Supply services when configuring Serilog inline

Author: nblumhardt

global.json

@@ -1,5 +1,5 @@
 {
   "sdk": {
-    "version": "2.2.105"
+    "version": "3.1.201"
   }
 }

serilog-extensions-hosting.sln.DotSettings

@@ -2,4 +2,6 @@
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=appsettings/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=benaadams/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=destructure/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/UserDictionary/Words/=Enricher/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/UserDictionary/Words/=MEDI/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=Serilog/@EntryIndexedValue">True</s:Boolean></wpf:ResourceDictionary>

src/Serilog.Extensions.Hosting/Extensions/Hosting/NullEnricher.cs

@@ -0,0 +1,28 @@
+// Copyright 2020 Serilog Contributors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+using Serilog.Core;
+using Serilog.Events;
+
+namespace Serilog.Extensions.Hosting
+{
+    // Does nothing, but makes it easy to create an `ILogger` from a Serilog `Logger`
+    // that will not dispose the underlying pipeline when disposed itself.
+    class NullEnricher : ILogEventEnricher
+    {
+        public void Enrich(LogEvent logEvent, ILogEventPropertyFactory propertyFactory)
+        {
+        }
+    }
+}

src/Serilog.Extensions.Hosting/SerilogHostBuilderExtensions.cs

@@ -1,4 +1,4 @@
-// Copyright 2019 Serilog Contributors
+// Copyright 2020 Serilog Contributors
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -13,9 +13,9 @@
 // limitations under the License.
 
 using System;
+using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
-using Microsoft.Extensions.DependencyInjection;
 using Serilog.Extensions.Hosting;
 using Serilog.Extensions.Logging;
 
@@ -26,16 +26,27 @@ namespace Serilog
     /// </summary>
     public static class SerilogHostBuilderExtensions
     {
+        // Used internally to pass information through the container.
+        class RegisteredLogger
+        {
+            public RegisteredLogger(ILogger logger)
+            {
+                Logger = logger;
+            }
+            
+            public ILogger Logger { get; }
+        }
+
         /// <summary>
         /// Sets Serilog as the logging provider.
         /// </summary>
         /// <param name="builder">The host builder to configure.</param>
         /// <param name="logger">The Serilog logger; if not supplied, the static <see cref="Serilog.Log"/> will be used.</param>
         /// <param name="dispose">When <c>true</c>, dispose <paramref name="logger"/> when the framework disposes the provider. If the
-        /// logger is not specified but <paramref name="dispose"/> is <c>true</c>, the <see cref="Log.CloseAndFlush()"/> method will be
-        /// called on the static <see cref="Log"/> class instead.</param>
+        /// logger is not specified but <paramref name="dispose"/> is <c>true</c>, the <see cref="Serilog.Log.CloseAndFlush()"/> method will be
+        /// called on the static <see cref="Serilog.Log"/> class instead.</param>
         /// <param name="providers">A <see cref="LoggerProviderCollection"/> registered in the Serilog pipeline using the
-        /// <c>WriteTo.Providers()</c> configuration method, enabling other <see cref="ILoggerProvider"/>s to receive events. By
+        /// <c>WriteTo.Providers()</c> configuration method, enabling other <see cref="Microsoft.Extensions.Logging.ILoggerProvider"/>s to receive events. By
         /// default, only Serilog sinks will receive events.</param>
         /// <returns>The host builder.</returns>
         public static IHostBuilder UseSerilog(
@@ -71,14 +82,15 @@ public static IHostBuilder UseSerilog(
             return builder;
         }
 
+
         /// <summary>Sets Serilog as the logging provider.</summary>
         /// <remarks>
         /// A <see cref="HostBuilderContext"/> is supplied so that configuration and hosting information can be used.
         /// The logger will be shut down when application services are disposed.
         /// </remarks>
         /// <param name="builder">The host builder to configure.</param>
-        /// <param name="configureLogger">The delegate for configuring the <see cref="LoggerConfiguration" /> that will be used to construct a <see cref="Microsoft.Extensions.Logging.Logger" />.</param>
-        /// <param name="preserveStaticLogger">Indicates whether to preserve the value of <see cref="Log.Logger"/>.</param>
+        /// <param name="configureLogger">The delegate for configuring the <see cref="Serilog.LoggerConfiguration" /> that will be used to construct a <see cref="Serilog.Core.Logger" />.</param>
+        /// <param name="preserveStaticLogger">Indicates whether to preserve the value of <see cref="Serilog.Log.Logger"/>.</param>
         /// <param name="writeToProviders">By default, Serilog does not write events to <see cref="ILoggerProvider"/>s registered through
         /// the Microsoft.Extensions.Logging API. Normally, equivalent Serilog sinks are used in place of providers. Specify
         /// <c>true</c> to write events to all providers.</param>
@@ -91,35 +103,80 @@ public static IHostBuilder UseSerilog(
         {
             if (builder == null) throw new ArgumentNullException(nameof(builder));
             if (configureLogger == null) throw new ArgumentNullException(nameof(configureLogger));
+            return UseSerilog(
+                builder,
+                (hostBuilderContext, services, loggerConfiguration) =>
+                    configureLogger(hostBuilderContext, loggerConfiguration),
+                preserveStaticLogger: preserveStaticLogger,
+                writeToProviders: writeToProviders);
+        }
+
+        /// <summary>Sets Serilog as the logging provider.</summary>
+        /// <remarks>
+        /// A <see cref="HostBuilderContext"/> is supplied so that configuration and hosting information can be used.
+        /// The logger will be shut down when application services are disposed.
+        /// </remarks>
+        /// <param name="builder">The host builder to configure.</param>
+        /// <param name="configureLogger">The delegate for configuring the <see cref="Serilog.LoggerConfiguration" /> that will be used to construct a <see cref="Serilog.Core.Logger" />.</param>
+        /// <param name="preserveStaticLogger">Indicates whether to preserve the value of <see cref="Serilog.Log.Logger"/>.</param>
+        /// <param name="writeToProviders">By default, Serilog does not write events to <see cref="ILoggerProvider"/>s registered through
+        /// the Microsoft.Extensions.Logging API. Normally, equivalent Serilog sinks are used in place of providers. Specify
+        /// <c>true</c> to write events to all providers.</param>
+        /// <returns>The host builder.</returns>
+        public static IHostBuilder UseSerilog(
+            this IHostBuilder builder,
+            Action<HostBuilderContext, IServiceProvider, LoggerConfiguration> configureLogger,
+            bool preserveStaticLogger = false,
+            bool writeToProviders = false)
+        {
+            if (builder == null) throw new ArgumentNullException(nameof(builder));
+            if (configureLogger == null) throw new ArgumentNullException(nameof(configureLogger));
 
             builder.ConfigureServices((context, collection) =>
             {
-                var loggerConfiguration = new LoggerConfiguration();
-
                 LoggerProviderCollection loggerProviders = null;
                 if (writeToProviders)
                 {
                     loggerProviders = new LoggerProviderCollection();
-                    loggerConfiguration.WriteTo.Providers(loggerProviders);
                 }
-
-                configureLogger(context, loggerConfiguration);
-                var logger = loggerConfiguration.CreateLogger();
 
-                ILogger registeredLogger = null;
-                if (preserveStaticLogger)
-                {
-                    registeredLogger = logger;
-                }
-                else
+                collection.AddSingleton(services =>
                 {
-                    // Passing a `null` logger to `SerilogLoggerFactory` results in disposal via
-                    // `Log.CloseAndFlush()`, which additionally replaces the static logger with a no-op.
-                    Log.Logger = logger;
-                }
+                    var loggerConfiguration = new LoggerConfiguration();
+
+                    if (loggerProviders != null)
+                        loggerConfiguration.WriteTo.Providers(loggerProviders);
+            
+                    configureLogger(context, services, loggerConfiguration);
+                    var logger = loggerConfiguration.CreateLogger();
+
+                    return new RegisteredLogger(logger);
+                });
 
+                collection.AddSingleton(services =>
+                {
+                    // How can we register the logger, here, but not have MEDI dispose it?
+                    // Using the `NullEnricher` hack to prevent disposal.
+                    var logger = services.GetRequiredService<RegisteredLogger>().Logger;
+                    return logger.ForContext(new NullEnricher());
+                });
+                
                 collection.AddSingleton<ILoggerFactory>(services =>
                 {
+                    var logger = services.GetRequiredService<RegisteredLogger>().Logger;
+                    
+                    ILogger registeredLogger = null;
+                    if (preserveStaticLogger)
+                    {
+                        registeredLogger = logger;
+                    }
+                    else
+                    {
+                        // Passing a `null` logger to `SerilogLoggerFactory` results in disposal via
+                        // `Log.CloseAndFlush()`, which additionally replaces the static logger with a no-op.
+                        Log.Logger = logger;
+                    }
+
                     var factory = new SerilogLoggerFactory(registeredLogger, true, loggerProviders);
 
                     if (writeToProviders)
@@ -130,8 +187,8 @@ public static IHostBuilder UseSerilog(
 
                     return factory;
                 });
-
-                ConfigureServices(collection, logger);
+                
+                ConfigureServices(collection, null);
             });
             return builder;
         }