Add support for .Destructure.XXX() methods

Supports Serilog "native" non-generic simple  methods : 
- `ToMaximumCollectionCount`
- `ToMaximumDepth`
- `ToMaximumStringLength`

and any *extension method* for `LoggerDestructuringConfiguration`

This should fix serilog#1172

src/Serilog/Settings/KeyValuePairs/CallableConfigurationMethodFinder.cs

@@ -27,9 +27,30 @@ internal static LoggerConfiguration FromLogContext(LoggerEnrichmentConfiguration
         {
             return loggerEnrichmentConfiguration.FromLogContext();
         }
-
         static readonly MethodInfo SurrogateFromLogContextConfigurationMethod = typeof(CallableConfigurationMethodFinder).GetTypeInfo().DeclaredMethods.Single(m => m.Name == nameof(FromLogContext));
 
+        internal static LoggerConfiguration ToMaximumCollectionCount(LoggerDestructuringConfiguration loggerDestructuringConfiguration,
+            int maximumCollectionCount)
+        {
+            return loggerDestructuringConfiguration.ToMaximumCollectionCount(maximumCollectionCount);
+        }
+        static readonly MethodInfo SurrogateFromDestructureToMaximumCollectionCountConfigurationMethod = typeof(CallableConfigurationMethodFinder).GetTypeInfo().DeclaredMethods.Single(m => m.Name == nameof(ToMaximumCollectionCount));
+
+        internal static LoggerConfiguration ToMaximumDepth(LoggerDestructuringConfiguration loggerDestructuringConfiguration,
+            int maximumDestructuringDepth)
+        {
+            return loggerDestructuringConfiguration.ToMaximumDepth(maximumDestructuringDepth);
+        }
+        static readonly MethodInfo SurrogateFromDestructureToMaximumDepthConfigurationMethod = typeof(CallableConfigurationMethodFinder).GetTypeInfo().DeclaredMethods.Single(m => m.Name == nameof(ToMaximumDepth));
+
+        internal static LoggerConfiguration ToMaximumStringLength(LoggerDestructuringConfiguration loggerDestructuringConfiguration,
+            int maximumStringLength)
+        {
+            return loggerDestructuringConfiguration.ToMaximumStringLength(maximumStringLength);
+        }
+        static readonly MethodInfo SurrogateFromDestructureToMaximumStringLengthConfigurationMethod = typeof(CallableConfigurationMethodFinder).GetTypeInfo().DeclaredMethods.Single(m => m.Name == nameof(ToMaximumStringLength));
+
+
         internal static IList<MethodInfo> FindConfigurationMethods(IEnumerable<Assembly> configurationAssemblies, Type configType)
         {
             var methods = configurationAssemblies
@@ -46,6 +67,14 @@ internal static IList<MethodInfo> FindConfigurationMethods(IEnumerable<Assembly>
             if (configType == typeof(LoggerEnrichmentConfiguration))
                 methods.Add(SurrogateFromLogContextConfigurationMethod);
 
+            // Some of the useful Destructure configuration methods are defined as methods rather than extension methods
+            if (configType == typeof(LoggerDestructuringConfiguration))
+            {
+                methods.Add(SurrogateFromDestructureToMaximumCollectionCountConfigurationMethod);
+                methods.Add(SurrogateFromDestructureToMaximumDepthConfigurationMethod);
+                methods.Add(SurrogateFromDestructureToMaximumStringLengthConfigurationMethod);
+            }
+
             return methods;
         }
     }

src/Serilog/Settings/KeyValuePairs/KeyValuePairSettings.cs

@@ -34,12 +34,13 @@ class KeyValuePairSettings : ILoggerSettings
         const string EnrichWithDirective = "enrich";
         const string EnrichWithPropertyDirective = "enrich:with-property";
         const string FilterDirective = "filter";
+        const string DestructureDirective = "destructure";
 
         const string UsingDirectiveFullFormPrefix = "using:";
         const string EnrichWithPropertyDirectivePrefix = "enrich:with-property:";
         const string MinimumLevelOverrideDirectivePrefix = "minimum-level:override:";
 
-        const string CallableDirectiveRegex = @"^(?<directive>audit-to|write-to|enrich|filter):(?<method>[A-Za-z0-9]*)(\.(?<argument>[A-Za-z0-9]*)){0,1}$";
+        const string CallableDirectiveRegex = @"^(?<directive>audit-to|write-to|enrich|filter|destructure):(?<method>[A-Za-z0-9]*)(\.(?<argument>[A-Za-z0-9]*)){0,1}$";
         const string LevelSwitchDeclarationDirectiveRegex = @"^level-switch:(?<switchName>.*)$";
         const string LevelSwitchNameRegex = @"^\$[A-Za-z]+[A-Za-z0-9]*$";
 
@@ -53,23 +54,26 @@ class KeyValuePairSettings : ILoggerSettings
             MinimumLevelControlledByDirective,
             EnrichWithPropertyDirective,
             EnrichWithDirective,
-            FilterDirective
+            FilterDirective,
+            DestructureDirective
         };
 
         static readonly Dictionary<string, Type> CallableDirectiveReceiverTypes = new Dictionary<string, Type>
         {
             ["audit-to"] = typeof(LoggerAuditSinkConfiguration),
             ["write-to"] = typeof(LoggerSinkConfiguration),
             ["enrich"] = typeof(LoggerEnrichmentConfiguration),
-            ["filter"] = typeof(LoggerFilterConfiguration)
+            ["filter"] = typeof(LoggerFilterConfiguration),
+            ["destructure"] = typeof(LoggerDestructuringConfiguration),
         };
 
         static readonly Dictionary<Type, Func<LoggerConfiguration, object>> CallableDirectiveReceivers = new Dictionary<Type, Func<LoggerConfiguration, object>>
         {
             [typeof(LoggerAuditSinkConfiguration)] = lc => lc.AuditTo,
             [typeof(LoggerSinkConfiguration)] = lc => lc.WriteTo,
             [typeof(LoggerEnrichmentConfiguration)] = lc => lc.Enrich,
-            [typeof(LoggerFilterConfiguration)] = lc => lc.Filter
+            [typeof(LoggerFilterConfiguration)] = lc => lc.Filter,
+            [typeof(LoggerDestructuringConfiguration)] = lc => lc.Destructure,
         };
 
         readonly IReadOnlyDictionary<string, string> _settings;

test/Serilog.Tests/Settings/CallableConfigurationMethodFinderTests.cs

@@ -26,5 +26,24 @@ public void FindsEnricherSpecificConfigurationMethods()
             Assert.Contains("FromLogContext", eventEnrichers);
             Assert.Contains("WithDummyThreadId", eventEnrichers);
         }
+
+        [Fact]
+        public void FindsDestructureSpecificConfigurationMethods()
+        {
+            var destructuringMethods = CallableConfigurationMethodFinder
+                .FindConfigurationMethods(new[]
+                {
+                    typeof(Log).GetTypeInfo().Assembly,
+                    typeof(DummyThreadIdEnricher).GetTypeInfo().Assembly,
+                }, typeof(LoggerDestructuringConfiguration))
+                .Select(m => m.Name)
+                .Distinct()
+                .ToList();
+
+            Assert.Contains(nameof(LoggerDestructuringConfiguration.ToMaximumCollectionCount), destructuringMethods);
+            Assert.Contains(nameof(LoggerDestructuringConfiguration.ToMaximumDepth), destructuringMethods);
+            Assert.Contains(nameof(LoggerDestructuringConfiguration.ToMaximumStringLength), destructuringMethods);
+            Assert.Contains(nameof(DummyLoggerConfigurationExtensions.WithDummyHardCodedString), destructuringMethods);
+        }
     }
 }

test/Serilog.Tests/Settings/KeyValuePairSettingsTests.cs

@@ -381,5 +381,96 @@ public void SinksAreConfiguredWithStaticMember()
 
             Assert.Equal(ConsoleThemes.Theme1, DummyConsoleSink.Theme);
         }
+
+        [Fact]
+        public void DestructuringToMaximumDepthIsApplied()
+        {
+            LogEvent evt = null;
+            var log = new LoggerConfiguration()
+                .ReadFrom.KeyValuePairs(new Dictionary<string, string>
+                {
+                    ["destructure:ToMaximumDepth.maximumDestructuringDepth"] = "3"
+                })
+                .WriteTo.Sink(new DelegatingSink(e => evt = e))
+                .CreateLogger();
+
+            var nestedObject = new
+            {
+                A = new
+                {
+                    B = new
+                    {
+                        C = new
+                        {
+                            D = "F"
+                        }
+                    }
+                }
+            };
+
+            log.Information("Destructuring a big graph {@DeeplyNested}", nestedObject);
+            var formattedProperty = evt.Properties["DeeplyNested"].ToString();
+
+            Assert.Contains("C", formattedProperty);
+            Assert.DoesNotContain("D", formattedProperty);
+        }
+
+        [Fact]
+        public void DestructuringToMaximumStringLengthIsApplied()
+        {
+            LogEvent evt = null;
+            var log = new LoggerConfiguration()
+                .ReadFrom.KeyValuePairs(new Dictionary<string, string>
+                {
+                    ["destructure:ToMaximumStringLength.maximumStringLength"] = "3"
+                })
+                .WriteTo.Sink(new DelegatingSink(e => evt = e))
+                .CreateLogger();
+
+            log.Information("Destructuring a long string {@LongString}", "ABCDEFGH");
+            var formattedProperty = evt.Properties["LongString"].ToString();
+
+            Assert.Equal("\"AB…\"", formattedProperty);
+        }
+
+        [Fact]
+        public void DestructuringToMaximumCollectionCountIsApplied()
+        {
+            LogEvent evt = null;
+            var log = new LoggerConfiguration()
+                .ReadFrom.KeyValuePairs(new Dictionary<string, string>
+                {
+                    ["destructure:ToMaximumCollectionCount.maximumCollectionCount"] = "3"
+                })
+                .WriteTo.Sink(new DelegatingSink(e => evt = e))
+                .CreateLogger();
+
+            var collection = new[] { 1, 2, 3, 4, 5, 6 };
+            log.Information("Destructuring a big collection {@BigCollection}", collection);
+            var formattedProperty = evt.Properties["BigCollection"].ToString();
+
+            Assert.Contains("3", formattedProperty);
+            Assert.DoesNotContain("4", formattedProperty);
+        }
+
+        [Fact]
+        public void DestructuringWithCustomExtensionMethodIsApplied()
+        {
+            LogEvent evt = null;
+            var log = new LoggerConfiguration()
+                .ReadFrom.KeyValuePairs(new Dictionary<string, string>
+                {
+                    ["using:TestDummies"] = typeof(DummyLoggerConfigurationExtensions).GetTypeInfo().Assembly.FullName,
+                    ["destructure:WithDummyHardCodedString.hardCodedString"] = "hardcoded"
+                })
+                .WriteTo.Sink(new DelegatingSink(e => evt = e))
+                .CreateLogger();
+
+            log.Information("Destructuring a big collection {@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

@@ -86,5 +86,13 @@ public static LoggerConfiguration DummyWrap(
                 logEventLevel,
                 levelSwitch);
         }
+
+        public static LoggerConfiguration WithDummyHardCodedString(
+            this LoggerDestructuringConfiguration loggerDestructuringConfiguration,
+            string hardCodedString
+        )
+        {
+            return loggerDestructuringConfiguration.With(new DummyHardCodedStringDestructuringPolicy(hardCodedString));
+        }
     }
 }