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/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);
+                }
+            }
+        }
+    }
+}