refactor(ReactInstanceManager): Support awaitable ReactContext

Currently, the ReactInstanceManager kicks off the process to create the ReactContext in the background and its not awaitable. This ensures a single asynchronous thread is available from start to finish for ReactContext creation.

Fixes #1448

ReactWindows/ReactNative.Net46/ReactPage.cs

@@ -4,6 +4,7 @@
 using ReactNative.Modules.Core;
 using System;
 using System.Collections.Generic;
+using System.Threading;
 using System.Threading.Tasks;
 using System.Windows;
 using System.Windows.Controls;
@@ -181,7 +182,7 @@ protected virtual ReactRootView CreateRootView()
         /// </summary>
         /// <param name="sender"></param>
         /// <param name="e"></param>
-        private void OnAcceleratorKeyActivated(object sender, KeyEventArgs e)
+        private async void OnAcceleratorKeyActivated(object sender, KeyEventArgs e)
         {
             if (ReactInstanceManager.DevSupportManager.IsEnabled)
             {
@@ -196,7 +197,7 @@ private void OnAcceleratorKeyActivated(object sender, KeyEventArgs e)
                 // Ctrl+R
                 if (isCtrlKeyDown && e.Key == Key.R)
                 {
-                    ReactInstanceManager.DevSupportManager.HandleReloadJavaScript();
+                    await ReactInstanceManager.DevSupportManager.CreateReactContextFromPackagerAsync(CancellationToken.None);
                 }
             }
 

ReactWindows/ReactNative.Shared/Bridge/JavaScriptBundleLoader.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Threading;
 using System.Threading.Tasks;
 #if WINDOWS_UWP
 using Windows.Storage;
@@ -27,8 +28,9 @@ public abstract class JavaScriptBundleLoader
         /// Initializes the JavaScript bundle loader, typically making an
         /// asynchronous call to cache the bundle in memory.
         /// </summary>
+        /// <param name="token">A token to cancel the initialization.</param>
         /// <returns>A task to await initialization.</returns>
-        public abstract Task InitializeAsync();
+        public abstract Task InitializeAsync(CancellationToken token);
 
         /// <summary>
         /// Loads the bundle into a JavaScript executor.
@@ -89,13 +91,13 @@ public override string SourceUrl
             }
 
 #if WINDOWS_UWP
-            public override async Task InitializeAsync()
+            public override async Task InitializeAsync(CancellationToken token)
             {
-                var storageFile = await StorageFile.GetFileFromApplicationUriAsync(new Uri(SourceUrl)).AsTask().ConfigureAwait(false);
+                var storageFile = await StorageFile.GetFileFromApplicationUriAsync(new Uri(SourceUrl)).AsTask(token).ConfigureAwait(false);
                 _script = storageFile.Path;
             }
 #else
-            public override Task InitializeAsync()
+            public override Task InitializeAsync(CancellationToken token)
             {
                 var assembly = Assembly.GetAssembly(typeof(JavaScriptBundleLoader));
                 var assemblyName = assembly.GetName();
@@ -134,11 +136,11 @@ public CachedJavaScriptBundleLoader(string sourceUrl, string cachedFileLocation)
 
             public override string SourceUrl { get; }
 
-            public override async Task InitializeAsync()
+            public override async Task InitializeAsync(CancellationToken token)
             {
 #if WINDOWS_UWP
                 var localFolder = ApplicationData.Current.LocalFolder;
-                var storageFile = await localFolder.GetFileAsync(_cachedFileLocation).AsTask().ConfigureAwait(false);
+                var storageFile = await localFolder.GetFileAsync(_cachedFileLocation).AsTask(token).ConfigureAwait(false);
 #else
                 var localFolder = FileSystem.Current.LocalStorage;
                 var storageFile = await localFolder.GetFileAsync(_cachedFileLocation).ConfigureAwait(false);
@@ -170,7 +172,7 @@ public override string SourceUrl
                 get;
             }
 
-            public override Task InitializeAsync()
+            public override Task InitializeAsync(CancellationToken token)
             {
                 return Task.CompletedTask;
             }

ReactWindows/ReactNative.Shared/Bridge/ReactInstance.cs

@@ -7,6 +7,7 @@
 using System.Collections.Generic;
 using System.Globalization;
 using System.IO;
+using System.Threading;
 using System.Threading.Tasks;
 using static System.FormattableString;
 
@@ -81,9 +82,9 @@ public void Initialize()
             QueueConfiguration.NativeModulesQueue.Dispatch(_registry.NotifyReactInstanceInitialize);
         }
 
-        public async Task InitializeBridgeAsync()
+        public async Task InitializeBridgeAsync(CancellationToken token)
         {
-            await _bundleLoader.InitializeAsync().ConfigureAwait(false);
+            await _bundleLoader.InitializeAsync(token).ConfigureAwait(false);
 
             using (Tracer.Trace(Tracer.TRACE_TAG_REACT_BRIDGE, "initializeBridge").Start())
             {

ReactWindows/ReactNative.Shared/DevSupport/DevServerHelper.cs

@@ -1,4 +1,4 @@
-using ReactNative.Bridge;
+using ReactNative.Bridge;
 using System;
 using System.Globalization;
 using System.IO;
@@ -139,13 +139,14 @@ public async Task DownloadBundleFromUrlAsync(string jsModulePath, Stream outputS
         /// <summary>
         /// Checks if the packager is running.
         /// </summary>
+        /// <param name="token">A token to cancel the request.</param>
         /// <returns>A task to await the packager status.</returns>
-        public async Task<bool> IsPackagerRunningAsync()
+        public async Task<bool> IsPackagerRunningAsync(CancellationToken token)
         {
             var statusUrl = CreatePackagerStatusUrl(DebugServerHost);
             try
             {
-                using (var response = await _client.GetAsync(statusUrl).ConfigureAwait(false))
+                using (var response = await _client.GetAsync(statusUrl, token).ConfigureAwait(false))
                 {
                     if (!response.IsSuccessStatusCode)
                     {