Add new Microsoft.AspNetCore.SpaServices.Extensions package to host new runtime functionality needed for updated templates until 2.1 ships

JavaScriptServices.sln

@@ -1,7 +1,7 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio 15
-VisualStudioVersion = 15.0.26730.0
+VisualStudioVersion = 15.0.26730.16
 MinimumVisualStudioVersion = 15.0.26730.03
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "src", "src", "{27304DDE-AFB2-4F8B-B765-E3E2F11E886C}"
 	ProjectSection(SolutionItems) = preProject
@@ -37,6 +37,8 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution
 		Directory.Build.targets = Directory.Build.targets
 	EndProjectSection
 EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.AspNetCore.SpaServices.Extensions", "src\Microsoft.AspNetCore.SpaServices.Extensions\Microsoft.AspNetCore.SpaServices.Extensions.csproj", "{D40BD1C4-6A6F-4213-8535-1057F3EB3400}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -67,6 +69,10 @@ Global
 		{93EFCC5F-C6EE-4623-894F-A42B22C0B6FE}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{93EFCC5F-C6EE-4623-894F-A42B22C0B6FE}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{93EFCC5F-C6EE-4623-894F-A42B22C0B6FE}.Release|Any CPU.Build.0 = Release|Any CPU
+		{D40BD1C4-6A6F-4213-8535-1057F3EB3400}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{D40BD1C4-6A6F-4213-8535-1057F3EB3400}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{D40BD1C4-6A6F-4213-8535-1057F3EB3400}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{D40BD1C4-6A6F-4213-8535-1057F3EB3400}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -79,6 +85,7 @@ Global
 		{1931B19A-EC42-4D56-B2D0-FB06D17244DA} = {E6A161EA-646C-4033-9090-95BE809AB8D9}
 		{DE479DC3-1461-4EAD-A188-4AF7AA4AE344} = {E6A161EA-646C-4033-9090-95BE809AB8D9}
 		{93EFCC5F-C6EE-4623-894F-A42B22C0B6FE} = {E6A161EA-646C-4033-9090-95BE809AB8D9}
+		{D40BD1C4-6A6F-4213-8535-1057F3EB3400} = {27304DDE-AFB2-4F8B-B765-E3E2F11E886C}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {DDF59B0D-2DEC-45D6-8667-DCB767487101}

build/dependencies.props

@@ -13,6 +13,7 @@
     <MicrosoftAspNetCoreServerIISIntegrationPackageVersion>2.1.0-preview1-27478</MicrosoftAspNetCoreServerIISIntegrationPackageVersion>
     <MicrosoftAspNetCoreServerKestrelPackageVersion>2.1.0-preview1-27478</MicrosoftAspNetCoreServerKestrelPackageVersion>
     <MicrosoftAspNetCoreStaticFilesPackageVersion>2.1.0-preview1-27478</MicrosoftAspNetCoreStaticFilesPackageVersion>
+    <MicrosoftAspNetCoreWebSocketsPackageVersion>2.1.0-preview1-27478</MicrosoftAspNetCoreWebSocketsPackageVersion>
     <MicrosoftExtensionsDependencyInjectionPackageVersion>2.1.0-preview1-27478</MicrosoftExtensionsDependencyInjectionPackageVersion>
     <MicrosoftExtensionsLoggingConsolePackageVersion>2.1.0-preview1-27478</MicrosoftExtensionsLoggingConsolePackageVersion>
     <MicrosoftExtensionsLoggingDebugPackageVersion>2.1.0-preview1-27478</MicrosoftExtensionsLoggingDebugPackageVersion>

src/Microsoft.AspNetCore.SpaServices.Extensions/AngularCli/AngularCliBuilder.cs

@@ -0,0 +1,73 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.NodeServices.Npm;
+using Microsoft.AspNetCore.NodeServices.Util;
+using Microsoft.AspNetCore.SpaServices.Prerendering;
+using System;
+using System.IO;
+using System.Text.RegularExpressions;
+using System.Threading.Tasks;
+
+namespace Microsoft.AspNetCore.SpaServices.AngularCli
+{
+    /// <summary>
+    /// Provides an implementation of <see cref="ISpaPrerendererBuilder"/> that can build
+    /// an Angular application by invoking the Angular CLI.
+    /// </summary>
+    public class AngularCliBuilder : ISpaPrerendererBuilder
+    {
+        private static TimeSpan RegexMatchTimeout = TimeSpan.FromSeconds(5); // This is a development-time only feature, so a very long timeout is fine
+        private static TimeSpan BuildTimeout = TimeSpan.FromSeconds(50); // Note that the HTTP request itself by default times out after 60s, so you only get useful error information if this is shorter
+
+        private readonly string _npmScriptName;
+
+        /// <summary>
+        /// Constructs an instance of <see cref="AngularCliBuilder"/>.
+        /// </summary>
+        /// <param name="npmScript">The name of the script in your package.json file that builds the server-side bundle for your Angular application.</param>
+        public AngularCliBuilder(string npmScript)
+        {
+            if (string.IsNullOrEmpty(npmScript))
+            {
+                throw new ArgumentException("Cannot be null or empty.", nameof(npmScript));
+            }
+
+            _npmScriptName = npmScript;
+        }
+
+        /// <inheritdoc />
+        public Task Build(ISpaBuilder spaBuilder)
+        {
+            var sourcePath = spaBuilder.Options.SourcePath;
+            if (string.IsNullOrEmpty(sourcePath))
+            {
+                throw new InvalidOperationException($"To use {nameof(AngularCliBuilder)}, you must supply a non-empty value for the {nameof(SpaOptions.SourcePath)} property of {nameof(SpaOptions)} when calling {nameof(SpaApplicationBuilderExtensions.UseSpa)}.");
+            }
+
+            var logger = AngularCliMiddleware.GetOrCreateLogger(spaBuilder.ApplicationBuilder);
+            var npmScriptRunner = new NpmScriptRunner(
+                sourcePath,
+                _npmScriptName,
+                "--watch");
+            npmScriptRunner.AttachToLogger(logger);
+
+            using (var stdErrReader = new EventedStreamStringReader(npmScriptRunner.StdErr))
+            {
+                try
+                {
+                    return npmScriptRunner.StdOut.WaitForMatch(
+                        new Regex("chunk", RegexOptions.None, RegexMatchTimeout),
+                        BuildTimeout);
+                }
+                catch (EndOfStreamException ex)
+                {
+                    throw new InvalidOperationException(
+                        $"The NPM script '{_npmScriptName}' exited without indicating success. " +
+                        $"Error output was: {stdErrReader.ReadAsString()}", ex);
+                }
+            }
+        }
+    }
+}

src/Microsoft.AspNetCore.SpaServices.Extensions/AngularCli/AngularCliMiddleware.cs

@@ -0,0 +1,131 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNetCore.Builder;
+using System;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.NodeServices.Npm;
+using System.Text.RegularExpressions;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging.Console;
+using System.Net.Sockets;
+using System.Net;
+using System.IO;
+using Microsoft.AspNetCore.NodeServices.Util;
+
+namespace Microsoft.AspNetCore.SpaServices.AngularCli
+{
+    internal static class AngularCliMiddleware
+    {
+        private const string LogCategoryName = "Microsoft.AspNetCore.SpaServices";
+        private static TimeSpan RegexMatchTimeout = TimeSpan.FromSeconds(5); // This is a development-time only feature, so a very long timeout is fine
+        private static TimeSpan StartupTimeout = TimeSpan.FromSeconds(50); // Note that the HTTP request itself by default times out after 60s, so you only get useful error information if this is shorter
+
+        public static void Attach(
+            ISpaBuilder spaBuilder,
+            string npmScriptName)
+        {
+            var sourcePath = spaBuilder.Options.SourcePath;
+            if (string.IsNullOrEmpty(sourcePath))
+            {
+                throw new ArgumentException("Cannot be null or empty", nameof(sourcePath));
+            }
+
+            if (string.IsNullOrEmpty(npmScriptName))
+            {
+                throw new ArgumentException("Cannot be null or empty", nameof(npmScriptName));
+            }
+
+            // Start Angular CLI and attach to middleware pipeline
+            var appBuilder = spaBuilder.ApplicationBuilder;
+            var logger = GetOrCreateLogger(appBuilder);
+            var angularCliServerInfoTask = StartAngularCliServerAsync(sourcePath, npmScriptName, logger);
+
+            // Everything we proxy is hardcoded to target http://localhost because:
+            // - the requests are always from the local machine (we're not accepting remote
+            //   requests that go directly to the Angular CLI middleware server)
+            // - given that, there's no reason to use https, and we couldn't even if we
+            //   wanted to, because in general the Angular CLI server has no certificate
+            var targetUriTask = angularCliServerInfoTask.ContinueWith(
+                task => new UriBuilder("http", "localhost", task.Result.Port).Uri);
+
+            SpaProxyingExtensions.UseProxyToSpaDevelopmentServer(spaBuilder, targetUriTask);
+        }
+
+        internal static ILogger GetOrCreateLogger(IApplicationBuilder appBuilder)
+        {
+            // If the DI system gives us a logger, use it. Otherwise, set up a default one.
+            var loggerFactory = appBuilder.ApplicationServices.GetService<ILoggerFactory>();
+            var logger = loggerFactory != null
+                ? loggerFactory.CreateLogger(LogCategoryName)
+                : new ConsoleLogger(LogCategoryName, null, false);
+            return logger;
+        }
+
+        private static async Task<AngularCliServerInfo> StartAngularCliServerAsync(
+            string sourcePath, string npmScriptName, ILogger logger)
+        {
+            var portNumber = FindAvailablePort();
+            logger.LogInformation($"Starting @angular/cli on port {portNumber}...");
+
+            var npmScriptRunner = new NpmScriptRunner(
+                sourcePath, npmScriptName, $"--port {portNumber}");
+            npmScriptRunner.AttachToLogger(logger);
+
+            Match openBrowserLine;
+            using (var stdErrReader = new EventedStreamStringReader(npmScriptRunner.StdErr))
+            {
+                try
+                {
+                    openBrowserLine = await npmScriptRunner.StdOut.WaitForMatch(
+                        new Regex("open your browser on (http\\S+)", RegexOptions.None, RegexMatchTimeout),
+                        StartupTimeout);
+                }
+                catch (EndOfStreamException ex)
+                {
+                    throw new InvalidOperationException(
+                        $"The NPM script '{npmScriptName}' exited without indicating that the " +
+                        $"Angular CLI was listening for requests. The error output was: " +
+                        $"{stdErrReader.ReadAsString()}", ex);
+                }
+                catch (TaskCanceledException ex)
+                {
+                    throw new InvalidOperationException(
+                        $"The Angular CLI process did not start listening for requests " +
+                        $"within the timeout period of {StartupTimeout.Seconds} seconds. " +
+                        $"Check the log output for error information.", ex);
+                }
+            }
+
+            var uri = new Uri(openBrowserLine.Groups[1].Value);
+            var serverInfo = new AngularCliServerInfo { Port = uri.Port };
+
+            // Even after the Angular CLI claims to be listening for requests, there's a short
+            // period where it will give an error if you make a request too quickly. Give it
+            // a moment to finish starting up.
+            await Task.Delay(500);
+
+            return serverInfo;
+        }
+
+        private static int FindAvailablePort()
+        {
+            var listener = new TcpListener(IPAddress.Loopback, 0);
+            listener.Start();
+            try
+            {
+                return ((IPEndPoint)listener.LocalEndpoint).Port;
+            }
+            finally
+            {
+                listener.Stop();
+            }
+        }
+
+        class AngularCliServerInfo
+        {
+            public int Port { get; set; }
+        }
+    }
+}

src/Microsoft.AspNetCore.SpaServices.Extensions/AngularCli/AngularCliMiddlewareExtensions.cs

@@ -0,0 +1,43 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNetCore.Builder;
+using System;
+
+namespace Microsoft.AspNetCore.SpaServices.AngularCli
+{
+    /// <summary>
+    /// Extension methods for enabling Angular CLI middleware support.
+    /// </summary>
+    public static class AngularCliMiddlewareExtensions
+    {
+        /// <summary>
+        /// Handles requests by passing them through to an instance of the Angular CLI server.
+        /// This means you can always serve up-to-date CLI-built resources without having
+        /// to run the Angular CLI server manually.
+        ///
+        /// This feature should only be used in development. For production deployments, be
+        /// sure not to enable the Angular CLI server.
+        /// </summary>
+        /// <param name="spaBuilder">The <see cref="ISpaBuilder"/>.</param>
+        /// <param name="npmScript">The name of the script in your package.json file that launches the Angular CLI process.</param>
+        public static void UseAngularCliServer(
+            this ISpaBuilder spaBuilder,
+            string npmScript)
+        {
+            if (spaBuilder == null)
+            {
+                throw new ArgumentNullException(nameof(spaBuilder));
+            }
+
+            var spaOptions = spaBuilder.Options;
+
+            if (string.IsNullOrEmpty(spaOptions.SourcePath))
+            {
+                throw new InvalidOperationException($"To use {nameof(UseAngularCliServer)}, you must supply a non-empty value for the {nameof(SpaOptions.SourcePath)} property of {nameof(SpaOptions)} when calling {nameof(SpaApplicationBuilderExtensions.UseSpa)}.");
+            }
+
+            AngularCliMiddleware.Attach(spaBuilder, npmScript);
+        }
+    }
+}

src/Microsoft.AspNetCore.SpaServices.Extensions/DefaultSpaBuilder.cs

@@ -0,0 +1,24 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNetCore.Builder;
+using System;
+
+namespace Microsoft.AspNetCore.SpaServices
+{
+    internal class DefaultSpaBuilder : ISpaBuilder
+    {
+        public IApplicationBuilder ApplicationBuilder { get; }
+
+        public SpaOptions Options { get; }
+
+        public DefaultSpaBuilder(IApplicationBuilder applicationBuilder, SpaOptions options)
+        {
+            ApplicationBuilder = applicationBuilder 
+                ?? throw new ArgumentNullException(nameof(applicationBuilder));
+
+            Options = options
+                ?? throw new ArgumentNullException(nameof(options));
+        }
+    }
+}

src/Microsoft.AspNetCore.SpaServices.Extensions/ISpaBuilder.cs

@@ -0,0 +1,25 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNetCore.Builder;
+
+namespace Microsoft.AspNetCore.SpaServices
+{
+    /// <summary>
+    /// Defines a class that provides mechanisms for configuring the hosting
+    /// of a Single Page Application (SPA) and attaching middleware.
+    /// </summary>
+    public interface ISpaBuilder
+    {
+        /// <summary>
+        /// The <see cref="IApplicationBuilder"/> representing the middleware pipeline
+        /// in which the SPA is being hosted.
+        /// </summary>
+        IApplicationBuilder ApplicationBuilder { get; }
+
+        /// <summary>
+        /// Describes configuration options for hosting a SPA.
+        /// </summary>
+        SpaOptions Options { get; }
+    }
+}

src/Microsoft.AspNetCore.SpaServices.Extensions/Microsoft.AspNetCore.SpaServices.Extensions.csproj

@@ -0,0 +1,17 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <Description>Helpers for building single-page applications on ASP.NET MVC Core.</Description>
+    <TargetFramework>netstandard2.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Microsoft.AspNetCore.SpaServices\Microsoft.AspNetCore.SpaServices.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.AspNetCore.StaticFiles" Version="$(MicrosoftAspNetCoreStaticFilesPackageVersion)" />
+    <PackageReference Include="Microsoft.AspNetCore.WebSockets" Version="$(MicrosoftAspNetCoreWebSocketsPackageVersion)" />
+  </ItemGroup>
+
+</Project>

src/Microsoft.AspNetCore.SpaServices.Extensions/Npm/EventedStreamReader.cs

@@ -0,0 +1,134 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.IO;
+using System.Text;
+using System.Text.RegularExpressions;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Microsoft.AspNetCore.NodeServices.Util
+{
+    /// <summary>
+    /// Wraps a <see cref="StreamReader"/> to expose an evented API, issuing notifications
+    /// when the stream emits partial lines, completed lines, or finally closes.
+    /// </summary>
+    internal class EventedStreamReader
+    {
+        public delegate void OnReceivedChunkHandler(ArraySegment<char> chunk);
+        public delegate void OnReceivedLineHandler(string line);
+        public delegate void OnStreamClosedHandler();
+
+        public event OnReceivedChunkHandler OnReceivedChunk;
+        public event OnReceivedLineHandler OnReceivedLine;
+        public event OnStreamClosedHandler OnStreamClosed;
+
+        private readonly StreamReader _streamReader;
+        private readonly StringBuilder _linesBuffer;
+
+        public EventedStreamReader(StreamReader streamReader)
+        {
+            _streamReader = streamReader ?? throw new ArgumentNullException(nameof(streamReader));
+            _linesBuffer = new StringBuilder();
+            Task.Factory.StartNew(Run);
+        }
+
+        public Task<Match> WaitForMatch(Regex regex, TimeSpan timeout = default)
+        {
+            var tcs = new TaskCompletionSource<Match>();
+            var completionLock = new object();
+
+            OnReceivedLineHandler onReceivedLineHandler = null;
+            OnStreamClosedHandler onStreamClosedHandler = null;
+
+            void ResolveIfStillPending(Action applyResolution)
+            {
+                lock (completionLock)
+                {
+                    if (!tcs.Task.IsCompleted)
+                    {
+                        OnReceivedLine -= onReceivedLineHandler;
+                        OnStreamClosed -= onStreamClosedHandler;
+                        applyResolution();
+                    }
+                }
+            }
+
+            onReceivedLineHandler = line =>
+            {
+                var match = regex.Match(line);
+                if (match.Success)
+                {
+                    ResolveIfStillPending(() => tcs.SetResult(match));
+                }
+            };
+
+            onStreamClosedHandler = () =>
+            {
+                ResolveIfStillPending(() => tcs.SetException(new EndOfStreamException()));
+            };
+
+            OnReceivedLine += onReceivedLineHandler;
+            OnStreamClosed += onStreamClosedHandler;
+
+            if (timeout != default)
+            {
+                var timeoutToken = new CancellationTokenSource(timeout);
+                timeoutToken.Token.Register(() =>
+                {
+                    ResolveIfStillPending(() => tcs.SetCanceled());
+                });
+            }
+
+            return tcs.Task;
+        }
+
+        private async Task Run()
+        {
+            var buf = new char[8 * 1024];
+            while (true)
+            {
+                var chunkLength = await _streamReader.ReadAsync(buf, 0, buf.Length);
+                if (chunkLength == 0)
+                {
+                    OnClosed();
+                    break;
+                }
+
+                OnChunk(new ArraySegment<char>(buf, 0, chunkLength));
+
+                var lineBreakPos = Array.IndexOf(buf, '\n', 0, chunkLength);
+                if (lineBreakPos < 0)
+                {
+                    _linesBuffer.Append(buf, 0, chunkLength);
+                }
+                else
+                {
+                    _linesBuffer.Append(buf, 0, lineBreakPos + 1);
+                    OnCompleteLine(_linesBuffer.ToString());
+                    _linesBuffer.Clear();
+                    _linesBuffer.Append(buf, lineBreakPos + 1, chunkLength - (lineBreakPos + 1));
+                }
+            }
+        }
+
+        private void OnChunk(ArraySegment<char> chunk)
+        {
+            var dlg = OnReceivedChunk;
+            dlg?.Invoke(chunk);
+        }
+
+        private void OnCompleteLine(string line)
+        {
+            var dlg = OnReceivedLine;
+            dlg?.Invoke(line);
+        }
+
+        private void OnClosed()
+        {
+            var dlg = OnStreamClosed;
+            dlg?.Invoke();
+        }
+    }
+}

src/Microsoft.AspNetCore.SpaServices.Extensions/Npm/EventedStreamStringReader.cs

@@ -0,0 +1,39 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Text;
+
+namespace Microsoft.AspNetCore.NodeServices.Util
+{
+    /// <summary>
+    /// Captures the completed-line notifications from a <see cref="EventedStreamReader"/>,
+    /// combining the data into a single <see cref="string"/>.
+    /// </summary>
+    internal class EventedStreamStringReader : IDisposable
+    {
+        private EventedStreamReader _eventedStreamReader;
+        private bool _isDisposed;
+        private StringBuilder _stringBuilder = new StringBuilder();
+
+        public EventedStreamStringReader(EventedStreamReader eventedStreamReader)
+        {
+            _eventedStreamReader = eventedStreamReader
+                ?? throw new ArgumentNullException(nameof(eventedStreamReader));
+            _eventedStreamReader.OnReceivedLine += OnReceivedLine;
+        }
+
+        public string ReadAsString() => _stringBuilder.ToString();
+
+        private void OnReceivedLine(string line) => _stringBuilder.AppendLine(line);
+
+        public void Dispose()
+        {
+            if (!_isDisposed)
+            {
+                _eventedStreamReader.OnReceivedLine -= OnReceivedLine;
+                _isDisposed = true;
+            }
+        }
+    }
+}

src/Microsoft.AspNetCore.SpaServices.Extensions/Npm/NpmScriptRunner.cs

@@ -0,0 +1,121 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.Extensions.Logging;
+using Microsoft.AspNetCore.NodeServices.Util;
+using System;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Text.RegularExpressions;
+
+// This is under the NodeServices namespace because post 2.1 it will be moved to that package
+namespace Microsoft.AspNetCore.NodeServices.Npm
+{
+    /// <summary>
+    /// Executes the <c>script</c> entries defined in a <c>package.json</c> file,
+    /// capturing any output written to stdio.
+    /// </summary>
+    internal class NpmScriptRunner
+    {
+        public EventedStreamReader StdOut { get; }
+        public EventedStreamReader StdErr { get; }
+
+        private static Regex AnsiColorRegex = new Regex("\x001b\\[[0-9;]*m", RegexOptions.None, TimeSpan.FromSeconds(1));
+
+        public NpmScriptRunner(string workingDirectory, string scriptName, string arguments)
+        {
+            if (string.IsNullOrEmpty(workingDirectory))
+            {
+                throw new ArgumentException("Cannot be null or empty.", nameof(workingDirectory));
+            }
+
+            if (string.IsNullOrEmpty(scriptName))
+            {
+                throw new ArgumentException("Cannot be null or empty.", nameof(scriptName));
+            }
+
+            var npmExe = "npm";
+            var completeArguments = $"run {scriptName} -- {arguments ?? string.Empty}";
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            {
+                // On Windows, the NPM executable is a .cmd file, so it can't be executed
+                // directly (except with UseShellExecute=true, but that's no good, because
+                // it prevents capturing stdio). So we need to invoke it via "cmd /c".
+                npmExe = "cmd";
+                completeArguments = $"/c npm {completeArguments}";
+            }
+
+            var process = LaunchNodeProcess(new ProcessStartInfo(npmExe)
+            {
+                Arguments = completeArguments,
+                UseShellExecute = false,
+                RedirectStandardInput = true,
+                RedirectStandardOutput = true,
+                RedirectStandardError = true,
+                WorkingDirectory = workingDirectory
+            });
+
+            StdOut = new EventedStreamReader(process.StandardOutput);
+            StdErr = new EventedStreamReader(process.StandardError);
+        }
+
+        public void AttachToLogger(ILogger logger)
+        {
+            // When the NPM task emits complete lines, pass them through to the real logger
+            StdOut.OnReceivedLine += line =>
+            {
+                if (!string.IsNullOrWhiteSpace(line))
+                {
+                    // NPM tasks commonly emit ANSI colors, but it wouldn't make sense to forward
+                    // those to loggers (because a logger isn't necessarily any kind of terminal)
+                    logger.LogInformation(StripAnsiColors(line));
+                }
+            };
+
+            StdErr.OnReceivedLine += line =>
+            {
+                if (!string.IsNullOrWhiteSpace(line))
+                {
+                    logger.LogError(StripAnsiColors(line));
+                }
+            };
+
+            // But when it emits incomplete lines, assume this is progress information and
+            // hence just pass it through to StdOut regardless of logger config.
+            StdErr.OnReceivedChunk += chunk =>
+            {
+                var containsNewline = Array.IndexOf(
+                    chunk.Array, '\n', chunk.Offset, chunk.Count) >= 0;
+                if (!containsNewline)
+                {
+                    Console.Write(chunk.Array, chunk.Offset, chunk.Count);
+                }
+            };
+        }
+
+        private static string StripAnsiColors(string line)
+            => AnsiColorRegex.Replace(line, string.Empty);
+
+        private static Process LaunchNodeProcess(ProcessStartInfo startInfo)
+        {
+            try
+            {
+                var process = Process.Start(startInfo);
+
+                // See equivalent comment in OutOfProcessNodeInstance.cs for why
+                process.EnableRaisingEvents = true;
+
+                return process;
+            }
+            catch (Exception ex)
+            {
+                var message = $"Failed to start 'npm'. To resolve this:.\n\n"
+                            + "[1] Ensure that 'npm' is installed and can be found in one of the PATH directories.\n"
+                            + $"    Current PATH enviroment variable is: { Environment.GetEnvironmentVariable("PATH") }\n"
+                            + "    Make sure the executable is in one of those directories, or update your PATH.\n\n"
+                            + "[2] See the InnerException for further details of the cause.";
+                throw new InvalidOperationException(message, ex);
+            }
+        }
+    }
+}

src/Microsoft.AspNetCore.SpaServices.Extensions/Prerendering/ISpaPrerendererBuilder.cs

@@ -0,0 +1,25 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNetCore.Builder;
+using System.Threading.Tasks;
+
+namespace Microsoft.AspNetCore.SpaServices.Prerendering
+{
+    /// <summary>
+    /// Represents the ability to build a Single Page Application (SPA) on demand
+    /// so that it can be prerendered. This is only intended to be used at development
+    /// time. In production, a SPA should already have been built during publishing.
+    /// </summary>
+    public interface ISpaPrerendererBuilder
+    {
+        /// <summary>
+        /// Builds the Single Page Application so that a JavaScript entrypoint file
+        /// exists on disk. Prerendering middleware can then execute that file in
+        /// a Node environment.
+        /// </summary>
+        /// <param name="spaBuilder">The <see cref="ISpaBuilder"/>.</param>
+        /// <returns>A <see cref="Task"/> representing completion of the build process.</returns>
+        Task Build(ISpaBuilder spaBuilder);
+    }
+}

src/Microsoft.AspNetCore.SpaServices.Extensions/Prerendering/SpaPrerenderingExtensions.cs

@@ -0,0 +1,219 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Http.Features;
+using Microsoft.AspNetCore.NodeServices;
+using Microsoft.AspNetCore.SpaServices;
+using Microsoft.AspNetCore.SpaServices.Prerendering;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Net.Http.Headers;
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Microsoft.AspNetCore.Builder
+{
+    /// <summary>
+    /// Extension methods for configuring prerendering of a Single Page Application.
+    /// </summary>
+    public static class SpaPrerenderingExtensions
+    {
+        /// <summary>
+        /// Enables server-side prerendering middleware for a Single Page Application.
+        /// </summary>
+        /// <param name="spaBuilder">The <see cref="ISpaBuilder"/>.</param>
+        /// <param name="configuration">Supplies configuration for the prerendering middleware.</param>
+        public static void UseSpaPrerendering(
+            this ISpaBuilder spaBuilder,
+            Action<SpaPrerenderingOptions> configuration)
+        {
+            if (spaBuilder == null)
+            {
+                throw new ArgumentNullException(nameof(spaBuilder));
+            }
+
+            if (configuration == null)
+            {
+                throw new ArgumentNullException(nameof(configuration));
+            }
+
+            var options = new SpaPrerenderingOptions();
+            configuration.Invoke(options);
+
+            var capturedBootModulePath = options.BootModulePath;
+            if (string.IsNullOrEmpty(capturedBootModulePath))
+            {
+                throw new InvalidOperationException($"To use {nameof(UseSpaPrerendering)}, you " +
+                    $"must set a nonempty value on the ${nameof(SpaPrerenderingOptions.BootModulePath)} " +
+                    $"property on the ${nameof(SpaPrerenderingOptions)}.");
+            }
+
+            // If we're building on demand, start that process in the background now
+            var buildOnDemandTask = options.BuildOnDemand?.Build(spaBuilder);
+
+            // Get all the necessary context info that will be used for each prerendering call
+            var applicationBuilder = spaBuilder.ApplicationBuilder;
+            var serviceProvider = applicationBuilder.ApplicationServices;
+            var nodeServices = GetNodeServices(serviceProvider);
+            var applicationStoppingToken = serviceProvider.GetRequiredService<IApplicationLifetime>()
+                .ApplicationStopping;
+            var applicationBasePath = serviceProvider.GetRequiredService<IHostingEnvironment>()
+                .ContentRootPath;
+            var moduleExport = new JavaScriptModuleExport(capturedBootModulePath);
+            var excludePathStrings = (options.ExcludeUrls ?? Array.Empty<string>())
+                .Select(url => new PathString(url))
+                .ToArray();
+
+            applicationBuilder.Use(async (context, next) =>
+            {
+                // If this URL is excluded, skip prerendering.
+                // This is typically used to ensure that static client-side resources
+                // (e.g., /dist/*.css) are served normally or through SPA development
+                // middleware, and don't return the prerendered index.html page.
+                foreach (var excludePathString in excludePathStrings)
+                {
+                    if (context.Request.Path.StartsWithSegments(excludePathString))
+                    {
+                        await next();
+                        return;
+                    }
+                }
+
+                // If we're building on demand, wait for that to finish, or raise any build errors
+                if (buildOnDemandTask != null)
+                {
+                    await buildOnDemandTask;
+                }
+
+                // It's no good if we try to return a 304. We need to capture the actual
+                // HTML content so it can be passed as a template to the prerenderer.
+                RemoveConditionalRequestHeaders(context.Request);
+
+                // Capture the non-prerendered responses, which in production will typically only
+                // be returning the default SPA index.html page (because other resources will be
+                // served statically from disk). We will use this as a template in which to inject
+                // the prerendered output.
+                using (var outputBuffer = new MemoryStream())
+                {
+                    var originalResponseStream = context.Response.Body;
+                    context.Response.Body = outputBuffer;
+
+                    try
+                    {
+                        await next();
+                        outputBuffer.Seek(0, SeekOrigin.Begin);
+                    }
+                    finally
+                    {
+                        context.Response.Body = originalResponseStream;
+                    }
+
+                    // If it's not a success response, we're not going to have any template HTML
+                    // to pass to the prerenderer.
+                    if (context.Response.StatusCode < 200 || context.Response.StatusCode >= 300)
+                    {
+                        var message = $"Prerendering failed because no HTML template could be obtained. " +
+                            $"Check that your SPA is compiling without errors. " +
+                            $"The {nameof(SpaApplicationBuilderExtensions.UseSpa)}() middleware returned " +
+                            $"a response with status code {context.Response.StatusCode}.";
+                        if (outputBuffer.Length > 0)
+                        {
+                            message += " and the following content: "
+                                + Encoding.UTF8.GetString(outputBuffer.GetBuffer());
+                        }
+
+                        throw new InvalidOperationException(message);
+                    }
+
+                    // Most prerendering logic will want to know about the original, unprerendered
+                    // HTML that the client would be getting otherwise. Typically this is used as
+                    // a template from which the fully prerendered page can be generated.
+                    var customData = new Dictionary<string, object>
+                    {
+                        { "originalHtml", Encoding.UTF8.GetString(outputBuffer.GetBuffer()) }
+                    };
+
+                    // If the developer wants to use custom logic to pass arbitrary data to the
+                    // prerendering JS code (e.g., to pass through cookie data), now's their chance
+                    options.SupplyData?.Invoke(context, customData);
+
+                    var (unencodedAbsoluteUrl, unencodedPathAndQuery)
+                        = GetUnencodedUrlAndPathQuery(context);
+                    var renderResult = await Prerenderer.RenderToString(
+                        applicationBasePath,
+                        nodeServices,
+                        applicationStoppingToken,
+                        moduleExport,
+                        unencodedAbsoluteUrl,
+                        unencodedPathAndQuery,
+                        customDataParameter: customData,
+                        timeoutMilliseconds: 0,
+                        requestPathBase: context.Request.PathBase.ToString());
+
+                    await ServePrerenderResult(context, renderResult);
+                }
+            });
+        }
+
+        private static void RemoveConditionalRequestHeaders(HttpRequest request)
+        {
+            request.Headers.Remove(HeaderNames.IfMatch);
+            request.Headers.Remove(HeaderNames.IfModifiedSince);
+            request.Headers.Remove(HeaderNames.IfNoneMatch);
+            request.Headers.Remove(HeaderNames.IfUnmodifiedSince);
+            request.Headers.Remove(HeaderNames.IfRange);
+        }
+
+        private static (string, string) GetUnencodedUrlAndPathQuery(HttpContext httpContext)
+        {
+            // This is a duplicate of code from Prerenderer.cs in the SpaServices package.
+            // Once the SpaServices.Extension package implementation gets merged back into
+            // SpaServices, this duplicate can be removed. To remove this, change the code
+            // above that calls Prerenderer.RenderToString to use the internal overload
+            // that takes an HttpContext instead of a url/path+query pair.
+            var requestFeature = httpContext.Features.Get<IHttpRequestFeature>();
+            var unencodedPathAndQuery = requestFeature.RawTarget;
+            var request = httpContext.Request;
+            var unencodedAbsoluteUrl = $"{request.Scheme}://{request.Host}{unencodedPathAndQuery}";
+            return (unencodedAbsoluteUrl, unencodedPathAndQuery);
+        }
+
+        private static async Task ServePrerenderResult(HttpContext context, RenderToStringResult renderResult)
+        {
+            context.Response.Clear();
+
+            if (!string.IsNullOrEmpty(renderResult.RedirectUrl))
+            {
+                context.Response.Redirect(renderResult.RedirectUrl);
+            }
+            else
+            {
+                // The Globals property exists for back-compatibility but is meaningless
+                // for prerendering that returns complete HTML pages
+                if (renderResult.Globals != null)
+                {
+                    throw new InvalidOperationException($"{nameof(renderResult.Globals)} is not " +
+                        $"supported when prerendering via {nameof(UseSpaPrerendering)}(). Instead, " +
+                        $"your prerendering logic should return a complete HTML page, in which you " +
+                        $"embed any information you wish to return to the client.");
+                }
+
+                context.Response.ContentType = "text/html";
+                await context.Response.WriteAsync(renderResult.Html);
+            }
+        }
+
+        private static INodeServices GetNodeServices(IServiceProvider serviceProvider)
+        {
+            // Use the registered instance, or create a new private instance if none is registered
+            var instance = (INodeServices)serviceProvider.GetService(typeof(INodeServices));
+            return instance ?? NodeServicesFactory.CreateNodeServices(
+                new NodeServicesOptions(serviceProvider));
+        }
+    }
+}

src/Microsoft.AspNetCore.SpaServices.Extensions/Prerendering/SpaPrerenderingOptions.cs

@@ -0,0 +1,43 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.SpaServices.Prerendering;
+using System;
+using System.Collections.Generic;
+
+namespace Microsoft.AspNetCore.Builder
+{
+    /// <summary>
+    /// Represents options for the SPA prerendering middleware.
+    /// </summary>
+    public class SpaPrerenderingOptions
+    {
+        /// <summary>
+        /// Gets or sets an <see cref="ISpaPrerendererBuilder"/> that the prerenderer will invoke before
+        /// looking for the boot module file.
+        /// 
+        /// This is only intended to be used during development as a way of generating the JavaScript boot
+        /// file automatically when the application runs. This property should be left as <c>null</c> in
+        /// production applications.
+        /// </summary>
+        public ISpaPrerendererBuilder BuildOnDemand { get; set; }
+
+        /// <summary>
+        /// Gets or sets the path, relative to your application root, of the JavaScript file
+        /// containing prerendering logic.
+        /// </summary>
+        public string BootModulePath { get; set; }
+
+        /// <summary>
+        /// Gets or sets an array of URL prefixes for which prerendering should not run.
+        /// </summary>
+        public string[] ExcludeUrls { get; set; }
+
+        /// <summary>
+        /// Gets or sets a callback that will be invoked during prerendering, allowing you to pass additional
+        /// data to the prerendering entrypoint code.
+        /// </summary>
+        public Action<HttpContext, IDictionary<string, object>> SupplyData { get; set; }
+    }
+}

src/Microsoft.AspNetCore.SpaServices.Extensions/Proxying/ConditionalProxyMiddleware.cs

@@ -0,0 +1,62 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Hosting;
+using System;
+using System.Net.Http;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Microsoft.AspNetCore.SpaServices.Extensions.Proxy
+{
+    // This duplicates and updates the proxying logic in SpaServices so that we can update
+    // the project templates without waiting for 2.1 to ship. When 2.1 is ready to ship,
+    // merge the additional proxying features (e.g., proxying websocket connections) back
+    // into the SpaServices proxying code. It's all internal.
+    internal class ConditionalProxyMiddleware
+    {
+        private readonly RequestDelegate _next;
+        private readonly Task<Uri> _baseUriTask;
+        private readonly string _pathPrefix;
+        private readonly bool _pathPrefixIsRoot;
+        private readonly HttpClient _httpClient;
+        private readonly CancellationToken _applicationStoppingToken;
+
+        public ConditionalProxyMiddleware(
+            RequestDelegate next,
+            string pathPrefix,
+            TimeSpan requestTimeout,
+            Task<Uri> baseUriTask,
+            IApplicationLifetime applicationLifetime)
+        {
+            if (!pathPrefix.StartsWith("/"))
+            {
+                pathPrefix = "/" + pathPrefix;
+            }
+
+            _next = next;
+            _pathPrefix = pathPrefix;
+            _pathPrefixIsRoot = string.Equals(_pathPrefix, "/", StringComparison.Ordinal);
+            _baseUriTask = baseUriTask;
+            _httpClient = SpaProxy.CreateHttpClientForProxy(requestTimeout);
+            _applicationStoppingToken = applicationLifetime.ApplicationStopping;
+        }
+
+        public async Task Invoke(HttpContext context)
+        {
+            if (context.Request.Path.StartsWithSegments(_pathPrefix) || _pathPrefixIsRoot)
+            {
+                var didProxyRequest = await SpaProxy.PerformProxyRequest(
+                    context, _httpClient, _baseUriTask, _applicationStoppingToken, proxy404s: false);
+                if (didProxyRequest)
+                {
+                    return;
+                }
+            }
+
+            // Not a request we can proxy
+            await _next.Invoke(context);
+        }
+    }
+}

src/Microsoft.AspNetCore.SpaServices.Extensions/Proxying/SpaProxy.cs

@@ -0,0 +1,288 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNetCore.Http;
+using System;
+using System.IO;
+using System.Linq;
+using System.Net;
+using System.Net.Http;
+using System.Net.WebSockets;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Microsoft.AspNetCore.SpaServices.Extensions.Proxy
+{
+    // This duplicates and updates the proxying logic in SpaServices so that we can update
+    // the project templates without waiting for 2.1 to ship. When 2.1 is ready to ship,
+    // remove the old ConditionalProxy.cs from SpaServices and replace its usages with this.
+    // Doesn't affect public API surface - it's all internal.
+    internal static class SpaProxy
+    {
+        private const int DefaultWebSocketBufferSize = 4096;
+        private const int StreamCopyBufferSize = 81920;
+
+        private static readonly string[] NotForwardedWebSocketHeaders = new[] { "Connection", "Host", "Upgrade", "Sec-WebSocket-Key", "Sec-WebSocket-Version" };
+
+        public static HttpClient CreateHttpClientForProxy(TimeSpan requestTimeout)
+        {
+            var handler = new HttpClientHandler
+            {
+                AllowAutoRedirect = false,
+                UseCookies = false,
+                
+            };
+
+            return new HttpClient(handler)
+            {
+                Timeout = requestTimeout
+            };
+        }
+
+        public static async Task<bool> PerformProxyRequest(
+            HttpContext context,
+            HttpClient httpClient,
+            Task<Uri> baseUriTask,
+            CancellationToken applicationStoppingToken,
+            bool proxy404s)
+        {
+            // Stop proxying if either the server or client wants to disconnect
+            var proxyCancellationToken = CancellationTokenSource.CreateLinkedTokenSource(
+                context.RequestAborted,
+                applicationStoppingToken).Token;
+
+            // We allow for the case where the target isn't known ahead of time, and want to
+            // delay proxied requests until the target becomes known. This is useful, for example,
+            // when proxying to Angular CLI middleware: we won't know what port it's listening
+            // on until it finishes starting up.
+            var baseUri = await baseUriTask;
+            var targetUri = new Uri(
+                baseUri,
+                context.Request.Path + context.Request.QueryString);
+
+            try
+            {
+                if (context.WebSockets.IsWebSocketRequest)
+                {
+                    await AcceptProxyWebSocketRequest(context, ToWebSocketScheme(targetUri), proxyCancellationToken);
+                    return true;
+                }
+                else
+                {
+                    using (var requestMessage = CreateProxyHttpRequest(context, targetUri))
+                    using (var responseMessage = await httpClient.SendAsync(
+                        requestMessage,
+                        HttpCompletionOption.ResponseHeadersRead,
+                        proxyCancellationToken))
+                    {
+                        if (!proxy404s)
+                        {
+                            if (responseMessage.StatusCode == HttpStatusCode.NotFound)
+                            {
+                                // We're not proxying 404s, i.e., we want to resume the middleware pipeline
+                                // and let some other middleware handle this.
+                                return false;
+                            }
+                        }
+
+                        await CopyProxyHttpResponse(context, responseMessage, proxyCancellationToken);
+                        return true;
+                    }
+                }
+            }
+            catch (OperationCanceledException)
+            {
+                // If we're aborting because either the client disconnected, or the server
+                // is shutting down, don't treat this as an error.
+                return true;
+            }
+            catch (IOException)
+            {
+                // This kind of exception can also occur if a proxy read/write gets interrupted
+                // due to the process shutting down.
+                return true;
+            }
+            catch (HttpRequestException ex)
+            {
+                throw new HttpRequestException(
+                    $"Failed to proxy the request to {targetUri.ToString()}, because the request to " +
+                    $"the proxy target failed. Check that the proxy target server is running and " +
+                    $"accepting requests to {baseUri.ToString()}.\n\n" +
+                    $"The underlying exception message was '{ex.Message}'." +
+                    $"Check the InnerException for more details.", ex);
+            }
+        }
+
+        private static HttpRequestMessage CreateProxyHttpRequest(HttpContext context, Uri uri)
+        {
+            var request = context.Request;
+
+            var requestMessage = new HttpRequestMessage();
+            var requestMethod = request.Method;
+            if (!HttpMethods.IsGet(requestMethod) &&
+                !HttpMethods.IsHead(requestMethod) &&
+                !HttpMethods.IsDelete(requestMethod) &&
+                !HttpMethods.IsTrace(requestMethod))
+            {
+                var streamContent = new StreamContent(request.Body);
+                requestMessage.Content = streamContent;
+            }
+
+            // Copy the request headers
+            foreach (var header in request.Headers)
+            {
+                if (!requestMessage.Headers.TryAddWithoutValidation(header.Key, header.Value.ToArray()) && requestMessage.Content != null)
+                {
+                    requestMessage.Content?.Headers.TryAddWithoutValidation(header.Key, header.Value.ToArray());
+                }
+            }
+
+            requestMessage.Headers.Host = uri.Authority;
+            requestMessage.RequestUri = uri;
+            requestMessage.Method = new HttpMethod(request.Method);
+
+            return requestMessage;
+        }
+
+        private static async Task CopyProxyHttpResponse(HttpContext context, HttpResponseMessage responseMessage, CancellationToken cancellationToken)
+        {
+            context.Response.StatusCode = (int)responseMessage.StatusCode;
+            foreach (var header in responseMessage.Headers)
+            {
+                context.Response.Headers[header.Key] = header.Value.ToArray();
+            }
+
+            foreach (var header in responseMessage.Content.Headers)
+            {
+                context.Response.Headers[header.Key] = header.Value.ToArray();
+            }
+
+            // SendAsync removes chunking from the response. This removes the header so it doesn't expect a chunked response.
+            context.Response.Headers.Remove("transfer-encoding");
+
+            using (var responseStream = await responseMessage.Content.ReadAsStreamAsync())
+            {
+                await responseStream.CopyToAsync(context.Response.Body, StreamCopyBufferSize, cancellationToken);
+            }
+        }
+
+        private static Uri ToWebSocketScheme(Uri uri)
+        {
+            if (uri == null)
+            {
+                throw new ArgumentNullException(nameof(uri));
+            }
+
+            var uriBuilder = new UriBuilder(uri);
+            if (string.Equals(uriBuilder.Scheme, "https", StringComparison.OrdinalIgnoreCase))
+            {
+                uriBuilder.Scheme = "wss";
+            }
+            else if (string.Equals(uriBuilder.Scheme, "http", StringComparison.OrdinalIgnoreCase))
+            {
+                uriBuilder.Scheme = "ws";
+            }
+
+            return uriBuilder.Uri;
+        }
+
+        private static async Task<bool> AcceptProxyWebSocketRequest(HttpContext context, Uri destinationUri, CancellationToken cancellationToken)
+        {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            if (destinationUri == null)
+            {
+                throw new ArgumentNullException(nameof(destinationUri));
+            }
+
+            using (var client = new ClientWebSocket())
+            {
+                foreach (var headerEntry in context.Request.Headers)
+                {
+                    if (!NotForwardedWebSocketHeaders.Contains(headerEntry.Key, StringComparer.OrdinalIgnoreCase))
+                    {
+                        client.Options.SetRequestHeader(headerEntry.Key, headerEntry.Value);
+                    }
+                }
+
+                try
+                {
+                    // Note that this is not really good enough to make Websockets work with
+                    // Angular CLI middleware. For some reason, ConnectAsync takes over 1 second,
+                    // on Windows, by which time the logic in SockJS has already timed out and made
+                    // it fall back on some other transport (xhr_streaming, usually). It's fine
+                    // on Linux though, completing almost instantly.
+                    // 
+                    // The slowness on Windows does not cause a problem though, because the transport
+                    // fallback logic works correctly and doesn't surface any errors, but it would be
+                    // better if ConnectAsync was fast enough and the initial Websocket transport
+                    // could actually be used.
+                    await client.ConnectAsync(destinationUri, cancellationToken);
+                }
+                catch (WebSocketException)
+                {
+                    context.Response.StatusCode = 400;
+                    return false;
+                }
+
+                using (var server = await context.WebSockets.AcceptWebSocketAsync(client.SubProtocol))
+                {
+                    var bufferSize = DefaultWebSocketBufferSize;
+                    await Task.WhenAll(
+                        PumpWebSocket(client, server, bufferSize, cancellationToken),
+                        PumpWebSocket(server, client, bufferSize, cancellationToken));
+                }
+
+                return true;
+            }
+        }
+
+        private static async Task PumpWebSocket(WebSocket source, WebSocket destination, int bufferSize, CancellationToken cancellationToken)
+        {
+            if (bufferSize <= 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(bufferSize));
+            }
+
+            var buffer = new byte[bufferSize];
+
+            while (true)
+            {
+                // Because WebSocket.ReceiveAsync doesn't work well with CancellationToken (it doesn't
+                // actually exit when the token notifies, at least not in the 'server' case), use
+                // polling. The perf might not be ideal, but this is a dev-time feature only.
+                var resultTask = source.ReceiveAsync(new ArraySegment<byte>(buffer), cancellationToken);
+                while (true)
+                {
+                    if (cancellationToken.IsCancellationRequested)
+                    {
+                        return;
+                    }
+
+                    if (resultTask.IsCompleted)
+                    {
+                        break;
+                    }
+
+                    await Task.Delay(100);
+                }
+
+                var result = resultTask.Result; // We know it's completed already
+                if (result.MessageType == WebSocketMessageType.Close)
+                {
+                    if (destination.State == WebSocketState.Open || destination.State == WebSocketState.CloseReceived)
+                    {
+                        await destination.CloseOutputAsync(source.CloseStatus.Value, source.CloseStatusDescription, cancellationToken);
+                    }
+
+                    return;
+                }
+
+                await destination.SendAsync(new ArraySegment<byte>(buffer, 0, result.Count), result.MessageType, result.EndOfMessage, cancellationToken);
+            }
+        }
+    }
+}

src/Microsoft.AspNetCore.SpaServices.Extensions/Proxying/SpaProxyingExtensions.cs

@@ -0,0 +1,92 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.SpaServices;
+using Microsoft.AspNetCore.SpaServices.Extensions.Proxy;
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Microsoft.AspNetCore.Builder
+{
+    /// <summary>
+    /// Extension methods for proxying requests to a local SPA development server during
+    /// development. Not for use in production applications.
+    /// </summary>
+    public static class SpaProxyingExtensions
+    {
+        /// <summary>
+        /// Configures the application to forward incoming requests to a local Single Page
+        /// Application (SPA) development server. This is only intended to be used during
+        /// development. Do not enable this middleware in production applications.
+        /// </summary>
+        /// <param name="spaBuilder">The <see cref="ISpaBuilder"/>.</param>
+        /// <param name="baseUri">The target base URI to which requests should be proxied.</param>
+        public static void UseProxyToSpaDevelopmentServer(
+            this ISpaBuilder spaBuilder,
+            string baseUri)
+        {
+            UseProxyToSpaDevelopmentServer(
+                spaBuilder,
+                new Uri(baseUri));
+        }
+
+        /// <summary>
+        /// Configures the application to forward incoming requests to a local Single Page
+        /// Application (SPA) development server. This is only intended to be used during
+        /// development. Do not enable this middleware in production applications.
+        /// </summary>
+        /// <param name="spaBuilder">The <see cref="ISpaBuilder"/>.</param>
+        /// <param name="baseUri">The target base URI to which requests should be proxied.</param>
+        public static void UseProxyToSpaDevelopmentServer(
+            this ISpaBuilder spaBuilder,
+            Uri baseUri)
+        {
+            UseProxyToSpaDevelopmentServer(
+                spaBuilder,
+                Task.FromResult(baseUri));
+        }
+
+        /// <summary>
+        /// Configures the application to forward incoming requests to a local Single Page
+        /// Application (SPA) development server. This is only intended to be used during
+        /// development. Do not enable this middleware in production applications.
+        /// </summary>
+        /// <param name="spaBuilder">The <see cref="ISpaBuilder"/>.</param>
+        /// <param name="baseUriTask">A <see cref="Task"/> that resolves with the target base URI to which requests should be proxied.</param>
+        public static void UseProxyToSpaDevelopmentServer(
+            this ISpaBuilder spaBuilder,
+            Task<Uri> baseUriTask)
+        {
+            var applicationBuilder = spaBuilder.ApplicationBuilder;
+            var applicationStoppingToken = GetStoppingToken(applicationBuilder);
+
+            // Since we might want to proxy WebSockets requests (e.g., by default, AngularCliMiddleware
+            // requires it), enable it for the app
+            applicationBuilder.UseWebSockets();
+
+            // It's important not to time out the requests, as some of them might be to
+            // server-sent event endpoints or similar, where it's expected that the response
+            // takes an unlimited time and never actually completes
+            var neverTimeOutHttpClient =
+                SpaProxy.CreateHttpClientForProxy(Timeout.InfiniteTimeSpan);
+
+            // Proxy all requests into the Angular CLI server
+            applicationBuilder.Use(async (context, next) =>
+            {
+                var didProxyRequest = await SpaProxy.PerformProxyRequest(
+                    context, neverTimeOutHttpClient, baseUriTask, applicationStoppingToken,
+                    proxy404s: true);
+            });
+        }
+
+        private static CancellationToken GetStoppingToken(IApplicationBuilder appBuilder)
+        {
+            var applicationLifetime = appBuilder
+                .ApplicationServices
+                .GetService(typeof(IApplicationLifetime));
+            return ((IApplicationLifetime)applicationLifetime).ApplicationStopping;
+        }
+    }
+}

src/Microsoft.AspNetCore.SpaServices.Extensions/SpaApplicationBuilderExtensions.cs

@@ -0,0 +1,46 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNetCore.SpaServices;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Options;
+using System;
+
+namespace Microsoft.AspNetCore.Builder
+{
+    /// <summary>
+    /// Provides extension methods used for configuring an application to
+    /// host a client-side Single Page Application (SPA).
+    /// </summary>
+    public static class SpaApplicationBuilderExtensions
+    {
+        /// <summary>
+        /// Handles all requests from this point in the middleware chain by returning
+        /// the default page for the Single Page Application (SPA).
+        /// 
+        /// This middleware should be placed late in the chain, so that other middleware
+        /// for serving static files, MVC actions, etc., takes precedence.
+        /// </summary>
+        /// <param name="app">The <see cref="IApplicationBuilder"/>.</param>
+        /// <param name="configuration">
+        /// This callback will be invoked so that additional middleware can be registered within
+        /// the context of this SPA.
+        /// </param>
+        public static void UseSpa(this IApplicationBuilder app, Action<ISpaBuilder> configuration)
+        {
+            if (configuration == null)
+            {
+                throw new ArgumentNullException(nameof(configuration));
+            }
+
+            // Use the options configured in DI (or blank if none was configured). We have to clone it
+            // otherwise if you have multiple UseSpa calls, their configurations would interfere with one another.
+            var optionsProvider = app.ApplicationServices.GetService<IOptions<SpaOptions>>();
+            var options = new SpaOptions(optionsProvider.Value);
+
+            var spaBuilder = new DefaultSpaBuilder(app, options);
+            configuration.Invoke(spaBuilder);
+            SpaDefaultPageMiddleware.Attach(spaBuilder);
+        }
+    }
+}

src/Microsoft.AspNetCore.SpaServices.Extensions/SpaDefaultPageMiddleware.cs

@@ -0,0 +1,58 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Hosting;
+using System;
+
+namespace Microsoft.AspNetCore.SpaServices
+{
+    internal class SpaDefaultPageMiddleware
+    {
+        public static void Attach(ISpaBuilder spaBuilder)
+        {
+            if (spaBuilder == null)
+            {
+                throw new ArgumentNullException(nameof(spaBuilder));
+            }
+
+            var app = spaBuilder.ApplicationBuilder;
+            var options = spaBuilder.Options;
+
+            // Rewrite all requests to the default page
+            app.Use((context, next) =>
+            {
+                context.Request.Path = options.DefaultPage;
+                return next();
+            });
+
+            // Serve it as file from wwwroot (by default), or any other configured file provider
+            app.UseStaticFiles(new StaticFileOptions
+            {
+                FileProvider = options.DefaultPageFileProvider
+            });
+
+            // If the default file didn't get served as a static file (usually because it was not
+            // present on disk), the SPA is definitely not going to work.
+            app.Use((context, next) =>
+            {
+                var message = "The SPA default page middleware could not return the default page " +
+                    $"'{options.DefaultPage}' because it was not found, and no other middleware " +
+                    "handled the request.\n";
+
+                // Try to clarify the common scenario where someone runs an application in
+                // Production environment without first publishing the whole application
+                // or at least building the SPA.
+                var hostEnvironment = (IHostingEnvironment)context.RequestServices.GetService(typeof(IHostingEnvironment));
+                if (hostEnvironment != null && hostEnvironment.IsProduction())
+                {
+                    message += "Your application is running in Production mode, so make sure it has " +
+                        "been published, or that you have built your SPA manually. Alternatively you " +
+                        "may wish to switch to the Development environment.\n";
+                }
+
+                throw new InvalidOperationException(message);
+            });
+        }
+    }
+}

src/Microsoft.AspNetCore.SpaServices.Extensions/SpaOptions.cs

@@ -0,0 +1,71 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.FileProviders;
+using System;
+
+namespace Microsoft.AspNetCore.SpaServices
+{
+    /// <summary>
+    /// Describes options for hosting a Single Page Application (SPA).
+    /// </summary>
+    public class SpaOptions
+    {
+        private PathString _defaultPage = "/index.html";
+
+        /// <summary>
+        /// Constructs a new instance of <see cref="SpaOptions"/>.
+        /// </summary>
+        public SpaOptions()
+        {
+        }
+
+        /// <summary>
+        /// Constructs a new instance of <see cref="SpaOptions"/>.
+        /// </summary>
+        /// <param name="copyFromOptions">An instance of <see cref="SpaOptions"/> from which values should be copied.</param>
+        internal SpaOptions(SpaOptions copyFromOptions)
+        {
+            _defaultPage = copyFromOptions.DefaultPage;
+            DefaultPageFileProvider = copyFromOptions.DefaultPageFileProvider;
+            SourcePath = copyFromOptions.SourcePath;
+        }
+
+        /// <summary>
+        /// Gets or sets the URL of the default page that hosts your SPA user interface.
+        /// The default value is <c>"/index.html"</c>.
+        /// </summary>
+        public PathString DefaultPage
+        {
+            get => _defaultPage;
+            set
+            {
+                if (string.IsNullOrEmpty(value.Value))
+                {
+                    throw new ArgumentNullException($"The value for {nameof(DefaultPage)} cannot be null or empty.");
+                }
+
+                _defaultPage = value;
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets the <see cref="IFileProvider"/> that supplies content
+        /// for serving the SPA's default page.
+        /// 
+        /// If not set, a default file provider will read files from the
+        /// <see cref="IHostingEnvironment.WebRootPath"/>, which by default is
+        /// the <c>wwwroot</c> directory.
+        /// </summary>
+        public IFileProvider DefaultPageFileProvider { get; set; }
+
+        /// <summary>
+        /// Gets or sets the path, relative to the application working directory,
+        /// of the directory that contains the SPA source files during
+        /// development. The directory may not exist in published applications.
+        /// </summary>
+        public string SourcePath { get; set; }
+    }
+}