Add option to blacklist MSIE engine.

Author: Daniel15

src/React.Core/IReactSiteConfiguration.cs

@@ -99,5 +99,15 @@ public interface IReactSiteConfiguration
 		/// Defaults to <c>25</c>.
 		/// </summary>
 		IReactSiteConfiguration SetMaxEngines(int? maxEngines);
+
+		/// <summary>
+		/// Gets or sets whether the MSIE engine should be used if V8 is unavailable.
+		/// </summary>
+		bool AllowMsieEngine { get; set; }
+		/// <summary>
+		/// Sets whether the MSIE engine should be used if V8 is unavailable.
+		/// </summary>
+		/// <returns></returns>
+		IReactSiteConfiguration SetAllowMsieEngine(bool allowMsieEngine);
 	}
 }

src/React.Core/JavaScriptEngineFactory.cs

@@ -6,6 +6,7 @@
 using System.Linq;
 using System.Threading;
 using JavaScriptEngineSwitcher.Core;
+using JavaScriptEngineSwitcher.Msie;
 using JavaScriptEngineSwitcher.V8;
 using JSPool;
 using React.Exceptions;
@@ -72,7 +73,7 @@ IFileSystem fileSystem
 		{
 			_config = config;
 			_fileSystem = fileSystem;
-			_factory = GetFactory(availableFactories);
+			_factory = GetFactory(availableFactories, config.AllowMsieEngine);
 			if (_config.ReuseJavaScriptEngines)
 			{
 				_pool = CreatePool();
@@ -197,7 +198,7 @@ public virtual void ReturnEngineToPool(IJsEngine engine)
 		/// The first functioning JavaScript engine with the lowest priority will be used.
 		/// </summary>
 		/// <returns>Function to create JavaScript engine</returns>
-		private static Func<IJsEngine> GetFactory(IEnumerable<Registration> availableFactories)
+		private static Func<IJsEngine> GetFactory(IEnumerable<Registration> availableFactories, bool allowMsie)
 		{
 			var availableEngineFactories = availableFactories
 				.OrderBy(x => x.Priority)
@@ -208,8 +209,7 @@ private static Func<IJsEngine> GetFactory(IEnumerable<Registration> availableFac
 				try
 				{
 					engine = engineFactory();
-					// Perform a sanity test to ensure this engine is usable
-					if (engine.Evaluate<int>("1 + 1") == 2)
+					if (EngineIsUsable(engine, allowMsie))
 					{
 						// Success! Use this one.
 						return engineFactory;
@@ -246,6 +246,20 @@ private static Func<IJsEngine> GetFactory(IEnumerable<Registration> availableFac
 			throw new ReactEngineNotFoundException();
 		}
 
+		/// <summary>
+		/// Performs a sanity check to ensure the specified engine type is usable.
+		/// </summary>
+		/// <param name="engine">Engine to test</param>
+		/// <param name="allowMsie">Whether the MSIE engine can be used</param>
+		/// <returns></returns>
+		private static bool EngineIsUsable(IJsEngine engine, bool allowMsie)
+		{
+			// Perform a sanity test to ensure this engine is usable
+			var isUsable = engine.Evaluate<int>("1 + 1") == 2;
+			var isMsie = engine is MsieJsEngine;
+			return isUsable && (!isMsie || allowMsie);
+		}
+
 		/// <summary>
 		/// Clean up all engines
 		/// </summary>

src/React.Core/ReactSiteConfiguration.cs

@@ -35,6 +35,7 @@ public ReactSiteConfiguration()
 		{
 			UseHarmony = true;
 			ReuseJavaScriptEngines = true;
+			AllowMsieEngine = true;
 		}
 
 		/// <summary>
@@ -154,5 +155,20 @@ public IReactSiteConfiguration SetMaxEngines(int? maxEngines)
 			MaxEngines = maxEngines;
 			return this;
 		}
+
+		/// <summary>
+		/// Gets or sets whether the MSIE engine should be used if V8 is unavailable.
+		/// </summary>
+		public bool AllowMsieEngine { get; set; }
+
+		/// <summary>
+		/// Sets whether the MSIE engine should be used if V8 is unavailable.
+		/// </summary>
+		/// <returns></returns>
+		public IReactSiteConfiguration SetAllowMsieEngine(bool allowMsieEngine)
+		{
+			AllowMsieEngine = allowMsieEngine;
+			return this;
+		}
 	}
 }