Eliminate the NodeHostingModel enum because it isn't extensible. Instead, use extension methods on NodeServicesOptions to configure a NodeInstanceFactory.

samples/misc/LatencyTest/Program.cs

@@ -16,7 +16,6 @@ namespace ConsoleApplication
             // Set up the DI system
             var services = new ServiceCollection();
             services.AddNodeServices(options => {
-                options.HostingModel = NodeServicesOptions.DefaultNodeHostingModel;
                 options.ProjectPath = Directory.GetCurrentDirectory();
                 options.WatchFileExtensions = new string[] {}; // Don't watch anything
             });

src/Microsoft.AspNetCore.NodeServices/Configuration/NodeHostingModel.cs

@@ -1,18 +0,0 @@
-namespace Microsoft.AspNetCore.NodeServices
-{
-    /// <summary>
-    /// Represents a way of creating and invoking code in a Node.js environment.
-    /// </summary>
-    public enum NodeHostingModel
-    {
-        /// <summary>
-        /// An out-of-process Node.js instance where RPC calls are made via HTTP.
-        /// </summary>
-        Http,
-
-        /// <summary>
-        /// An out-of-process Node.js instance where RPC calls are made over binary sockets.
-        /// </summary>
-        Socket,
-    }
-}

src/Microsoft.AspNetCore.NodeServices/Configuration/NodeServicesFactory.cs

@@ -1,5 +1,4 @@
 using System;
-using Microsoft.AspNetCore.NodeServices.HostingModels;
 
 namespace Microsoft.AspNetCore.NodeServices
 {
@@ -20,32 +19,7 @@ namespace Microsoft.AspNetCore.NodeServices
                 throw new ArgumentNullException(nameof (options));
             }
 
-            return new NodeServicesImpl(() => CreateNodeInstance(options));
+            return new NodeServicesImpl(options.NodeInstanceFactory);
-        }
-
-        private static INodeInstance CreateNodeInstance(NodeServicesOptions options)
-        {
-            if (options.NodeInstanceFactory != null)
-            {
-                // If you've explicitly supplied an INodeInstance factory, we'll use that. This is useful for
-                // custom INodeInstance implementations.
-                return options.NodeInstanceFactory();
-            }
-            else
-            {
-                switch (options.HostingModel)
-                {
-                    case NodeHostingModel.Http:
-                        return new HttpNodeInstance(options.ProjectPath, options.WatchFileExtensions, options.NodeInstanceOutputLogger, 
-                            options.EnvironmentVariables, options.InvocationTimeoutMilliseconds, options.LaunchWithDebugging, options.DebuggingPort, /* port */ 0);
-                    case NodeHostingModel.Socket:
-                        var pipeName = "pni-" + Guid.NewGuid().ToString("D"); // Arbitrary non-clashing string
-                        return new SocketNodeInstance(options.ProjectPath, options.WatchFileExtensions, pipeName, options.NodeInstanceOutputLogger,
-                            options.EnvironmentVariables, options.InvocationTimeoutMilliseconds, options.LaunchWithDebugging, options.DebuggingPort);
-                    default:
-                        throw new ArgumentException("Unknown hosting model: " + options.HostingModel);
-                }
-            }
         }
     }
 }

src/Microsoft.AspNetCore.NodeServices/Configuration/NodeServicesOptions.cs

@@ -13,11 +13,6 @@ namespace Microsoft.AspNetCore.NodeServices
     /// </summary>
     public class NodeServicesOptions
     {
-        /// <summary>
-        /// Defines the default <see cref="NodeHostingModel"/>.
-        /// </summary>
-        public const NodeHostingModel DefaultNodeHostingModel = NodeHostingModel.Http;
-
         internal const string TimeoutConfigPropertyName = nameof(InvocationTimeoutMilliseconds);
         private const int DefaultInvocationTimeoutMilliseconds = 60 * 1000;
         private const string LogCategoryName = "Microsoft.AspNetCore.NodeServices";
@@ -36,7 +31,6 @@ namespace Microsoft.AspNetCore.NodeServices
 
             EnvironmentVariables = new Dictionary<string, string>();
             InvocationTimeoutMilliseconds = DefaultInvocationTimeoutMilliseconds;
-            HostingModel = DefaultNodeHostingModel;
             WatchFileExtensions = (string[])DefaultWatchFileExtensions.Clone();
 
             // In an ASP.NET environment, we can use the IHostingEnvironment data to auto-populate a few
@@ -53,15 +47,15 @@ namespace Microsoft.AspNetCore.NodeServices
             NodeInstanceOutputLogger = loggerFactory != null
                 ? loggerFactory.CreateLogger(LogCategoryName)
                 : new ConsoleLogger(LogCategoryName, null, false);
+
+            // By default, we use this package's built-in out-of-process-via-HTTP hosting/transport
+            this.UseHttpHosting();
         }
 
         /// <summary>
-        /// Specifies which <see cref="NodeHostingModel"/> should be used.
+        /// Specifies how to construct Node.js instances. An <see cref="INodeInstance"/> encapsulates all details about
-        /// </summary>
+        /// how Node.js instances are launched and communicated with. A new <see cref="INodeInstance"/> will be created
-        public NodeHostingModel HostingModel { get; set; }
+        /// automatically if the previous instance has terminated (e.g., because a source file changed).
-
-        /// <summary>
-        /// If set, this callback function will be invoked to supply the <see cref="INodeServices"/> instance.
         /// </summary>
         public Func<INodeInstance> NodeInstanceFactory { get; set; }
 

src/Microsoft.AspNetCore.NodeServices/HostingModels/HttpNodeInstance.cs

@@ -1,12 +1,10 @@
 using System;
-using System.Collections.Generic;
 using System.IO;
 using System.Net.Http;
 using System.Text;
 using System.Text.RegularExpressions;
 using System.Threading;
 using System.Threading.Tasks;
-using Microsoft.Extensions.Logging;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Serialization;
 
@@ -36,21 +34,19 @@ namespace Microsoft.AspNetCore.NodeServices.HostingModels
         private bool _disposed;
         private int _portNumber;
 
-        public HttpNodeInstance(string projectPath, string[] watchFileExtensions, ILogger nodeInstanceOutputLogger,
+        public HttpNodeInstance(NodeServicesOptions options, int port = 0)
-            IDictionary<string, string> environmentVars, int invocationTimeoutMilliseconds, bool launchWithDebugging,
-            int debuggingPort, int port = 0)
         : base(
                 EmbeddedResourceReader.Read(
                     typeof(HttpNodeInstance),
                     "/Content/Node/entrypoint-http.js"),
-                projectPath,
+                options.ProjectPath,
-                watchFileExtensions,
+                options.WatchFileExtensions,
                 MakeCommandLineOptions(port),
-                nodeInstanceOutputLogger,
+                options.NodeInstanceOutputLogger,
-                environmentVars,
+                options.EnvironmentVariables,
-                invocationTimeoutMilliseconds,
+                options.InvocationTimeoutMilliseconds,
-                launchWithDebugging,
+                options.LaunchWithDebugging,
-                debuggingPort)
+                options.DebuggingPort)
         {
             _client = new HttpClient();
         }

src/Microsoft.AspNetCore.NodeServices/HostingModels/NodeServicesOptionsExtensions.cs

@@ -0,0 +1,30 @@
+using System;
+
+namespace Microsoft.AspNetCore.NodeServices.HostingModels
+{
+    /// <summary>
+    /// Extension methods that help with populating a <see cref="NodeServicesOptions"/> object.
+    /// </summary>
+    public static class NodeServicesOptionsExtensions
+    {
+        /// <summary>
+        /// Configures the <see cref="INodeServices"/> service so that it will use out-of-process
+        /// Node.js instances and perform RPC calls over HTTP.
+        /// </summary>
+        public static void UseHttpHosting(this NodeServicesOptions options)
+        {
+            options.NodeInstanceFactory = () => new HttpNodeInstance(options);
+        }
+
+        /// <summary>
+        /// Configures the <see cref="INodeServices"/> service so that it will use out-of-process
+        /// Node.js instances and perform RPC calls over binary sockets (on Windows, this is
+        /// implemented as named pipes; on other platforms it uses domain sockets).
+        /// </summary>
+        public static void UseSocketHosting(this NodeServicesOptions options)
+        {
+            var pipeName = "pni-" + Guid.NewGuid().ToString("D"); // Arbitrary non-clashing string
+            options.NodeInstanceFactory = () => new SocketNodeInstance(options, pipeName);
+        }
+    }
+}

src/Microsoft.AspNetCore.NodeServices/HostingModels/SocketNodeInstance.cs

@@ -42,21 +42,19 @@ namespace Microsoft.AspNetCore.NodeServices.HostingModels
         private string _socketAddress;
         private VirtualConnectionClient _virtualConnectionClient;
 
-        public SocketNodeInstance(string projectPath, string[] watchFileExtensions, string socketAddress,
+        public SocketNodeInstance(NodeServicesOptions options, string socketAddress)
-            ILogger nodeInstanceOutputLogger, IDictionary<string, string> environmentVars,
-            int invocationTimeoutMilliseconds, bool launchWithDebugging, int debuggingPort)
         : base(
                 EmbeddedResourceReader.Read(
                     typeof(SocketNodeInstance),
                     "/Content/Node/entrypoint-socket.js"),
-                projectPath,
+                options.ProjectPath,
-                watchFileExtensions,
+                options.WatchFileExtensions,
                 MakeNewCommandLineOptions(socketAddress),
-                nodeInstanceOutputLogger,
+                options.NodeInstanceOutputLogger,
-                environmentVars,
+                options.EnvironmentVariables,
-                invocationTimeoutMilliseconds,
+                options.InvocationTimeoutMilliseconds,
-                launchWithDebugging,
+                options.LaunchWithDebugging,
-                debuggingPort)
+                options.DebuggingPort)
         {
             _socketAddress = socketAddress;
         }

src/Microsoft.AspNetCore.NodeServices/NodeServicesImpl.cs

@@ -50,7 +50,7 @@ namespace Microsoft.AspNetCore.NodeServices
             return InvokeExportWithPossibleRetryAsync<T>(moduleName, exportedFunctionName, args, /* allowRetry */ true, cancellationToken);
         }
 
-        public async Task<T> InvokeExportWithPossibleRetryAsync<T>(string moduleName, string exportedFunctionName, object[] args, bool allowRetry, CancellationToken cancellationToken)
+        private async Task<T> InvokeExportWithPossibleRetryAsync<T>(string moduleName, string exportedFunctionName, object[] args, bool allowRetry, CancellationToken cancellationToken)
         {
             ThrowAnyOutstandingDelayedDisposalException();
             var nodeInstance = GetOrCreateCurrentNodeInstance();