WhenEmpty - Optimize when IsFixedText (#6074)

snakefoot · web-flow · commit be28e5bf9185 · 2026-01-08T20:04:14.000+01:00
diff --git a/src/NLog/LayoutRenderers/Wrappers/WhenEmptyLayoutRendererWrapper.cs b/src/NLog/LayoutRenderers/Wrappers/WhenEmptyLayoutRendererWrapper.cs
@@ -70,7 +70,11 @@ protected override void InitializeLayoutRenderer()
 
             if (Inner is SimpleLayout innerLayout && WhenEmpty is SimpleLayout whenEmptyLayout)
             {
-                if ((innerLayout.IsFixedText || innerLayout.IsSimpleStringText) && (whenEmptyLayout.IsFixedText || whenEmptyLayout.IsSimpleStringText))
+                if (innerLayout.IsFixedText)
+                {
+                    _stringValueRenderer = ResolveFixedWhenEmpty(innerLayout, whenEmptyLayout);
+                }
+                else if (innerLayout.IsSimpleStringText && (whenEmptyLayout.IsFixedText || whenEmptyLayout.IsSimpleStringText))
                 {
                     _stringValueRenderer = (logEvent) =>
                     {
@@ -81,6 +85,24 @@ protected override void InitializeLayoutRenderer()
             }
         }
 
+        private static Func<LogEventInfo, string>? ResolveFixedWhenEmpty(SimpleLayout innerLayout, SimpleLayout whenEmptyLayout)
+        {
+            if (!string.IsNullOrEmpty(innerLayout.FixedText))
+            {
+                return (logEvent) => innerLayout.FixedText ?? string.Empty;
+            }
+            else if (whenEmptyLayout.IsFixedText)
+            {
+                return (logEvent) => whenEmptyLayout.FixedText ?? string.Empty;
+            }
+            else if (whenEmptyLayout.IsSimpleStringText)
+            {
+                return (logEvent) => whenEmptyLayout.Render(logEvent);
+            }
+
+            return null;
+        }
+
         /// <inheritdoc/>
         protected override void RenderInnerAndTransform(LogEventInfo logEvent, StringBuilder builder, int orgLength)
         {
