Return a result from an up action

lib/proto/gen/plugin/plugin_server_pb.rb

@@ -0,0 +1,18 @@
+# Generated by the protocol buffer compiler.  DO NOT EDIT!
+# source: plugin_server.proto
+
+require 'google/protobuf'
+
+Google::Protobuf::DescriptorPool.generated_pool.build do
+  add_file("plugin_server.proto", :syntax => :proto3) do
+    add_message "hashicorp.vagrant.UpResult" do
+      optional :success, :bool, 1
+    end
+  end
+end
+
+module Hashicorp
+  module Vagrant
+    UpResult = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("hashicorp.vagrant.UpResult").msgclass
+  end
+end

lib/proto/plugin_server.proto

@@ -0,0 +1,8 @@
+syntax = "proto3";
+
+package hashicorp.vagrant;
+
+message UpResult {
+  bool success = 1;
+}
+

plugins/README.md

@@ -3,3 +3,9 @@
 These are plugins that ship with Vagrant. Vagrant core uses its own
 plugin system to power a lot of the core pieces that ship with Vagrant.
 Each plugin will have its own README which explains its specific role.
+
+## Generate proto
+
+```
+grpc_tools_ruby_protoc -I . --ruby_out=gen/plugin --grpc_out=gen/plugin ./plugin_server.proto
+```

plugins/commands/serve/service/provider_service.rb

@@ -1,6 +1,7 @@
 
 require 'proto/gen/plugin/plugin_pb'
 require 'proto/gen/plugin/plugin_services_pb'
+require 'proto/gen/plugin/plugin_server_pb'
 require 'vagrant/machine'
 require 'logger'
 
@@ -37,6 +38,7 @@ module VagrantPlugins
         def action_up(req, _unused_call)
           machine = machine_arg_to_machine(req)
           LOG.debug(machine)
+          Hashicorp::Vagrant::UpResult.new(success: true)
         end
 
         def machine_arg_to_machine(req)
@@ -60,8 +62,12 @@ module VagrantPlugins
             ),
           ]
           result = [
-            nil,
+            Hashicorp::Vagrant::Sdk::FuncSpec::Value.new(
+              type: "hashicorp.vagrant.UpResult",
+              name: ""
+            ),
           ]
+          
           Hashicorp::Vagrant::Sdk::FuncSpec.new(
             args: args,
             result: result