Add serve helper function.

Add a helper that will stand up the go-plugin server for us.

I made it require a name for the provider because I think having that
information will be useful to us down the road for things like logging.

It takes a `func() tfprotov5.ProviderServer`, which it will use to
instantiate a tfprotov5.ProviderServer, which it will then serve.
Factories only this time.

Finally, I made it use the variadic options pattern so we can add more
options later and offer a clearer indication of what's required when. I
added two sample implementations of providing your own logger to
go-plugin and of using the test mode of go-plugin that allows for
reattaching to running provider processes.

Author: Paddy Carver

go.mod

@@ -4,6 +4,7 @@ go 1.14
 
 require (
 	github.com/golang/protobuf v1.4.2
+	github.com/hashicorp/go-hclog v0.0.0-20180709165350-ff2cf002a8dd
 	github.com/hashicorp/go-plugin v1.3.0
 	github.com/kr/pretty v0.1.0 // indirect
 	github.com/vmihailenco/msgpack v4.0.4+incompatible

tfprotov5/server/server.go

@@ -3,12 +3,82 @@ package tfprotov5server
 import (
 	"context"
 
+	"github.com/hashicorp/go-hclog"
+	"github.com/hashicorp/go-plugin"
 	"github.com/hashicorp/terraform-plugin-go/tfprotov5"
 	"github.com/hashicorp/terraform-plugin-go/tfprotov5/internal/fromproto"
 	"github.com/hashicorp/terraform-plugin-go/tfprotov5/internal/tfplugin5"
 	"github.com/hashicorp/terraform-plugin-go/tfprotov5/internal/toproto"
 )
 
+type ServeOpt interface {
+	ApplyServeOpt(*ServeConfig) error
+}
+
+type ServeConfig struct {
+	logger       hclog.Logger
+	debugCtx     context.Context
+	debugCh      chan *plugin.ReattachConfig
+	debugCloseCh chan struct{}
+}
+
+type serveConfigFunc func(*ServeConfig) error
+
+func (s serveConfigFunc) ApplyServeOpt(in *ServeConfig) error {
+	return s(in)
+}
+
+func WithDebug(ctx context.Context, config chan *plugin.ReattachConfig, closeCh chan struct{}) ServeOpt {
+	return serveConfigFunc(func(in *ServeConfig) error {
+		in.debugCtx = ctx
+		in.debugCh = config
+		in.debugCloseCh = closeCh
+		return nil
+	})
+}
+
+func WithGoPluginLogger(logger hclog.Logger) ServeOpt {
+	return serveConfigFunc(func(in *ServeConfig) error {
+		in.logger = logger
+		return nil
+	})
+}
+
+func Serve(name string, serverFactory func() tfprotov5.ProviderServer, opts ...ServeOpt) error {
+	var conf ServeConfig
+	for _, opt := range opts {
+		err := opt.ApplyServeOpt(&conf)
+		if err != nil {
+			return err
+		}
+	}
+	serveConfig := &plugin.ServeConfig{
+		HandshakeConfig: plugin.HandshakeConfig{
+			ProtocolVersion:  5,
+			MagicCookieKey:   "TF_PLUGIN_MAGIC_COOKIE",
+			MagicCookieValue: "d602bf8f470bc67ca7faa0386276bbdd4330efaf76d1a219cb4d6991ca9872b2",
+		},
+		Plugins: plugin.PluginSet{
+			"provider": &GRPCProviderPlugin{
+				GRPCProvider: serverFactory,
+			},
+		},
+		GRPCServer: plugin.DefaultGRPCServer,
+	}
+	if conf.logger != nil {
+		serveConfig.Logger = conf.logger
+	}
+	if conf.debugCh != nil {
+		serveConfig.Test = &plugin.ServeTestConfig{
+			Context:          conf.debugCtx,
+			ReattachConfigCh: conf.debugCh,
+			CloseCh:          conf.debugCloseCh,
+		}
+	}
+	plugin.Serve(serveConfig)
+	return nil
+}
+
 type server struct {
 	downstream tfprotov5.ProviderServer
 	tfplugin5.UnimplementedProviderServer