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

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);
+        }
+    }
+}