internal/lsp/lsprpc/lsprpc.go - tools - Git at Google

 // Copyright 2020 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 // Package lsprpc implements a jsonrpc2.StreamServer that may be used to
 // serve the LSP on a jsonrpc2 channel.
 package lsprpc

 import (
 	"context"
 	"encoding/json"
 	"fmt"
 	"log"
 	"net"
 	"os"
 	"strconv"
 	"sync/atomic"
 	"time"

 	"golang.org/x/tools/internal/event"
 	"golang.org/x/tools/internal/gocommand"
 	"golang.org/x/tools/internal/jsonrpc2"
 	"golang.org/x/tools/internal/lsp"
 	"golang.org/x/tools/internal/lsp/cache"
 	"golang.org/x/tools/internal/lsp/debug"
 	"golang.org/x/tools/internal/lsp/debug/tag"
 	"golang.org/x/tools/internal/lsp/protocol"
 	errors "golang.org/x/xerrors"
 )

 // AutoNetwork is the pseudo network type used to signal that gopls should use
 // automatic discovery to resolve a remote address.
 const AutoNetwork = "auto"

 // Unique identifiers for client/server.
 var serverIndex int64

 // The StreamServer type is a jsonrpc2.StreamServer that handles incoming
 // streams as a new LSP session, using a shared cache.
 type StreamServer struct {
 	cache *cache.Cache
 	// daemon controls whether or not to log new connections.
 	daemon bool

 	// serverForTest may be set to a test fake for testing.
 	serverForTest protocol.Server
 }

 // NewStreamServer creates a StreamServer using the shared cache. If
 // withTelemetry is true, each session is instrumented with telemetry that
 // records RPC statistics.
 func NewStreamServer(cache *cache.Cache, daemon bool) *StreamServer {
 	return &StreamServer{cache: cache, daemon: daemon}
 }

 // ServeStream implements the jsonrpc2.StreamServer interface, by handling
 // incoming streams using a new lsp server.
 func (s *StreamServer) ServeStream(ctx context.Context, conn jsonrpc2.Conn) error {
 	client := protocol.ClientDispatcher(conn)
 	session := s.cache.NewSession(ctx)
 	server := s.serverForTest
 	if server == nil {
 		server = lsp.NewServer(session, client)
 	}
 	// Clients may or may not send a shutdown message. Make sure the server is
 	// shut down.
 	// TODO(rFindley): this shutdown should perhaps be on a disconnected context.
 	defer func() {
 		if err := server.Shutdown(ctx); err != nil {
 			event.Error(ctx, "error shutting down", err)
 		}
 	}()
 	executable, err := os.Executable()
 	if err != nil {
 		log.Printf("error getting gopls path: %v", err)
 		executable = ""
 	}
 	ctx = protocol.WithClient(ctx, client)
 	conn.Go(ctx,
 		protocol.Handlers(
 			handshaker(session, executable, s.daemon,
 				protocol.ServerHandler(server,
 					jsonrpc2.MethodNotFound))))
 	if s.daemon {
 		log.Printf("Session %s: connected", session.ID())
 		defer log.Printf("Session %s: exited", session.ID())
 	}
 	<-conn.Done()
 	return conn.Err()
 }

 // A Forwarder is a jsonrpc2.StreamServer that handles an LSP stream by
 // forwarding it to a remote. This is used when the gopls process started by
 // the editor is in the `-remote` mode, which means it finds and connects to a
 // separate gopls daemon. In these cases, we still want the forwarder gopls to
 // be instrumented with telemetry, and want to be able to in some cases hijack
 // the jsonrpc2 connection with the daemon.
 type Forwarder struct {
 	network, addr string

 	// goplsPath is the path to the current executing gopls binary.
 	goplsPath string

 	// configuration for the auto-started gopls remote.
 	remoteConfig remoteConfig
 }

 type remoteConfig struct {
 	debug         string
 	listenTimeout time.Duration
 	logfile       string
 }

 // A RemoteOption configures the behavior of the auto-started remote.
 type RemoteOption interface {
 	set(*remoteConfig)
 }

 // RemoteDebugAddress configures the address used by the auto-started Gopls daemon
 // for serving debug information.
 type RemoteDebugAddress string

 func (d RemoteDebugAddress) set(cfg *remoteConfig) {
 	cfg.debug = string(d)
 }

 // RemoteListenTimeout configures the amount of time the auto-started gopls
 // daemon will wait with no client connections before shutting down.
 type RemoteListenTimeout time.Duration

 func (d RemoteListenTimeout) set(cfg *remoteConfig) {
 	cfg.listenTimeout = time.Duration(d)
 }

 // RemoteLogfile configures the logfile location for the auto-started gopls
 // daemon.
 type RemoteLogfile string

 func (l RemoteLogfile) set(cfg *remoteConfig) {
 	cfg.logfile = string(l)
 }

 func defaultRemoteConfig() remoteConfig {
 	return remoteConfig{
 		listenTimeout: 1 * time.Minute,
 	}
 }

 // NewForwarder creates a new Forwarder, ready to forward connections to the
 // remote server specified by network and addr.
 func NewForwarder(network, addr string, opts ...RemoteOption) *Forwarder {
 	gp, err := os.Executable()
 	if err != nil {
 		log.Printf("error getting gopls path for forwarder: %v", err)
 		gp = ""
 	}

 	rcfg := defaultRemoteConfig()
 	for _, opt := range opts {
 		opt.set(&rcfg)
 	}

 	fwd := &Forwarder{
 		network:      network,
 		addr:         addr,
 		goplsPath:    gp,
 		remoteConfig: rcfg,
 	}
 	return fwd
 }

 // QueryServerState queries the server state of the current server.
 func QueryServerState(ctx context.Context, network, address string) (*ServerState, error) {
 	if network == AutoNetwork {
 		gp, err := os.Executable()
 		if err != nil {
 			return nil, errors.Errorf("getting gopls path: %w", err)
 		}
 		network, address = autoNetworkAddress(gp, address)
 	}
 	netConn, err := net.DialTimeout(network, address, 5*time.Second)
 	if err != nil {
 		return nil, errors.Errorf("dialing remote: %w", err)
 	}
 	serverConn := jsonrpc2.NewConn(jsonrpc2.NewHeaderStream(netConn))
 	serverConn.Go(ctx, jsonrpc2.MethodNotFound)
 	var state ServerState
 	if err := protocol.Call(ctx, serverConn, sessionsMethod, nil, &state); err != nil {
 		return nil, errors.Errorf("querying server state: %w", err)
 	}
 	return &state, nil
 }

 // ServeStream dials the forwarder remote and binds the remote to serve the LSP
 // on the incoming stream.
 func (f *Forwarder) ServeStream(ctx context.Context, clientConn jsonrpc2.Conn) error {
 	client := protocol.ClientDispatcher(clientConn)

 	netConn, err := f.connectToRemote(ctx)
 	if err != nil {
 		return errors.Errorf("forwarder: connecting to remote: %w", err)
 	}
 	serverConn := jsonrpc2.NewConn(jsonrpc2.NewHeaderStream(netConn))
 	server := protocol.ServerDispatcher(serverConn)

 	// Forward between connections.
 	serverConn.Go(ctx,
 		protocol.Handlers(
 			protocol.ClientHandler(client,
 				jsonrpc2.MethodNotFound)))
 	// Don't run the clientConn yet, so that we can complete the handshake before
 	// processing any client messages.

 	// Do a handshake with the server instance to exchange debug information.
 	index := atomic.AddInt64(&serverIndex, 1)
 	serverID := strconv.FormatInt(index, 10)
 	var (
 		hreq = handshakeRequest{
 			ServerID:  serverID,
 			GoplsPath: f.goplsPath,
 		}
 		hresp handshakeResponse
 	)
 	if di := debug.GetInstance(ctx); di != nil {
 		hreq.Logfile = di.Logfile
 		hreq.DebugAddr = di.ListenedDebugAddress
 	}
 	if err := protocol.Call(ctx, serverConn, handshakeMethod, hreq, &hresp); err != nil {
 		// TODO(rfindley): at some point in the future we should return an error
 		// here.  Handshakes have become functional in nature.
 		event.Error(ctx, "forwarder: gopls handshake failed", err)
 	}
 	if hresp.GoplsPath != f.goplsPath {
 		event.Error(ctx, "", fmt.Errorf("forwarder: gopls path mismatch: forwarder is %q, remote is %q", f.goplsPath, hresp.GoplsPath))
 	}
 	event.Log(ctx, "New server",
 		tag.NewServer.Of(serverID),
 		tag.Logfile.Of(hresp.Logfile),
 		tag.DebugAddress.Of(hresp.DebugAddr),
 		tag.GoplsPath.Of(hresp.GoplsPath),
 		tag.ClientID.Of(hresp.SessionID),
 	)
 	clientConn.Go(ctx,
 		protocol.Handlers(
 			forwarderHandler(
 				protocol.ServerHandler(server,
 					jsonrpc2.MethodNotFound))))

 	select {
 	case <-serverConn.Done():
 		clientConn.Close()
 	case <-clientConn.Done():
 		serverConn.Close()
 	}

 	err = nil
 	if serverConn.Err() != nil {
 		err = errors.Errorf("remote disconnected: %v", err)
 	} else if clientConn.Err() != nil {
 		err = errors.Errorf("client disconnected: %v", err)
 	}
 	event.Log(ctx, fmt.Sprintf("forwarder: exited with error: %v", err))
 	return err
 }

 func (f *Forwarder) connectToRemote(ctx context.Context) (net.Conn, error) {
 	return connectToRemote(ctx, f.network, f.addr, f.goplsPath, f.remoteConfig)
 }

 func ConnectToRemote(ctx context.Context, network, addr string, opts ...RemoteOption) (net.Conn, error) {
 	rcfg := defaultRemoteConfig()
 	for _, opt := range opts {
 		opt.set(&rcfg)
 	}
 	// This is not strictly necessary, as it won't be used if not connecting to
 	// the 'auto' remote.
 	goplsPath, err := os.Executable()
 	if err != nil {
 		return nil, fmt.Errorf("unable to resolve gopls path: %v", err)
 	}
 	return connectToRemote(ctx, network, addr, goplsPath, rcfg)
 }

 func connectToRemote(ctx context.Context, inNetwork, inAddr, goplsPath string, rcfg remoteConfig) (net.Conn, error) {
 	var (
 		netConn          net.Conn
 		err              error
 		network, address = inNetwork, inAddr
 	)
 	if inNetwork == AutoNetwork {
 		// f.network is overloaded to support a concept of 'automatic' addresses,
 		// which signals that the gopls remote address should be automatically
 		// derived.
 		// So we need to resolve a real network and address here.
 		network, address = autoNetworkAddress(goplsPath, inAddr)
 	}
 	// Attempt to verify that we own the remote. This is imperfect, but if we can
 	// determine that the remote is owned by a different user, we should fail.
 	ok, err := verifyRemoteOwnership(network, address)
 	if err != nil {
 		// If the ownership check itself failed, we fail open but log an error to
 		// the user.
 		event.Error(ctx, "unable to check daemon socket owner, failing open", err)
 	} else if !ok {
 		// We succesfully checked that the socket is not owned by us, we fail
 		// closed.
 		return nil, fmt.Errorf("socket %q is owned by a different user", address)
 	}
 	const dialTimeout = 1 * time.Second
 	// Try dialing our remote once, in case it is already running.
 	netConn, err = net.DialTimeout(network, address, dialTimeout)
 	if err == nil {
 		return netConn, nil
 	}
 	// If our remote is on the 'auto' network, start it if it doesn't exist.
 	if inNetwork == AutoNetwork {
 		if goplsPath == "" {
 			return nil, fmt.Errorf("cannot auto-start remote: gopls path is unknown")
 		}
 		if network == "unix" {
 			// Sometimes the socketfile isn't properly cleaned up when gopls shuts
 			// down. Since we have already tried and failed to dial this address, it
 			// should *usually* be safe to remove the socket before binding to the
 			// address.
 			// TODO(rfindley): there is probably a race here if multiple gopls
 			// instances are simultaneously starting up.
 			if _, err := os.Stat(address); err == nil {
 				if err := os.Remove(address); err != nil {
 					return nil, errors.Errorf("removing remote socket file: %w", err)
 				}
 			}
 		}
 		args := []string{"serve",
 			"-listen", fmt.Sprintf(`%s;%s`, network, address),
 			"-listen.timeout", rcfg.listenTimeout.String(),
 		}
 		if rcfg.logfile != "" {
 			args = append(args, "-logfile", rcfg.logfile)
 		}
 		if rcfg.debug != "" {
 			args = append(args, "-debug", rcfg.debug)
 		}
 		if err := startRemote(goplsPath, args...); err != nil {
 			return nil, errors.Errorf("startRemote(%q, %v): %w", goplsPath, args, err)
 		}
 	}

 	const retries = 5
 	// It can take some time for the newly started server to bind to our address,
 	// so we retry for a bit.
 	for retry := 0; retry < retries; retry++ {
 		startDial := time.Now()
 		netConn, err = net.DialTimeout(network, address, dialTimeout)
 		if err == nil {
 			return netConn, nil
 		}
 		event.Log(ctx, fmt.Sprintf("failed attempt #%d to connect to remote: %v\n", retry+2, err))
 		// In case our failure was a fast-failure, ensure we wait at least
 		// f.dialTimeout before trying again.
 		if retry != retries-1 {
 			time.Sleep(dialTimeout - time.Since(startDial))
 		}
 	}
 	return nil, errors.Errorf("dialing remote: %w", err)
 }

 // forwarderHandler intercepts 'exit' messages to prevent the shared gopls
 // instance from exiting. In the future it may also intercept 'shutdown' to
 // provide more graceful shutdown of the client connection.
 func forwarderHandler(handler jsonrpc2.Handler) jsonrpc2.Handler {
 	return func(ctx context.Context, reply jsonrpc2.Replier, r jsonrpc2.Request) error {
 		// The gopls workspace environment defaults to the process environment in
 		// which gopls daemon was started. To avoid discrepancies in Go environment
 		// between the editor and daemon, inject any unset variables in `go env`
 		// into the options sent by initialize.
 		//
 		// See also golang.org/issue/37830.
 		if r.Method() == "initialize" {
 			if newr, err := addGoEnvToInitializeRequest(ctx, r); err == nil {
 				r = newr
 			} else {
 				log.Printf("unable to add local env to initialize request: %v", err)
 			}
 		}
 		return handler(ctx, reply, r)
 	}
 }

 // addGoEnvToInitializeRequest builds a new initialize request in which we set
 // any environment variables output by `go env` and not already present in the
 // request.
 //
 // It returns an error if r is not an initialize requst, or is otherwise
 // malformed.
 func addGoEnvToInitializeRequest(ctx context.Context, r jsonrpc2.Request) (jsonrpc2.Request, error) {
 	var params protocol.ParamInitialize
 	if err := json.Unmarshal(r.Params(), &params); err != nil {
 		return nil, err
 	}
 	var opts map[string]interface{}
 	switch v := params.InitializationOptions.(type) {
 	case nil:
 		opts = make(map[string]interface{})
 	case map[string]interface{}:
 		opts = v
 	default:
 		return nil, fmt.Errorf("unexpected type for InitializationOptions: %T", v)
 	}
 	envOpt, ok := opts["env"]
 	if !ok {
 		envOpt = make(map[string]interface{})
 	}
 	env, ok := envOpt.(map[string]interface{})
 	if !ok {
 		return nil, fmt.Errorf(`env option is %T, expected a map`, envOpt)
 	}
 	goenv, err := getGoEnv(ctx, env)
 	if err != nil {
 		return nil, err
 	}
 	for govar, value := range goenv {
 		env[govar] = value
 	}
 	opts["env"] = env
 	params.InitializationOptions = opts
 	call, ok := r.(*jsonrpc2.Call)
 	if !ok {
 		return nil, fmt.Errorf("%T is not a *jsonrpc2.Call", r)
 	}
 	return jsonrpc2.NewCall(call.ID(), "initialize", params)
 }

 func getGoEnv(ctx context.Context, env map[string]interface{}) (map[string]string, error) {
 	var runEnv []string
 	for k, v := range env {
 		runEnv = append(runEnv, fmt.Sprintf("%s=%s", k, v))
 	}
 	runner := gocommand.Runner{}
 	output, err := runner.Run(ctx, gocommand.Invocation{
 		Verb: "env",
 		Args: []string{"-json"},
 		Env:  runEnv,
 	})
 	if err != nil {
 		return nil, err
 	}
 	envmap := make(map[string]string)
 	if err := json.Unmarshal(output.Bytes(), &envmap); err != nil {
 		return nil, err
 	}
 	return envmap, nil
 }

 // A handshakeRequest identifies a client to the LSP server.
 type handshakeRequest struct {
 	// ServerID is the ID of the server on the client. This should usually be 0.
 	ServerID string `json:"serverID"`
 	// Logfile is the location of the clients log file.
 	Logfile string `json:"logfile"`
 	// DebugAddr is the client debug address.
 	DebugAddr string `json:"debugAddr"`
 	// GoplsPath is the path to the Gopls binary running the current client
 	// process.
 	GoplsPath string `json:"goplsPath"`
 }

 // A handshakeResponse is returned by the LSP server to tell the LSP client
 // information about its session.
 type handshakeResponse struct {
 	// SessionID is the server session associated with the client.
 	SessionID string `json:"sessionID"`
 	// Logfile is the location of the server logs.
 	Logfile string `json:"logfile"`
 	// DebugAddr is the server debug address.
 	DebugAddr string `json:"debugAddr"`
 	// GoplsPath is the path to the Gopls binary running the current server
 	// process.
 	GoplsPath string `json:"goplsPath"`
 }

 // ClientSession identifies a current client LSP session on the server. Note
 // that it looks similar to handshakeResposne, but in fact 'Logfile' and
 // 'DebugAddr' now refer to the client.
 type ClientSession struct {
 	SessionID string `json:"sessionID"`
 	Logfile   string `json:"logfile"`
 	DebugAddr string `json:"debugAddr"`
 }

 // ServerState holds information about the gopls daemon process, including its
 // debug information and debug information of all of its current connected
 // clients.
 type ServerState struct {
 	Logfile         string          `json:"logfile"`
 	DebugAddr       string          `json:"debugAddr"`
 	GoplsPath       string          `json:"goplsPath"`
 	CurrentClientID string          `json:"currentClientID"`
 	Clients         []ClientSession `json:"clients"`
 }

 const (
 	handshakeMethod = "gopls/handshake"
 	sessionsMethod  = "gopls/sessions"
 )

 func handshaker(session *cache.Session, goplsPath string, logHandshakes bool, handler jsonrpc2.Handler) jsonrpc2.Handler {
 	return func(ctx context.Context, reply jsonrpc2.Replier, r jsonrpc2.Request) error {
 		switch r.Method() {
 		case handshakeMethod:
 			// We log.Printf in this handler, rather than event.Log when we want logs
 			// to go to the daemon log rather than being reflected back to the
 			// client.
 			var req handshakeRequest
 			if err := json.Unmarshal(r.Params(), &req); err != nil {
 				if logHandshakes {
 					log.Printf("Error processing handshake for session %s: %v", session.ID(), err)
 				}
 				sendError(ctx, reply, err)
 				return nil
 			}
 			if logHandshakes {
 				log.Printf("Session %s: got handshake. Logfile: %q, Debug addr: %q", session.ID(), req.Logfile, req.DebugAddr)
 			}
 			event.Log(ctx, "Handshake session update",
 				cache.KeyUpdateSession.Of(session),
 				tag.DebugAddress.Of(req.DebugAddr),
 				tag.Logfile.Of(req.Logfile),
 				tag.ServerID.Of(req.ServerID),
 				tag.GoplsPath.Of(req.GoplsPath),
 			)
 			resp := handshakeResponse{
 				SessionID: session.ID(),
 				GoplsPath: goplsPath,
 			}
 			if di := debug.GetInstance(ctx); di != nil {
 				resp.Logfile = di.Logfile
 				resp.DebugAddr = di.ListenedDebugAddress
 			}

 			return reply(ctx, resp, nil)
 		case sessionsMethod:
 			resp := ServerState{
 				GoplsPath:       goplsPath,
 				CurrentClientID: session.ID(),
 			}
 			if di := debug.GetInstance(ctx); di != nil {
 				resp.Logfile = di.Logfile
 				resp.DebugAddr = di.ListenedDebugAddress
 				for _, c := range di.State.Clients() {
 					resp.Clients = append(resp.Clients, ClientSession{
 						SessionID: c.Session.ID(),
 						Logfile:   c.Logfile,
 						DebugAddr: c.DebugAddress,
 					})
 				}
 			}
 			return reply(ctx, resp, nil)
 		}
 		return handler(ctx, reply, r)
 	}
 }

 func sendError(ctx context.Context, reply jsonrpc2.Replier, err error) {
 	err = errors.Errorf("%v: %w", err, jsonrpc2.ErrParse)
 	if err := reply(ctx, nil, err); err != nil {
 		event.Error(ctx, "", err)
 	}
 }
	// Copyright 2020 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	// Package lsprpc implements a jsonrpc2.StreamServer that may be used to
	// serve the LSP on a jsonrpc2 channel.
	package lsprpc

	import (
	"context"
	"encoding/json"
	"fmt"
	"log"
	"net"
	"os"
	"strconv"
	"sync/atomic"
	"time"

	"golang.org/x/tools/internal/event"
	"golang.org/x/tools/internal/gocommand"
	"golang.org/x/tools/internal/jsonrpc2"
	"golang.org/x/tools/internal/lsp"
	"golang.org/x/tools/internal/lsp/cache"
	"golang.org/x/tools/internal/lsp/debug"
	"golang.org/x/tools/internal/lsp/debug/tag"
	"golang.org/x/tools/internal/lsp/protocol"
	errors "golang.org/x/xerrors"
	)

	// AutoNetwork is the pseudo network type used to signal that gopls should use
	// automatic discovery to resolve a remote address.
	const AutoNetwork = "auto"

	// Unique identifiers for client/server.
	var serverIndex int64

	// The StreamServer type is a jsonrpc2.StreamServer that handles incoming
	// streams as a new LSP session, using a shared cache.
	type StreamServer struct {
	cache *cache.Cache
	// daemon controls whether or not to log new connections.
	daemon bool

	// serverForTest may be set to a test fake for testing.
	serverForTest protocol.Server
	}

	// NewStreamServer creates a StreamServer using the shared cache. If
	// withTelemetry is true, each session is instrumented with telemetry that
	// records RPC statistics.
	func NewStreamServer(cache cache.Cache, daemon bool) StreamServer {
	return &StreamServer{cache: cache, daemon: daemon}
	}

	// ServeStream implements the jsonrpc2.StreamServer interface, by handling
	// incoming streams using a new lsp server.
	func (s *StreamServer) ServeStream(ctx context.Context, conn jsonrpc2.Conn) error {
	client := protocol.ClientDispatcher(conn)
	session := s.cache.NewSession(ctx)
	server := s.serverForTest
	if server == nil {
	server = lsp.NewServer(session, client)
	}
	// Clients may or may not send a shutdown message. Make sure the server is
	// shut down.
	// TODO(rFindley): this shutdown should perhaps be on a disconnected context.
	defer func() {
	if err := server.Shutdown(ctx); err != nil {
	event.Error(ctx, "error shutting down", err)
	}
	}()
	executable, err := os.Executable()
	if err != nil {
	log.Printf("error getting gopls path: %v", err)
	executable = ""
	}
	ctx = protocol.WithClient(ctx, client)
	conn.Go(ctx,
	protocol.Handlers(
	handshaker(session, executable, s.daemon,
	protocol.ServerHandler(server,
	jsonrpc2.MethodNotFound))))
	if s.daemon {
	log.Printf("Session %s: connected", session.ID())
	defer log.Printf("Session %s: exited", session.ID())
	}
	<-conn.Done()
	return conn.Err()
	}

	// A Forwarder is a jsonrpc2.StreamServer that handles an LSP stream by
	// forwarding it to a remote. This is used when the gopls process started by
	// the editor is in the `-remote` mode, which means it finds and connects to a
	// separate gopls daemon. In these cases, we still want the forwarder gopls to
	// be instrumented with telemetry, and want to be able to in some cases hijack
	// the jsonrpc2 connection with the daemon.
	type Forwarder struct {
	network, addr string

	// goplsPath is the path to the current executing gopls binary.
	goplsPath string

	// configuration for the auto-started gopls remote.
	remoteConfig remoteConfig
	}

	type remoteConfig struct {
	debug string
	listenTimeout time.Duration
	logfile string
	}

	// A RemoteOption configures the behavior of the auto-started remote.
	type RemoteOption interface {
	set(*remoteConfig)
	}

	// RemoteDebugAddress configures the address used by the auto-started Gopls daemon
	// for serving debug information.
	type RemoteDebugAddress string

	func (d RemoteDebugAddress) set(cfg *remoteConfig) {
	cfg.debug = string(d)
	}

	// RemoteListenTimeout configures the amount of time the auto-started gopls
	// daemon will wait with no client connections before shutting down.
	type RemoteListenTimeout time.Duration

	func (d RemoteListenTimeout) set(cfg *remoteConfig) {
	cfg.listenTimeout = time.Duration(d)
	}

	// RemoteLogfile configures the logfile location for the auto-started gopls
	// daemon.
	type RemoteLogfile string

	func (l RemoteLogfile) set(cfg *remoteConfig) {
	cfg.logfile = string(l)
	}

	func defaultRemoteConfig() remoteConfig {
	return remoteConfig{
	listenTimeout: 1 * time.Minute,
	}
	}

	// NewForwarder creates a new Forwarder, ready to forward connections to the
	// remote server specified by network and addr.
	func NewForwarder(network, addr string, opts ...RemoteOption) *Forwarder {
	gp, err := os.Executable()
	if err != nil {
	log.Printf("error getting gopls path for forwarder: %v", err)
	gp = ""
	}

	rcfg := defaultRemoteConfig()
	for _, opt := range opts {
	opt.set(&rcfg)
	}

	fwd := &Forwarder{
	network: network,
	addr: addr,
	goplsPath: gp,
	remoteConfig: rcfg,
	}
	return fwd
	}

	// QueryServerState queries the server state of the current server.
	func QueryServerState(ctx context.Context, network, address string) (*ServerState, error) {
	if network == AutoNetwork {
	gp, err := os.Executable()
	if err != nil {
	return nil, errors.Errorf("getting gopls path: %w", err)
	}
	network, address = autoNetworkAddress(gp, address)
	}
	netConn, err := net.DialTimeout(network, address, 5*time.Second)
	if err != nil {
	return nil, errors.Errorf("dialing remote: %w", err)
	}
	serverConn := jsonrpc2.NewConn(jsonrpc2.NewHeaderStream(netConn))
	serverConn.Go(ctx, jsonrpc2.MethodNotFound)
	var state ServerState
	if err := protocol.Call(ctx, serverConn, sessionsMethod, nil, &state); err != nil {
	return nil, errors.Errorf("querying server state: %w", err)
	}
	return &state, nil
	}

	// ServeStream dials the forwarder remote and binds the remote to serve the LSP
	// on the incoming stream.
	func (f *Forwarder) ServeStream(ctx context.Context, clientConn jsonrpc2.Conn) error {
	client := protocol.ClientDispatcher(clientConn)

	netConn, err := f.connectToRemote(ctx)
	if err != nil {
	return errors.Errorf("forwarder: connecting to remote: %w", err)
	}
	serverConn := jsonrpc2.NewConn(jsonrpc2.NewHeaderStream(netConn))
	server := protocol.ServerDispatcher(serverConn)

	// Forward between connections.
	serverConn.Go(ctx,
	protocol.Handlers(
	protocol.ClientHandler(client,
	jsonrpc2.MethodNotFound)))
	// Don't run the clientConn yet, so that we can complete the handshake before
	// processing any client messages.

	// Do a handshake with the server instance to exchange debug information.
	index := atomic.AddInt64(&serverIndex, 1)
	serverID := strconv.FormatInt(index, 10)
	var (
	hreq = handshakeRequest{
	ServerID: serverID,
	GoplsPath: f.goplsPath,
	}
	hresp handshakeResponse
	)
	if di := debug.GetInstance(ctx); di != nil {
	hreq.Logfile = di.Logfile
	hreq.DebugAddr = di.ListenedDebugAddress
	}
	if err := protocol.Call(ctx, serverConn, handshakeMethod, hreq, &hresp); err != nil {
	// TODO(rfindley): at some point in the future we should return an error
	// here. Handshakes have become functional in nature.
	event.Error(ctx, "forwarder: gopls handshake failed", err)
	}
	if hresp.GoplsPath != f.goplsPath {
	event.Error(ctx, "", fmt.Errorf("forwarder: gopls path mismatch: forwarder is %q, remote is %q", f.goplsPath, hresp.GoplsPath))
	}
	event.Log(ctx, "New server",
	tag.NewServer.Of(serverID),
	tag.Logfile.Of(hresp.Logfile),
	tag.DebugAddress.Of(hresp.DebugAddr),
	tag.GoplsPath.Of(hresp.GoplsPath),
	tag.ClientID.Of(hresp.SessionID),
	)
	clientConn.Go(ctx,
	protocol.Handlers(
	forwarderHandler(
	protocol.ServerHandler(server,
	jsonrpc2.MethodNotFound))))

	select {
	case <-serverConn.Done():
	clientConn.Close()
	case <-clientConn.Done():
	serverConn.Close()
	}

	err = nil
	if serverConn.Err() != nil {
	err = errors.Errorf("remote disconnected: %v", err)
	} else if clientConn.Err() != nil {
	err = errors.Errorf("client disconnected: %v", err)
	}
	event.Log(ctx, fmt.Sprintf("forwarder: exited with error: %v", err))
	return err
	}

	func (f *Forwarder) connectToRemote(ctx context.Context) (net.Conn, error) {
	return connectToRemote(ctx, f.network, f.addr, f.goplsPath, f.remoteConfig)
	}

	func ConnectToRemote(ctx context.Context, network, addr string, opts ...RemoteOption) (net.Conn, error) {
	rcfg := defaultRemoteConfig()
	for _, opt := range opts {
	opt.set(&rcfg)
	}
	// This is not strictly necessary, as it won't be used if not connecting to
	// the 'auto' remote.
	goplsPath, err := os.Executable()
	if err != nil {
	return nil, fmt.Errorf("unable to resolve gopls path: %v", err)
	}
	return connectToRemote(ctx, network, addr, goplsPath, rcfg)
	}

	func connectToRemote(ctx context.Context, inNetwork, inAddr, goplsPath string, rcfg remoteConfig) (net.Conn, error) {
	var (
	netConn net.Conn
	err error
	network, address = inNetwork, inAddr
	)
	if inNetwork == AutoNetwork {
	// f.network is overloaded to support a concept of 'automatic' addresses,
	// which signals that the gopls remote address should be automatically
	// derived.
	// So we need to resolve a real network and address here.
	network, address = autoNetworkAddress(goplsPath, inAddr)
	}
	// Attempt to verify that we own the remote. This is imperfect, but if we can
	// determine that the remote is owned by a different user, we should fail.
	ok, err := verifyRemoteOwnership(network, address)
	if err != nil {
	// If the ownership check itself failed, we fail open but log an error to
	// the user.
	event.Error(ctx, "unable to check daemon socket owner, failing open", err)
	} else if !ok {
	// We succesfully checked that the socket is not owned by us, we fail
	// closed.
	return nil, fmt.Errorf("socket %q is owned by a different user", address)
	}
	const dialTimeout = 1 * time.Second
	// Try dialing our remote once, in case it is already running.
	netConn, err = net.DialTimeout(network, address, dialTimeout)
	if err == nil {
	return netConn, nil
	}
	// If our remote is on the 'auto' network, start it if it doesn't exist.
	if inNetwork == AutoNetwork {
	if goplsPath == "" {
	return nil, fmt.Errorf("cannot auto-start remote: gopls path is unknown")
	}
	if network == "unix" {
	// Sometimes the socketfile isn't properly cleaned up when gopls shuts
	// down. Since we have already tried and failed to dial this address, it
	// should usually be safe to remove the socket before binding to the
	// address.
	// TODO(rfindley): there is probably a race here if multiple gopls
	// instances are simultaneously starting up.
	if _, err := os.Stat(address); err == nil {
	if err := os.Remove(address); err != nil {
	return nil, errors.Errorf("removing remote socket file: %w", err)
	}
	}
	}
	args := []string{"serve",
	"-listen", fmt.Sprintf(`%s;%s`, network, address),
	"-listen.timeout", rcfg.listenTimeout.String(),
	}
	if rcfg.logfile != "" {
	args = append(args, "-logfile", rcfg.logfile)
	}
	if rcfg.debug != "" {
	args = append(args, "-debug", rcfg.debug)
	}
	if err := startRemote(goplsPath, args...); err != nil {
	return nil, errors.Errorf("startRemote(%q, %v): %w", goplsPath, args, err)
	}
	}

	const retries = 5
	// It can take some time for the newly started server to bind to our address,
	// so we retry for a bit.
	for retry := 0; retry < retries; retry++ {
	startDial := time.Now()
	netConn, err = net.DialTimeout(network, address, dialTimeout)
	if err == nil {
	return netConn, nil
	}
	event.Log(ctx, fmt.Sprintf("failed attempt #%d to connect to remote: %v\n", retry+2, err))
	// In case our failure was a fast-failure, ensure we wait at least
	// f.dialTimeout before trying again.
	if retry != retries-1 {
	time.Sleep(dialTimeout - time.Since(startDial))
	}
	}
	return nil, errors.Errorf("dialing remote: %w", err)
	}

	// forwarderHandler intercepts 'exit' messages to prevent the shared gopls
	// instance from exiting. In the future it may also intercept 'shutdown' to
	// provide more graceful shutdown of the client connection.
	func forwarderHandler(handler jsonrpc2.Handler) jsonrpc2.Handler {
	return func(ctx context.Context, reply jsonrpc2.Replier, r jsonrpc2.Request) error {
	// The gopls workspace environment defaults to the process environment in
	// which gopls daemon was started. To avoid discrepancies in Go environment
	// between the editor and daemon, inject any unset variables in `go env`
	// into the options sent by initialize.
	//
	// See also golang.org/issue/37830.
	if r.Method() == "initialize" {
	if newr, err := addGoEnvToInitializeRequest(ctx, r); err == nil {
	r = newr
	} else {
	log.Printf("unable to add local env to initialize request: %v", err)
	}
	}
	return handler(ctx, reply, r)
	}
	}

	// addGoEnvToInitializeRequest builds a new initialize request in which we set
	// any environment variables output by `go env` and not already present in the
	// request.
	//
	// It returns an error if r is not an initialize requst, or is otherwise
	// malformed.
	func addGoEnvToInitializeRequest(ctx context.Context, r jsonrpc2.Request) (jsonrpc2.Request, error) {
	var params protocol.ParamInitialize
	if err := json.Unmarshal(r.Params(), &params); err != nil {
	return nil, err
	}
	var opts map[string]interface{}
	switch v := params.InitializationOptions.(type) {
	case nil:
	opts = make(map[string]interface{})
	case map[string]interface{}:
	opts = v
	default:
	return nil, fmt.Errorf("unexpected type for InitializationOptions: %T", v)
	}
	envOpt, ok := opts["env"]
	if !ok {
	envOpt = make(map[string]interface{})
	}
	env, ok := envOpt.(map[string]interface{})
	if !ok {
	return nil, fmt.Errorf(`env option is %T, expected a map`, envOpt)
	}
	goenv, err := getGoEnv(ctx, env)
	if err != nil {
	return nil, err
	}
	for govar, value := range goenv {
	env[govar] = value
	}
	opts["env"] = env
	params.InitializationOptions = opts
	call, ok := r.(*jsonrpc2.Call)
	if !ok {
	return nil, fmt.Errorf("%T is not a *jsonrpc2.Call", r)
	}
	return jsonrpc2.NewCall(call.ID(), "initialize", params)
	}

	func getGoEnv(ctx context.Context, env map[string]interface{}) (map[string]string, error) {
	var runEnv []string
	for k, v := range env {
	runEnv = append(runEnv, fmt.Sprintf("%s=%s", k, v))
	}
	runner := gocommand.Runner{}
	output, err := runner.Run(ctx, gocommand.Invocation{
	Verb: "env",
	Args: []string{"-json"},
	Env: runEnv,
	})
	if err != nil {
	return nil, err
	}
	envmap := make(map[string]string)
	if err := json.Unmarshal(output.Bytes(), &envmap); err != nil {
	return nil, err
	}
	return envmap, nil
	}

	// A handshakeRequest identifies a client to the LSP server.
	type handshakeRequest struct {
	// ServerID is the ID of the server on the client. This should usually be 0.
	ServerID string `json:"serverID"`
	// Logfile is the location of the clients log file.
	Logfile string `json:"logfile"`
	// DebugAddr is the client debug address.
	DebugAddr string `json:"debugAddr"`
	// GoplsPath is the path to the Gopls binary running the current client
	// process.
	GoplsPath string `json:"goplsPath"`
	}

	// A handshakeResponse is returned by the LSP server to tell the LSP client
	// information about its session.
	type handshakeResponse struct {
	// SessionID is the server session associated with the client.
	SessionID string `json:"sessionID"`
	// Logfile is the location of the server logs.
	Logfile string `json:"logfile"`
	// DebugAddr is the server debug address.
	DebugAddr string `json:"debugAddr"`
	// GoplsPath is the path to the Gopls binary running the current server
	// process.
	GoplsPath string `json:"goplsPath"`
	}

	// ClientSession identifies a current client LSP session on the server. Note
	// that it looks similar to handshakeResposne, but in fact 'Logfile' and
	// 'DebugAddr' now refer to the client.
	type ClientSession struct {
	SessionID string `json:"sessionID"`
	Logfile string `json:"logfile"`
	DebugAddr string `json:"debugAddr"`
	}

	// ServerState holds information about the gopls daemon process, including its
	// debug information and debug information of all of its current connected
	// clients.
	type ServerState struct {
	Logfile string `json:"logfile"`
	DebugAddr string `json:"debugAddr"`
	GoplsPath string `json:"goplsPath"`
	CurrentClientID string `json:"currentClientID"`
	Clients []ClientSession `json:"clients"`
	}

	const (
	handshakeMethod = "gopls/handshake"
	sessionsMethod = "gopls/sessions"
	)

	func handshaker(session *cache.Session, goplsPath string, logHandshakes bool, handler jsonrpc2.Handler) jsonrpc2.Handler {
	return func(ctx context.Context, reply jsonrpc2.Replier, r jsonrpc2.Request) error {
	switch r.Method() {
	case handshakeMethod:
	// We log.Printf in this handler, rather than event.Log when we want logs
	// to go to the daemon log rather than being reflected back to the
	// client.
	var req handshakeRequest
	if err := json.Unmarshal(r.Params(), &req); err != nil {
	if logHandshakes {
	log.Printf("Error processing handshake for session %s: %v", session.ID(), err)
	}
	sendError(ctx, reply, err)
	return nil
	}
	if logHandshakes {
	log.Printf("Session %s: got handshake. Logfile: %q, Debug addr: %q", session.ID(), req.Logfile, req.DebugAddr)
	}
	event.Log(ctx, "Handshake session update",
	cache.KeyUpdateSession.Of(session),
	tag.DebugAddress.Of(req.DebugAddr),
	tag.Logfile.Of(req.Logfile),
	tag.ServerID.Of(req.ServerID),
	tag.GoplsPath.Of(req.GoplsPath),
	)
	resp := handshakeResponse{
	SessionID: session.ID(),
	GoplsPath: goplsPath,
	}
	if di := debug.GetInstance(ctx); di != nil {
	resp.Logfile = di.Logfile
	resp.DebugAddr = di.ListenedDebugAddress
	}

	return reply(ctx, resp, nil)
	case sessionsMethod:
	resp := ServerState{
	GoplsPath: goplsPath,
	CurrentClientID: session.ID(),
	}
	if di := debug.GetInstance(ctx); di != nil {
	resp.Logfile = di.Logfile
	resp.DebugAddr = di.ListenedDebugAddress
	for _, c := range di.State.Clients() {
	resp.Clients = append(resp.Clients, ClientSession{
	SessionID: c.Session.ID(),
	Logfile: c.Logfile,
	DebugAddr: c.DebugAddress,
	})
	}
	}
	return reply(ctx, resp, nil)
	}
	return handler(ctx, reply, r)
	}
	}

	func sendError(ctx context.Context, reply jsonrpc2.Replier, err error) {
	err = errors.Errorf("%v: %w", err, jsonrpc2.ErrParse)
	if err := reply(ctx, nil, err); err != nil {
	event.Error(ctx, "", err)
	}
	}