Add ability to provide React version rather than always loading the built-in version. Closes reactjs#113

Author: Daniel15

src/React.Core/IReactSiteConfiguration.cs

@@ -130,5 +130,17 @@ public interface IReactSiteConfiguration
 		/// </summary>
 		/// <returns></returns>
 		IReactSiteConfiguration SetAllowMsieEngine(bool allowMsieEngine);
+
+		/// <summary>
+		/// Gets or sets whether the built-in version of React is loaded. If <c>false</c>, you must
+		/// provide your own version of React.
+		/// </summary>
+		bool LoadReact { get; set; }
+		/// <summary>
+		/// Sets whether the built-in version of React is loaded. If <c>false</c>, you must 
+		/// provide your own version of React.
+		/// </summary>
+		/// <returns>The configuration, for chaining</returns>
+		IReactSiteConfiguration SetLoadReact(bool loadReact);
 	}
 }

src/React.Core/JavaScriptEngineFactory.cs

@@ -135,12 +135,29 @@ protected virtual void InitialiseEngine(IJsEngine engine)
 		{
 			var thisAssembly = typeof(ReactEnvironment).Assembly;
 			engine.ExecuteResource("React.Resources.shims.js", thisAssembly);
-			engine.ExecuteResource("React.Resources.react-with-addons.js", thisAssembly);
-			engine.Execute("var React = global.React");
-			engine.ExecuteResource("React.Resources.JSXTransformer.js", thisAssembly);
+			if (_config.LoadReact)
+			{
+				engine.ExecuteResource("React.Resources.react-with-addons.js", thisAssembly);
+				engine.Execute("React = global.React");
+				engine.ExecuteResource("React.Resources.JSXTransformer.js", thisAssembly);
+			}
 
-			// Only scripts that don't need JSX transformation can run immediately here
-			// JSX files are loaded in ReactEnvironment.
+			LoadUserScripts(engine);
+			if (!_config.LoadReact)
+			{
+				// We expect to user to have loaded their own versino of React in the scripts that
+				// were loaded above, let's ensure that's the case. 
+				EnsureReactLoaded(engine);
+			}
+		}
+
+		/// <summary>
+		/// Loads any user-provided scripts. Only scripts that don't need JSX transformation can 
+		/// run immediately here. JSX files are loaded in ReactEnvironment.
+		/// </summary>
+		/// <param name="engine">Engine to load scripts into</param>
+		private void LoadUserScripts(IJsEngine engine)
+		{
 			foreach (var file in _config.ScriptsWithoutTransform)
 			{
 				try
@@ -161,6 +178,23 @@ protected virtual void InitialiseEngine(IJsEngine engine)
 			}
 		}
 
+		/// <summary>
+		/// Ensures that React has been correctly loaded into the specified engine.
+		/// </summary>
+		/// <param name="engine">Engine to check</param>
+		private static void EnsureReactLoaded(IJsEngine engine)
+		{
+			var result = engine.CallFunction<bool>("ReactNET_initReact");
+			if (!result)
+			{
+				throw new ReactNotInitialisedException(
+					"React has not been loaded correctly. Please expose your version of React as a global " +
+					"variable named 'React', or enable the 'LoadReact' configuration option to " +
+					"use the built-in version of React."
+				);
+			}
+		}
+
 		/// <summary>
 		/// Gets the JavaScript engine for the current thread. It is recommended to use 
 		/// <see cref="GetEngine"/> instead, which will pool/reuse engines.

src/React.Core/ReactSiteConfiguration.cs

@@ -36,6 +36,7 @@ public ReactSiteConfiguration()
 			UseHarmony = true;
 			ReuseJavaScriptEngines = true;
 			AllowMsieEngine = true;
+			LoadReact = true;
 		}
 
 		/// <summary>
@@ -203,5 +204,22 @@ public IReactSiteConfiguration SetAllowMsieEngine(bool allowMsieEngine)
 			AllowMsieEngine = allowMsieEngine;
 			return this;
 		}
+
+		/// <summary>
+		/// Gets or sets whether the built-in version of React is loaded. If <c>false</c>, you must
+		/// provide your own version of React.
+		/// </summary>
+		public bool LoadReact { get; set; }
+
+		/// <summary>
+		/// Sets whether the built-in version of React is loaded. If <c>false</c>, you must 
+		/// provide your own version of React.
+		/// </summary>
+		/// <returns>The configuration, for chaining</returns>
+		public IReactSiteConfiguration SetLoadReact(bool loadReact)
+		{
+			LoadReact = loadReact;
+			return this;
+		}
 	}
 }

src/React.Core/Resources/shims.js

@@ -8,6 +8,7 @@
  */
 
 var global = global || {};
+var React;
 
 // Basic console shim. Caches all calls to console methods.
 function MockConsole() {
@@ -40,6 +41,29 @@ if (!Object.freeze) {
 	Object.freeze = function() { };
 }
 
+/**
+ * Finds a user-supplied version of React and ensures it's exposed globally.
+ *
+ * @return {bool}
+ */
+function ReactNET_initReact() {
+	if (typeof React !== 'undefined') {
+		// React is already a global, woohoo
+		return true;
+	}
+	if (global.React) {
+		React = global.React;
+		return true;
+	}
+	if (typeof require === 'function') {
+		// CommonJS-like environment (eg. Browserify)
+		React = require('react');
+		return true;
+	}
+	// :'(
+	return false;
+}
+
 function ReactNET_transform(input, harmony, stripTypes) {
 	try {
 		return global.JSXTransformer.transform(input, {

src/React.Sample.Webpack/webpack.config.js

@@ -22,7 +22,10 @@ module.exports = {
   module: {
     loaders: [
       // Transform JSX in .jsx files
-      { test: /\.jsx$/, loader: 'jsx-loader?harmony' }
+      { test: /\.jsx$/, loader: 'jsx-loader?harmony' },
+	  // Uncomment this if you want to use your own version of React instead of the version 
+	  // bundled with ReactJS.NET.
+	  //{ test: require.resolve('react'), loader: 'expose?React' }
     ],
   },
   resolve: {
@@ -31,6 +34,7 @@ module.exports = {
   },
   externals: {
     // Use external version of React (from CDN for client-side, or bundled with ReactJS.NET for server-side)
+	// Comment this out if you want to load your own version of React
     react: 'React'
   }
 };