Add test to check support for custom destructuring extension Methods

Author: tsimbalar

test/Serilog.Settings.Configuration.Tests/ConfigurationSettingsTests.cs

@@ -679,5 +679,29 @@ private string GetDestructuredProperty(object x, string json)
             var result = evt.Properties["X"].ToString();
             return result;
         }
+
+        [Fact]
+        public void DestructuringWithCustomExtensionMethodIsApplied()
+        {
+            var json = @"{
+                ""Serilog"": {
+                    ""Using"": [""TestDummies""],
+                    ""Destructure"": [
+                    {
+                        ""Name"": ""WithDummyHardCodedString"",
+                        ""Args"": { ""hardCodedString"": ""hardcoded"" }
+                    }]
+                }
+            }";
+
+            LogEvent evt = null;
+            var log = ConfigFromJson(json)
+                .WriteTo.Sink(new DelegatingSink(e => evt = e))
+                .CreateLogger();
+            log.Information("Destructuring with hard-coded policy {@Input}", new { Foo = "Bar" });
+            var formattedProperty = evt.Properties["Input"].ToString();
+
+            Assert.Equal("\"hardcoded\"", formattedProperty);
+        }
     }
 }

test/TestDummies/DummyHardCodedStringDestructuringPolicy.cs

@@ -0,0 +1,22 @@
+using System;
+using Serilog.Core;
+using Serilog.Events;
+
+namespace TestDummies
+{
+    public class DummyHardCodedStringDestructuringPolicy : IDestructuringPolicy
+    {
+        readonly string _hardCodedString;
+
+        public DummyHardCodedStringDestructuringPolicy(string hardCodedString)
+        {
+            _hardCodedString = hardCodedString ?? throw new ArgumentNullException(nameof(hardCodedString));
+        }
+
+        public bool TryDestructure(object value, ILogEventPropertyValueFactory propertyValueFactory, out LogEventPropertyValue result)
+        {
+            result = new ScalarValue(_hardCodedString);
+            return true;
+        }
+    }
+}

test/TestDummies/DummyLoggerConfigurationExtensions.cs

@@ -109,6 +109,14 @@ public static LoggerConfiguration Dummy(
                 s => new DummyWrappingSink(s),
                 wrappedSinkAction);
         }
-        
+
+        public static LoggerConfiguration WithDummyHardCodedString(
+            this LoggerDestructuringConfiguration loggerDestructuringConfiguration,
+            string hardCodedString
+        )
+        {
+            return loggerDestructuringConfiguration.With(new DummyHardCodedStringDestructuringPolicy(hardCodedString));
+        }
+
     }
 }