Do not access "Serilog" sub-section when calling ReadFrom.ConfigSection

fixes #143 where we are trying to read a subsection of config section passed as parameter

Author: tsimbalar

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

@@ -35,9 +35,10 @@ public ConfigurationReader(IConfiguration configuration, DependencyContext depen
 
         // Generally the initial call should use IConfiguration rather than IConfigurationSection, otherwise
         // IConfiguration parameters in the target methods will not be populated.
-        ConfigurationReader(IConfigurationSection configSection, DependencyContext dependencyContext)
+        public ConfigurationReader(IConfigurationSection configSection, DependencyContext dependencyContext)
         {
-            _section = configSection ?? throw new ArgumentNullException(nameof(configSection));
+            _configuration = configSection ?? throw new ArgumentNullException(nameof(configSection));
+            _section = configSection;
             _dependencyContext = dependencyContext;
             _configurationAssemblies = LoadConfigurationAssemblies();
         }

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

@@ -1,5 +1,7 @@
-using System;
+using System;
 using Microsoft.Extensions.Configuration;
+using Serilog.Events;
+using Serilog.Settings.Configuration.Tests.Support;
 using Xunit;
 
 namespace Serilog.Settings.Configuration.Tests
@@ -14,5 +16,34 @@ public void ReadFromConfigurationShouldNotThrowOnEmptyConfiguration()
             // should not throw
             act();
         }
+
+        [Fact]
+        [Trait("BugFix", "https://github.com/serilog/serilog-settings-configuration/issues/143")]
+        public void ReadFromConfigurationSectionReadsFromAnArbitrarySection()
+        {
+            LogEvent evt = null;
+
+            var json = @"{
+		        ""NotSerilog"": {            
+			        ""Properties"": {
+				        ""App"": ""Test""
+			        }
+		        }
+	        }";
+
+            var config = new ConfigurationBuilder()
+                .AddJsonString(json)
+                .Build();
+
+            var log = new LoggerConfiguration()
+                .ReadFrom.ConfigurationSection(config.GetSection("NotSerilog"))
+                .WriteTo.Sink(new DelegatingSink(e => evt = e))
+                .CreateLogger();
+
+            log.Information("Has a test property");
+
+            Assert.NotNull(evt);
+            Assert.Equal("Test", evt.Properties["App"].LiteralValue());
+        }
     }
 }