Sketch Node.js service "building".

src/Microsoft.Tye.Core/ApplicationFactory.cs

@@ -337,6 +337,18 @@ namespace Microsoft.Tye
                         var external = new ExternalServiceBuilder(configService.Name, ServiceSource.Configuration);
                         service = external;
                     }
+                    else if (configService.Node != null)
+                    {
+                        string packagePath = Path.GetFullPath(Path.Combine(config.Source.Directory!.FullName, configService.Node.Package));
+
+                        var node = new NodeServiceBuilder(configService.Name, packagePath, ServiceSource.Configuration)
+                        {
+                            Replicas = configService.Replicas ?? 1,
+                            Script = configService.Node.Script
+                        };
+
+                        service = node;
+                    }
                     else
                     {
                         throw new CommandException("Unable to determine service type.");

src/Microsoft.Tye.Core/ConfigModel/ConfigNode.cs

@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel.DataAnnotations;
+
+namespace Microsoft.Tye.ConfigModel
+{
+    public class ConfigNode
+    {
+        [Required]
+        public string Package { get; set; } = default!;
+
+        public string? Script { get; set; } = default!;
+    }
+}

src/Microsoft.Tye.Core/ConfigModel/ConfigService.cs

@@ -46,5 +46,6 @@ namespace Microsoft.Tye.ConfigModel
         public string? Version { get; set; }
         public string? Architecture { get; set; }
         public string? CloneDirectory { get; internal set; }
+        public ConfigNode? Node { get; set; }
     }
 }

src/Microsoft.Tye.Core/NodeServiceBuilder.cs

@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+
+namespace Microsoft.Tye
+{
+    public class NodeServiceBuilder : LaunchedServiceBuilder
+    {
+        public NodeServiceBuilder(string name, string packagePath, ServiceSource source)
+            : base(name, source)
+        {
+            PackagePath = packagePath;
+        }
+
+        public string PackagePath { get; set; }
+
+        public string? Script { get; set; }
+    }
+}

src/Microsoft.Tye.Core/Serialization/ConfigServiceParser.cs

@@ -165,6 +165,10 @@ namespace Tye.Serialization
                     case "cloneDirectory":
                         service.CloneDirectory = YamlParser.GetScalarValue(key, child.Value);
                         break;
+                    case "node":
+                        service.Node = new ConfigNode();
+                        HandleNode((YamlMappingNode)child.Value, service.Node);
+                        break;
                     default:
                         throw new TyeYamlException(child.Key.Start, CoreStrings.FormatUnrecognizedKey(key));
                 }
@@ -235,6 +239,35 @@ namespace Tye.Serialization
             }
         }
 
+        private static void HandleNode(YamlSequenceNode yamlSequenceNode, ConfigNode node)
+        {
+            foreach (var child in yamlSequenceNode.Children)
+            {
+                YamlParser.ThrowIfNotYamlMapping(child);
+                HandleNode((YamlMappingNode)child, node);
+            }
+        }
+
+        private static void HandleNode(YamlMappingNode yamlMappingNode, ConfigNode node)
+        {
+            foreach (var child in yamlMappingNode.Children)
+            {
+                var key = YamlParser.GetScalarValue(child.Key);
+
+                switch (key)
+                {
+                    case "package":
+                        node.Package =  YamlParser.GetScalarValue("package", child.Value);
+                        break;
+                    case "script":
+                        node.Script =  YamlParser.GetScalarValue("script", child.Value);
+                        break;
+                    default:
+                        throw new TyeYamlException(child.Key.Start, CoreStrings.FormatUnrecognizedKey(key));
+                }
+            }
+        }
+
         private static void HandleServiceProbe(YamlMappingNode yamlMappingNode, ConfigProbe probe)
         {
             foreach (var child in yamlMappingNode.Children)

src/tye/ApplicationBuilderExtensions.cs

@@ -152,6 +152,35 @@ namespace Microsoft.Tye
                     liveness = null;
                     readiness = null;
                 }
+                else if (service is NodeServiceBuilder node)
+                {
+                    string executablePath = "node";
+                    string? workingDirectory = Path.GetDirectoryName(node.PackagePath);
+
+                    var input = new StringReader(File.ReadAllText(node.PackagePath));
+
+                    var yaml = new YamlDotNet.RepresentationModel.YamlStream();
+
+                    yaml.Load(input);
+
+                    var mapping = (YamlDotNet.RepresentationModel.YamlMappingNode)yaml.Documents[0].RootNode;
+
+                    var mainNode = (YamlDotNet.RepresentationModel.YamlScalarNode)mapping.Children[new YamlDotNet.RepresentationModel.YamlScalarNode("main")];
+
+                    var main = mainNode.Value;
+
+                    string args = $"{main}";
+
+                    runInfo = new ExecutableRunInfo(executablePath, workingDirectory, args);
+                    replicas = node.Replicas;
+                    liveness = null;
+                    readiness = null;
+
+                    foreach (var entry in node.EnvironmentVariables)
+                    {
+                        env.Add(entry.ToHostingEnvironmentVariable());
+                    }
+                }
                 else
                 {
                     throw new InvalidOperationException($"Cannot figure out how to run service '{service.Name}'.");