Load assembly event

src/NLog/Config/AssemblyLoadingEventArgs.cs

@@ -0,0 +1,58 @@
+// 
+// Copyright (c) 2004-2016 Jaroslaw Kowalski <jaak@jkowalski.net>, Kim Christensen, Julian Verdurmen
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without 
+// modification, are permitted provided that the following conditions 
+// are met:
+// 
+// * Redistributions of source code must retain the above copyright notice, 
+//   this list of conditions and the following disclaimer. 
+// 
+// * Redistributions in binary form must reproduce the above copyright notice,
+//   this list of conditions and the following disclaimer in the documentation
+//   and/or other materials provided with the distribution. 
+// 
+// * Neither the name of Jaroslaw Kowalski nor the names of its 
+//   contributors may be used to endorse or promote products derived from this
+//   software without specific prior written permission. 
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
+// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
+// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF 
+// THE POSSIBILITY OF SUCH DAMAGE.
+// 
+
+using System;
+using System.ComponentModel;
+using System.Reflection;
+
+namespace NLog.Config
+{
+    /// <summary>
+    /// An assembly is trying to load. 
+    /// </summary>
+    public class AssemblyLoadingEventArgs : CancelEventArgs
+    {/// <summary>
+     /// New event args
+     /// </summary>
+     /// <param name="assembly"></param>
+        public AssemblyLoadingEventArgs(Assembly assembly)
+        {
+            Assembly = assembly;
+        }
+
+        /// <summary>
+        /// The assembly that is trying to load.
+        /// </summary>
+        public Assembly Assembly { get; private set; }
+    }
+}

src/NLog/Config/ConfigurationItemFactory.cs

@@ -50,6 +50,8 @@ namespace NLog.Config
 
     /// <summary>
     /// Provides registration information for named items (targets, layouts, layout renderers, etc.) managed by NLog.
+    /// 
+    /// Everything of an assembly could be loaded by <see cref="RegisterItemsFromAssembly(System.Reflection.Assembly)"/>
     /// </summary>
     public class ConfigurationItemFactory
     {
@@ -66,6 +68,11 @@ public class ConfigurationItemFactory
 
         private IJsonSerializer jsonSerializer = DefaultJsonSerializer.Instance;
 
+        /// <summary>
+        /// Called before the assembly will be loaded.
+        /// </summary>
+        public static event EventHandler<AssemblyLoadingEventArgs> AssemblyLoading;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="ConfigurationItemFactory"/> class.
         /// </summary>
@@ -205,6 +212,8 @@ public IJsonSerializer JsonSerializer
             get { return this.conditionMethods; }
         }
 
+
+
         /// <summary>
         /// Registers named items from the assembly.
         /// </summary>
@@ -221,6 +230,17 @@ public void RegisterItemsFromAssembly(Assembly assembly)
         /// <param name="itemNamePrefix">Item name prefix.</param>
         public void RegisterItemsFromAssembly(Assembly assembly, string itemNamePrefix)
         {
+            if (AssemblyLoading != null)
+            {
+                var args = new AssemblyLoadingEventArgs(assembly);
+                AssemblyLoading.Invoke(this,args);
+                if (args.Cancel)
+                {
+                    InternalLogger.Info("Loading assembly '{0}' is canceled", assembly.FullName);
+                    return;
+                }
+            }
+
             InternalLogger.Debug("ScanAssembly('{0}')", assembly.FullName);
             var typesToScan = assembly.SafeGetTypes();
             PreloadAssembly(typesToScan);
@@ -233,6 +253,10 @@ public void RegisterItemsFromAssembly(Assembly assembly, string itemNamePrefix)
         /// <summary>
         /// Call Preload for NLogPackageLoader
         /// </summary>
+        /// <remarks>
+        /// Every package could implement a class "NLogPackageLoader" (namespace not important) with the public static method "Preload" (no arguments)
+        /// This method will be called just before registering all items in the assembly.
+        /// </remarks>
         /// <param name="typesToScan"></param>
         public void PreloadAssembly(Type[] typesToScan)
         {
@@ -245,7 +269,7 @@ public void PreloadAssembly(Type[] typesToScan)
         }
 
         /// <summary>
-        /// Call Preload method for <paramref name="type"/>. The Preload method must be static.
+        /// Call the Preload method for <paramref name="type"/>. The Preload method must be static.
         /// </summary>
         /// <param name="type"></param>
         private static void CallPreload(Type type)

src/NLog/NLog.Xamarin.Android.csproj

@@ -82,6 +82,7 @@
     <Compile Include="Config\AdvancedAttribute.cs" />
     <Compile Include="Config\AppDomainFixedOutputAttribute.cs" />
     <Compile Include="Config\ArrayParameterAttribute.cs" />
+    <Compile Include="Config\AssemblyLoadingEventArgs.cs" />
     <Compile Include="Config\ConfigSectionHandler.cs" />
     <Compile Include="Config\ConfigurationItemCreator.cs" />
     <Compile Include="Config\ConfigurationItemFactory.cs" />

src/NLog/NLog.Xamarin.iOS.csproj

@@ -79,6 +79,7 @@
     <Compile Include="Config\AdvancedAttribute.cs" />
     <Compile Include="Config\AppDomainFixedOutputAttribute.cs" />
     <Compile Include="Config\ArrayParameterAttribute.cs" />
+    <Compile Include="Config\AssemblyLoadingEventArgs.cs" />
     <Compile Include="Config\ConfigSectionHandler.cs" />
     <Compile Include="Config\ConfigurationItemCreator.cs" />
     <Compile Include="Config\ConfigurationItemFactory.cs" />

src/NLog/NLog.doc.csproj

@@ -92,6 +92,7 @@
     <Compile Include="Config\AdvancedAttribute.cs" />
     <Compile Include="Config\AppDomainFixedOutputAttribute.cs" />
     <Compile Include="Config\ArrayParameterAttribute.cs" />
+    <Compile Include="Config\AssemblyLoadingEventArgs.cs" />
     <Compile Include="Config\ConfigSectionHandler.cs" />
     <Compile Include="Config\ConfigurationItemCreator.cs" />
     <Compile Include="Config\ConfigurationItemFactory.cs" />

src/NLog/NLog.mono.csproj

@@ -98,6 +98,7 @@
     <Compile Include="Config\AdvancedAttribute.cs" />
     <Compile Include="Config\AppDomainFixedOutputAttribute.cs" />
     <Compile Include="Config\ArrayParameterAttribute.cs" />
+    <Compile Include="Config\AssemblyLoadingEventArgs.cs" />
     <Compile Include="Config\ConfigSectionHandler.cs" />
     <Compile Include="Config\ConfigurationItemCreator.cs" />
     <Compile Include="Config\ConfigurationItemFactory.cs" />

src/NLog/NLog.netfx35.csproj

@@ -92,6 +92,7 @@
     <Compile Include="Config\AdvancedAttribute.cs" />
     <Compile Include="Config\AppDomainFixedOutputAttribute.cs" />
     <Compile Include="Config\ArrayParameterAttribute.cs" />
+    <Compile Include="Config\AssemblyLoadingEventArgs.cs" />
     <Compile Include="Config\ConfigSectionHandler.cs" />
     <Compile Include="Config\ConfigurationItemCreator.cs" />
     <Compile Include="Config\ConfigurationItemFactory.cs" />

src/NLog/NLog.netfx40.csproj

@@ -92,6 +92,7 @@
     <Compile Include="Config\AdvancedAttribute.cs" />
     <Compile Include="Config\AppDomainFixedOutputAttribute.cs" />
     <Compile Include="Config\ArrayParameterAttribute.cs" />
+    <Compile Include="Config\AssemblyLoadingEventArgs.cs" />
     <Compile Include="Config\ConfigSectionHandler.cs" />
     <Compile Include="Config\ConfigurationItemCreator.cs" />
     <Compile Include="Config\ConfigurationItemFactory.cs" />

src/NLog/NLog.netfx45.csproj

@@ -98,6 +98,7 @@
     <Compile Include="Config\AdvancedAttribute.cs" />
     <Compile Include="Config\AppDomainFixedOutputAttribute.cs" />
     <Compile Include="Config\ArrayParameterAttribute.cs" />
+    <Compile Include="Config\AssemblyLoadingEventArgs.cs" />
     <Compile Include="Config\ConfigSectionHandler.cs" />
     <Compile Include="Config\ConfigurationItemCreator.cs" />
     <Compile Include="Config\ConfigurationItemFactory.cs" />

src/NLog/NLog.sl4.csproj

@@ -99,6 +99,7 @@
     <Compile Include="Config\AdvancedAttribute.cs" />
     <Compile Include="Config\AppDomainFixedOutputAttribute.cs" />
     <Compile Include="Config\ArrayParameterAttribute.cs" />
+    <Compile Include="Config\AssemblyLoadingEventArgs.cs" />
     <Compile Include="Config\ConfigSectionHandler.cs" />
     <Compile Include="Config\ConfigurationItemCreator.cs" />
     <Compile Include="Config\ConfigurationItemFactory.cs" />

src/NLog/NLog.sl5.csproj

@@ -96,6 +96,7 @@
     <Compile Include="Config\AdvancedAttribute.cs" />
     <Compile Include="Config\AppDomainFixedOutputAttribute.cs" />
     <Compile Include="Config\ArrayParameterAttribute.cs" />
+    <Compile Include="Config\AssemblyLoadingEventArgs.cs" />
     <Compile Include="Config\ConfigSectionHandler.cs" />
     <Compile Include="Config\ConfigurationItemCreator.cs" />
     <Compile Include="Config\ConfigurationItemFactory.cs" />

src/NLog/NLog.wp7.csproj

@@ -95,6 +95,7 @@
     <Compile Include="Config\AdvancedAttribute.cs" />
     <Compile Include="Config\AppDomainFixedOutputAttribute.cs" />
     <Compile Include="Config\ArrayParameterAttribute.cs" />
+    <Compile Include="Config\AssemblyLoadingEventArgs.cs" />
     <Compile Include="Config\ConfigSectionHandler.cs" />
     <Compile Include="Config\ConfigurationItemCreator.cs" />
     <Compile Include="Config\ConfigurationItemFactory.cs" />

src/NLog/NLog.wp71.csproj

@@ -95,6 +95,7 @@
     <Compile Include="Config\AdvancedAttribute.cs" />
     <Compile Include="Config\AppDomainFixedOutputAttribute.cs" />
     <Compile Include="Config\ArrayParameterAttribute.cs" />
+    <Compile Include="Config\AssemblyLoadingEventArgs.cs" />
     <Compile Include="Config\ConfigSectionHandler.cs" />
     <Compile Include="Config\ConfigurationItemCreator.cs" />
     <Compile Include="Config\ConfigurationItemFactory.cs" />

src/NLog/NLog.wp8.csproj

@@ -120,6 +120,7 @@
     <Compile Include="Config\AdvancedAttribute.cs" />
     <Compile Include="Config\AppDomainFixedOutputAttribute.cs" />
     <Compile Include="Config\ArrayParameterAttribute.cs" />
+    <Compile Include="Config\AssemblyLoadingEventArgs.cs" />
     <Compile Include="Config\ConfigSectionHandler.cs" />
     <Compile Include="Config\ConfigurationItemCreator.cs" />
     <Compile Include="Config\ConfigurationItemFactory.cs" />

tests/NLog.UnitTests/Config/ExtensionTests.cs

@@ -31,9 +31,11 @@
 // THE POSSIBILITY OF SUCH DAMAGE.
 // 
 
+using System;
 using System.Text.RegularExpressions;
 using NLog.Common;
 using NLog.Config;
+using Xunit.Extensions;
 
 namespace NLog.UnitTests.Config
 {
@@ -371,7 +373,11 @@ public void CustomXmlNamespaceTest()
         [Fact]
         public void Extension_should_be_auto_loaded_when_following_NLog_dll_format()
         {
-            var configuration = CreateConfigurationFromString(@"
+            try
+            {
+
+
+                var configuration = CreateConfigurationFromString(@"
 <nlog throwExceptions='true'>
     <targets>
         <target name='t' type='AutoLoadTarget' />
@@ -383,8 +389,68 @@ public void Extension_should_be_auto_loaded_when_following_NLog_dll_format()
     </rules>
 </nlog>");
 
-            var autoLoadedTarget = configuration.FindTargetByName("t");
-            Assert.Equal("NLogAutloadExtension.AutoLoadTarget", autoLoadedTarget.GetType().FullName);
+                var autoLoadedTarget = configuration.FindTargetByName("t");
+                Assert.Equal("NLogAutloadExtension.AutoLoadTarget", autoLoadedTarget.GetType().FullName);
+            }
+            finally
+            {
+                ConfigurationItemFactory.Default.Clear();
+                ConfigurationItemFactory.Default = null; //build new factory next time
+            }
+        }
+
+        [Theory]
+        [InlineData(true)]
+        [InlineData(false)]
+        public void Extension_loading_could_be_canceled(bool cancel)
+        {
+
+            EventHandler<AssemblyLoadingEventArgs> onAssemblyLoading = (sender, e) =>
+            {
+                if (e.Assembly.FullName.Contains("NLogAutloadExtension"))
+                {
+                    e.Cancel = cancel;
+                }
+            };
+
+            try
+            {
+                ConfigurationItemFactory.Default = null; //build new factory next time
+                ConfigurationItemFactory.AssemblyLoading += onAssemblyLoading;
+
+                var configuration = CreateConfigurationFromString(@"
+<nlog throwExceptions='false'>
+    <targets>
+        <target name='t' type='AutoLoadTarget' />
+    </targets>
+
+    <rules>
+      <logger name='*' writeTo='t'>
+      </logger>
+    </rules>
+</nlog>");
+
+
+
+                var autoLoadedTarget = configuration.FindTargetByName("t");
+
+                if (cancel)
+                {
+                    Assert.Null(autoLoadedTarget);
+                }
+                else
+                {
+                    Assert.Equal("NLogAutloadExtension.AutoLoadTarget", autoLoadedTarget.GetType().FullName);
+                }
+            }
+            finally
+            {
+                //cleanup
+                ConfigurationItemFactory.AssemblyLoading -= onAssemblyLoading;
+                ConfigurationItemFactory.Default.Clear();
+                ConfigurationItemFactory.Default = null; //build new factory next time
+
+            }
         }
 
         [Fact]
@@ -401,7 +467,7 @@ public void Extensions_NLogPackageLoader_should_beCalled()
                 var fact = ConfigurationItemFactory.Default;
 
                 //also throw exceptions 
-               LogManager.Configuration = CreateConfigurationFromString(@"
+                LogManager.Configuration = CreateConfigurationFromString(@"
 <nlog throwExceptions='true'>
 
 </nlog>");