confing binding and config section hinting

Author: MV10

README.md

@@ -91,3 +91,37 @@ For example, to set the minimum log level using the _Windows_ command prompt:
 set Serilog:MinimumLevel=Debug
 dotnet run
 ```
+
+### Nested configuration sections
+
+Some Serilog packages require a reference to a logger configuration object. These must be "hinted" by appending a `>` character to the end of the argument name. The sample program in this project illustrates this with the following entry configuring the _Serilog.Sinks.Async_ package to wrap the _Serilog.Sinks.File_ package.
+
+Note the `configure>` parameter name with the trailing hint character:
+
+```json
+"WriteTo:Async": {
+  "Name": "Async",
+  "Args": {
+    "configure>": [
+      {
+        "Name": "File",
+        "Args": {
+          "path": "%TEMP%\\Logs\\serilog-configuration-sample.txt",
+          "outputTemplate": "{Timestamp:o} [{Level:u3}] ({Application}/{MachineName}/{ThreadId}) {Message}{NewLine}{Exception}"
+        }
+      }
+    ]
+  }
+},
+```
+
+### IConfiguration parameter
+
+If a Serilog package requires additional external configuration information (for example, access to a `ConnectionStrings` section, which would be outside of the `Serilog` section), the sink should include an `IConfiguration` parameter in the configuration extension method. This package will automatically populate that parameter. It should not be declared in the argument list in the configuration source.
+
+### Complex parameter value binding
+
+When the configuration specifies a discrete value for a parameter (such as a string literal), the package will attempt to convert that value to the target method's declared CLR type of the parameter. Additional explicit handling is provided for parsing strings to `Uri` and `TimeSpan` objects and `enum` elements.
+
+If the parameter value is not a discrete value, the package will use the configuration binding system provided by _Microsoft.Extensions.Options.ConfigurationExtensions_ to attempt to populate the parameter. Almost anything that can be bound by `IConfiguration.Get<T>` should work with this package. An example of this is the optional `List<Column>` parameter used to configure the .NET Standard version of the _Serilog.Sinks.MSSqlServer_ package.
+

sample/Sample/appsettings.json

@@ -11,7 +11,7 @@
     "WriteTo:Sublogger": {
       "Name": "Logger",
       "Args": {
-        "configureLogger": {
+        "configureLogger>": {
           "WriteTo": [
             {
               "Name": "Console",
@@ -28,7 +28,7 @@
     "WriteTo:Async": {
       "Name": "Async",
       "Args": {
-        "configure": [
+        "configure>": [
           {
             "Name": "File",
             "Args": {

src/Serilog.Settings.Configuration/Serilog.Settings.Configuration.csproj

@@ -17,6 +17,8 @@
     <PackageProjectUrl>https://github.com/serilog/serilog-settings-configuration</PackageProjectUrl>
     <PackageLicenseUrl>https://www.apache.org/licenses/LICENSE-2.0</PackageLicenseUrl>
     <RootNamespace>Serilog</RootNamespace>
+    <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
+    <Version>3.0.0.002</Version>
   </PropertyGroup>
 
   <ItemGroup>
@@ -26,10 +28,12 @@
 
   <ItemGroup Condition="'$(TargetFramework)' == 'net451'">
     <PackageReference Include="Microsoft.Extensions.Configuration.Abstractions" Version="1.1.2" />
+    <PackageReference Include="Microsoft.Extensions.Options.ConfigurationExtensions" Version="1.1.2" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
     <PackageReference Include="Microsoft.Extensions.Configuration.Abstractions" Version="2.0.1" />
+    <PackageReference Include="Microsoft.Extensions.Options.ConfigurationExtensions" Version="2.0.0" />
   </ItemGroup>
 
 </Project>

src/Serilog.Settings.Configuration/Settings/Configuration/BoundArgumentValue.cs

@@ -0,0 +1,22 @@
+using Microsoft.Extensions.Configuration;
+using Serilog.Core;
+using System;
+using System.Collections.Generic;
+
+namespace Serilog.Settings.Configuration
+{
+    class BoundArgumentValue : IConfigurationArgumentValue
+    {
+        readonly IConfigurationSection section;
+
+        public BoundArgumentValue(IConfigurationSection section)
+        {
+            this.section = section;
+        }
+
+        public object ConvertTo(Type toType, IReadOnlyDictionary<string, LoggingLevelSwitch> declaredLevelSwitches)
+        {
+            return section.Get(toType);
+        }
+    }
+}

src/Serilog.Settings.Configuration/Settings/Configuration/ConfigurationReader.cs

@@ -19,6 +19,7 @@ namespace Serilog.Settings.Configuration
     class ConfigurationReader : IConfigurationReader
     {
         const string LevelSwitchNameRegex = @"^\$[A-Za-z]+[A-Za-z0-9]*$";
+        const string ConfigSectionHintChar = ">";
 
         readonly IConfigurationSection _configuration;
         readonly DependencyContext _dependencyContext;
@@ -209,7 +210,7 @@ internal ILookup<string, Dictionary<string, IConfigurationArgumentValue>> GetMet
                  let name = GetSectionName(child)
                  let callArgs = (from argument in child.GetSection("Args").GetChildren()
                                  select new {
-                                     Name = argument.Key,
+                                     Name = argument.Key.Replace(ConfigSectionHintChar, string.Empty),
                                      Value = GetArgumentValue(argument) }).ToDictionary(p => p.Name, p => p.Value)
                  select new { Name = name, Args = callArgs }))
                      .ToLookup(p => p.Name, p => p.Args);
@@ -225,7 +226,14 @@ IConfigurationArgumentValue GetArgumentValue(IConfigurationSection argumentSecti
                 }
                 else
                 {
-                    argumentValue = new ConfigurationSectionArgumentValue(new ConfigurationReader(argumentSection, _configurationAssemblies, _dependencyContext));
+                    if(argumentSection.Key.EndsWith(ConfigSectionHintChar))
+                    {
+                        argumentValue = new ConfigurationSectionArgumentValue(new ConfigurationReader(argumentSection, _configurationAssemblies, _dependencyContext));
+                    }
+                    else
+                    {
+                        argumentValue = new BoundArgumentValue(argumentSection);
+                    }
                 }
 
                 return argumentValue;