Ensure ExecuteWithLargerStackIfRequired still uses JSON parsing logic if an exception is caught. References #104

Author: Daniel15

build.proj

@@ -11,7 +11,7 @@ of patent rights can be found in the PATENTS file in the same directory.
 	<PropertyGroup>
 		<Major>1</Major>
 		<Minor>4</Minor>
-		<Build>0</Build>
+		<Build>1</Build>
 		<Revision>0</Revision>
 		<DevNuGetServer>http://reactjs.net/packages/</DevNuGetServer>
 		<MSBuildCommunityTasksPath>$(MSBuildProjectDirectory)\tools\MSBuildTasks</MSBuildCommunityTasksPath>

src/React.Core/JavaScriptEngineUtils.cs

@@ -9,6 +9,8 @@
 
 using System;
 using JavaScriptEngineSwitcher.Core;
+using JavaScriptEngineSwitcher.Core.Helpers;
+using Newtonsoft.Json;
 using React.Exceptions;
 
 namespace React
@@ -63,5 +65,39 @@ Func<Exception, TException> exceptionFactory
 				throw new ReactException("Mathematics is broken. 1 + 1 = " + result);
 			}
 		}
+
+		/// <summary>
+		/// Calls a JavaScript function using the specified engine. If <typeparamref name="T"/> is
+		/// not a scalar type, the function is assumed to return a string of JSON that can be 
+		/// parsed as that type.
+		/// </summary>
+		/// <typeparam name="T">Type returned by function</typeparam>
+		/// <param name="engine">Engine to execute function with</param>
+		/// <param name="function">Name of the function to execute</param>
+		/// <param name="args">Arguments to pass to function</param>
+		/// <returns>Value returned by function</returns>
+		public static T CallFunctionReturningJson<T>(this IJsEngine engine, string function, params object[] args)
+		{
+			if (ValidationHelpers.IsSupportedType(typeof(T)))
+			{
+				// Type is supported directly (ie. a scalar type like string/int/bool)
+				// Just execute the function directly.
+				return engine.CallFunction<T>(function, args);
+			}
+			// The type is not a scalar type. Assume the function will return its result as
+			// JSON.
+			var resultJson = engine.CallFunction<string>(function, args);
+			try
+			{
+				return JsonConvert.DeserializeObject<T>(resultJson);
+			}
+			catch (JsonReaderException ex)
+			{
+				throw new ReactException(string.Format(
+					"{0} did not return valid JSON: {1}.\n\n{2}",
+					function, ex.Message, resultJson
+				));
+			}
+		}
 	}
 }

src/React.Core/ReactEnvironment.cs

@@ -231,26 +231,7 @@ public virtual T Execute<T>(string function, params object[] args)
 		{
 			try
 			{
-				if (ValidationHelpers.IsSupportedType(typeof (T)))
-				{
-					// Type is supported directly (ie. a scalar type like string/int/bool)
-					// Just execute the function directly.
-					return Engine.CallFunction<T>(function, args);
-				}
-				// The type is not a scalar type. Assume the function will return its result as
-				// JSON.
-				var resultJson = Engine.CallFunction<string>(function, args);
-				try
-				{
-					return JsonConvert.DeserializeObject<T>(resultJson);
-				}
-				catch (JsonReaderException ex)
-				{
-					throw new ReactException(string.Format(
-						"{0} did not return valid JSON: {1}.\n\n{2}",
-						function, ex.Message, resultJson
-					));
-				}
+				return Engine.CallFunctionReturningJson<T>(function, args);
 			}
 			catch (JsRuntimeException ex)
 			{
@@ -381,7 +362,7 @@ public virtual T ExecuteWithLargerStackIfRequired<T>(string function, params obj
 					var engine = _engineFactory.GetEngineForCurrentThread();
 					try
 					{
-						result = engine.CallFunction<T>(function, args);
+						result = engine.CallFunctionReturningJson<T>(function, args);
 					}
 					catch (Exception threadEx)
 					{

src/React.Tests/Core/JavaScriptEngineUtilsTests.cs

@@ -0,0 +1,50 @@
+/*
+ *  Copyright (c) 2015, Facebook, Inc.
+ *  All rights reserved.
+ *
+ *  This source code is licensed under the BSD-style license found in the
+ *  LICENSE file in the root directory of this source tree. An additional grant 
+ *  of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+using JavaScriptEngineSwitcher.Core;
+using Moq;
+using NUnit.Framework;
+using React.Exceptions;
+
+namespace React.Tests.Core
+{
+	[TestFixture]
+	public class JavaScriptEngineUtilsTests
+	{
+		[Test]
+		public void CallFunctionReturningJsonHandlesScalarReturnValue()
+		{
+			var engine = new Mock<IJsEngine>();
+			engine.Object.CallFunctionReturningJson<int>("hello");
+			engine.Verify(x => x.CallFunction<int>("hello"));
+		}
+
+		[Test]
+		public void CallFunctionReturningJsonHandlesJson()
+		{
+			var engine = new Mock<IJsEngine>();
+			engine.Setup(x => x.CallFunction<string>("hello")).Returns("{\"message\":\"Hello World\"}");
+			var result = engine.Object.CallFunctionReturningJson<Example>("hello");
+			Assert.AreEqual("Hello World", result.Message);
+		}
+
+		[Test]
+		public void CallFunctionReturningJsonThrowsOnInvalidJson()
+		{
+			var engine = new Mock<IJsEngine>();
+			engine.Setup(x => x.CallFunction<string>("hello")).Returns("lol wut this is not json '\"");
+			Assert.Throws<ReactException>(() => engine.Object.CallFunctionReturningJson<Example>("hello"));
+		}
+
+        private class Example
+		{
+			public string Message { get; set; }
+		}
+	}
+}

src/React.Tests/React.Tests.csproj

@@ -97,6 +97,7 @@
     </Compile>
     <Compile Include="Core\FileCacheHashTests.cs" />
     <Compile Include="Core\JavaScriptEngineFactoryTest.cs" />
+    <Compile Include="Core\JavaScriptEngineUtilsTests.cs" />
     <Compile Include="Core\JsxTransformerTests.cs" />
     <Compile Include="Core\ReactComponentTest.cs" />
     <Compile Include="Mvc\HtmlHelperExtensionsTests.cs" />