment.NewLine}{exception}", result);
+        }
+    }
+}