No longer rely on static state in ConfigurationReader

src/Serilog.Settings.Configuration/ConfigurationLoggerConfigurationExtensions.cs

@@ -17,7 +17,7 @@
 using Microsoft.Extensions.DependencyModel;
 using Serilog.Configuration;
 using Serilog.Settings.Configuration;
-using System.Reflection;
+using Serilog.Settings.Configuration.Assemblies;
 
 namespace Serilog
 {
@@ -48,10 +48,15 @@ public static LoggerConfiguration Configuration(
         {
             if (configuration == null) throw new ArgumentNullException(nameof(configuration));
 
+            var assemblyFinder = dependencyContext == null
+                ? AssemblyFinder.Auto()
+                : AssemblyFinder.ForDependencyContext(dependencyContext);
+
             return settingConfiguration.Settings(
                 new ConfigurationReader(
-                    configuration,
-                    dependencyContext ?? (Assembly.GetEntryAssembly() != null ? DependencyContext.Default : null)));
+                    configuration.GetSection(DefaultSectionName),
+                    assemblyFinder,
+                    configuration));
         }
 
         /// <summary>
@@ -71,10 +76,15 @@ public static LoggerConfiguration ConfigurationSection(
             if (settingConfiguration == null) throw new ArgumentNullException(nameof(settingConfiguration));
             if (configSection == null) throw new ArgumentNullException(nameof(configSection));
 
+            var assemblyFinder = dependencyContext == null
+                ? AssemblyFinder.Auto()
+                : AssemblyFinder.ForDependencyContext(dependencyContext);
+
             return settingConfiguration.Settings(
                 new ConfigurationReader(
                     configSection,
-                    dependencyContext ?? (Assembly.GetEntryAssembly() != null ? DependencyContext.Default : null)));
+                    assemblyFinder,
+                    configuration: null));
         }
 
         /// <summary>
@@ -93,14 +103,9 @@ public static LoggerConfiguration Configuration(
         {
             if (configuration == null) throw new ArgumentNullException(nameof(configuration));
 
-            if(configurationAssemblySource == ConfigurationAssemblySource.UseLoadedAssemblies)
-            {
-                return Configuration(settingConfiguration, configuration);
-            }
-            else
-            {
-                return settingConfiguration.Settings(new ConfigurationReader(configuration, null));
-            }
+            var assemblyFinder = AssemblyFinder.ForSource(configurationAssemblySource);
+
+            return settingConfiguration.Settings(new ConfigurationReader(configuration.GetSection(DefaultSectionName), assemblyFinder, configuration));
         }
 
         /// <summary>
@@ -119,14 +124,9 @@ public static LoggerConfiguration ConfigurationSection(
             if (settingConfiguration == null) throw new ArgumentNullException(nameof(settingConfiguration));
             if (configSection == null) throw new ArgumentNullException(nameof(configSection));
 
-            if (configurationAssemblySource == ConfigurationAssemblySource.UseLoadedAssemblies)
-            {
-                return Configuration(settingConfiguration, configSection);
-            }
-            else
-            {
-                return settingConfiguration.Settings(new ConfigurationReader(configSection, null));
-            }
+            var assemblyFinder = AssemblyFinder.ForSource(configurationAssemblySource);
+
+            return settingConfiguration.Settings(new ConfigurationReader(configSection, assemblyFinder, configuration: null));
         }
     }
 }

src/Serilog.Settings.Configuration/Settings/Configuration/Assemblies/AssemblyFinder.cs

@@ -0,0 +1,46 @@
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+using Microsoft.Extensions.DependencyModel;
+
+namespace Serilog.Settings.Configuration.Assemblies
+{
+    abstract class AssemblyFinder
+    {
+        public abstract IReadOnlyList<AssemblyName> FindAssembliesContainingName(string nameToFind);
+
+        protected static bool IsCaseInsensitiveMatch(string text, string textToFind)
+        {
+            return text != null && text.ToLowerInvariant().Contains(textToFind.ToLowerInvariant());
+        }
+
+        public static AssemblyFinder Auto()
+        {
+            // Need to check `Assembly.GetEntryAssembly()` first because 
+            // `DependencyContext.Default` throws an exception when `Assembly.GetEntryAssembly()` returns null
+            if (Assembly.GetEntryAssembly() != null && DependencyContext.Default != null)
+            {
+                return new DependencyContextAssemblyFinder(DependencyContext.Default);
+            }
+            return new DllScanningAssemblyFinder();
+        }
+
+        public static AssemblyFinder ForSource(ConfigurationAssemblySource configurationAssemblySource)
+        {
+            switch (configurationAssemblySource)
+            {
+                case ConfigurationAssemblySource.UseLoadedAssemblies:
+                    return Auto();
+                case ConfigurationAssemblySource.AlwaysScanDllFiles:
+                    return new DllScanningAssemblyFinder();
+                default:
+                    throw new ArgumentOutOfRangeException(nameof(configurationAssemblySource), configurationAssemblySource, null);
+            }
+        }
+
+        public static AssemblyFinder ForDependencyContext(DependencyContext dependencyContext)
+        {
+            return new DependencyContextAssemblyFinder(dependencyContext);
+        }
+    }
+}

src/Serilog.Settings.Configuration/Settings/Configuration/Assemblies/DependencyContextAssemblyFinder.cs

@@ -0,0 +1,28 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+using Microsoft.Extensions.DependencyModel;
+
+namespace Serilog.Settings.Configuration.Assemblies
+{
+    sealed class DependencyContextAssemblyFinder : AssemblyFinder
+    {
+        readonly DependencyContext _dependencyContext;
+
+        public DependencyContextAssemblyFinder(DependencyContext dependencyContext)
+        {
+            _dependencyContext = dependencyContext ?? throw new ArgumentNullException(nameof(dependencyContext));
+        }
+
+        public override IReadOnlyList<AssemblyName> FindAssembliesContainingName(string nameToFind)
+        {
+            var query = from library in _dependencyContext.RuntimeLibraries
+                        from assemblyName in library.GetDefaultAssemblyNames(_dependencyContext)
+                        where IsCaseInsensitiveMatch(assemblyName.Name, nameToFind)
+                        select assemblyName;
+
+            return query.ToList().AsReadOnly();
+        }
+    }
+}

src/Serilog.Settings.Configuration/Settings/Configuration/Assemblies/DllScanningAssemblyFinder.cs

@@ -0,0 +1,20 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+
+namespace Serilog.Settings.Configuration.Assemblies
+{
+    sealed class DllScanningAssemblyFinder : AssemblyFinder
+    {
+        public override IReadOnlyList<AssemblyName> FindAssembliesContainingName(string nameToFind)
+        {
+            var query = from outputAssemblyPath in System.IO.Directory.GetFiles(AppDomain.CurrentDomain.BaseDirectory, "*.dll")
+                let assemblyFileName = System.IO.Path.GetFileNameWithoutExtension(outputAssemblyPath)
+                where IsCaseInsensitiveMatch(assemblyFileName, nameToFind)
+                select AssemblyName.GetAssemblyName(outputAssemblyPath);
+
+            return query.ToList().AsReadOnly();
+        }
+    }
+}