Print error if there are no runnable services in the application. (#193)

src/tye/BuildHost.cs

@@ -15,6 +15,12 @@ namespace Microsoft.Tye
         {
             var output = new OutputContext(console, verbosity);
             var application = await ApplicationFactory.CreateAsync(output, path);
+
+            if (application.Services.Count == 0)
+            {
+                throw new CommandException($"No services found in \"{application.Source.Name}\"");
+            }
+
             await ExecuteBuildAsync(output, application, environment: "production", interactive);
         }
 

src/tye/Program.DeployCommand.cs

@@ -39,6 +39,12 @@ namespace Microsoft.Tye
 
                 var output = new OutputContext(console, verbosity);
                 var application = await ApplicationFactory.CreateAsync(output, path);
+
+                if (application.Services.Count == 0)
+                {
+                    throw new CommandException($"No services found in \"{application.Source.Name}\"");
+                }
+
                 await ExecuteDeployAsync(new OutputContext(console, verbosity), application, environment: "production", interactive, force);
             });
 

src/tye/Program.RunCommand.cs

@@ -5,6 +5,7 @@
 using System;
 using System.CommandLine;
 using System.CommandLine.Invocation;
+using System.CommandLine.IO;
 using System.IO;
 using System.Threading;
 using Microsoft.Tye.ConfigModel;
@@ -76,6 +77,11 @@ namespace Microsoft.Tye
 
                 InitializeThreadPoolSettings(serviceCount);
 
+                if (application.Services.Count == 0)
+                {
+                    throw new CommandException($"No services found in \"{application.Source.Name}\"");
+                }
+
                 using var host = new TyeHost(application.ToHostingApplication(), args, debug);
                 await host.RunAsync();
             });