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/Npm/NpmScriptRunner.cs

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