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/sync/errgroup"
 	"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/protocol"
 	"golang.org/x/tools/internal/telemetry/event"
 )

 // 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 clientIndex, 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

 	// 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) *StreamServer {
 	return &StreamServer{cache: cache}
 }

 // debugInstance is the common functionality shared between client and server
 // gopls instances.
 type debugInstance struct {
 	id           string
 	debugAddress string
 	logfile      string
 	goplsPath    string
 }

 func (d debugInstance) ID() string {
 	return d.id
 }

 func (d debugInstance) DebugAddress() string {
 	return d.debugAddress
 }

 func (d debugInstance) Logfile() string {
 	return d.logfile
 }

 func (d debugInstance) GoplsPath() string {
 	return d.goplsPath
 }

 // A debugServer is held by the client to identity the remove server to which
 // it is connected.
 type debugServer struct {
 	debugInstance
 	// clientID is the id of this client on the server.
 	clientID string
 }

 func (s debugServer) ClientID() string {
 	return s.clientID
 }

 // A debugClient is held by the server to identify an incoming client
 // connection.
 type debugClient struct {
 	debugInstance
 	// session is the session serving this client.
 	session *cache.Session
 	// serverID is this id of this server on the client.
 	serverID string
 }

 func (c debugClient) Session() debug.Session {
 	return cache.DebugSession{Session: c.session}
 }

 func (c debugClient) ServerID() string {
 	return c.serverID
 }

 // ServeStream implements the jsonrpc2.StreamServer interface, by handling
 // incoming streams using a new lsp server.
 func (s *StreamServer) ServeStream(ctx context.Context, stream jsonrpc2.Stream) error {
 	index := atomic.AddInt64(&clientIndex, 1)

 	conn := jsonrpc2.NewConn(stream)
 	client := protocol.ClientDispatcher(conn)
 	session := s.cache.NewSession(ctx)
 	dc := &debugClient{
 		debugInstance: debugInstance{
 			id: strconv.FormatInt(index, 10),
 		},
 		session: session,
 	}
 	if di := debug.GetInstance(ctx); di != nil {
 		di.State.AddClient(dc)
 		defer di.State.DropClient(dc)
 	}
 	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)
 	return conn.Run(ctx,
 		protocol.Handlers(
 			handshaker(dc, executable,
 				protocol.ServerHandler(server,
 					jsonrpc2.MethodNotFound))))
 }

 // 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
 	dialTimeout         time.Duration
 	retries             int
 	remoteDebug         string
 	remoteListenTimeout time.Duration
 	remoteLogfile       string
 }

 // A ForwarderOption configures the behavior of the LSP forwarder.
 type ForwarderOption interface {
 	setForwarder(*Forwarder)
 }

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

 func (d RemoteDebugAddress) setForwarder(fwd *Forwarder) {
 	fwd.remoteDebug = 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) setForwarder(fwd *Forwarder) {
 	fwd.remoteListenTimeout = time.Duration(d)
 }

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

 func (l RemoteLogfile) setForwarder(fwd *Forwarder) {
 	fwd.remoteLogfile = string(l)
 }

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

 	fwd := &Forwarder{
 		network:             network,
 		addr:                addr,
 		goplsPath:           gp,
 		dialTimeout:         1 * time.Second,
 		retries:             5,
 		remoteLogfile:       "auto",
 		remoteListenTimeout: 1 * time.Minute,
 	}
 	for _, opt := range opts {
 		opt.setForwarder(fwd)
 	}
 	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, fmt.Errorf("getting gopls path: %v", err)
 		}
 		network, address = autoNetworkAddress(gp, address)
 	}
 	netConn, err := net.DialTimeout(network, address, 5*time.Second)
 	if err != nil {
 		return nil, fmt.Errorf("dialing remote: %v", err)
 	}
 	serverConn := jsonrpc2.NewConn(jsonrpc2.NewHeaderStream(netConn, netConn))
 	go serverConn.Run(ctx, jsonrpc2.MethodNotFound)
 	var state ServerState
 	if err := serverConn.Call(ctx, sessionsMethod, nil, &state); err != nil {
 		return nil, fmt.Errorf("querying server state: %v", 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, stream jsonrpc2.Stream) error {
 	clientConn := jsonrpc2.NewConn(stream)
 	client := protocol.ClientDispatcher(clientConn)

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

 	// Forward between connections.
 	g, ctx := errgroup.WithContext(ctx)
 	g.Go(func() error {
 		return serverConn.Run(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)
 	di := debug.GetInstance(ctx)
 	var (
 		hreq = handshakeRequest{
 			ServerID:  serverID,
 			GoplsPath: f.goplsPath,
 		}
 		hresp handshakeResponse
 	)
 	if di != nil {
 		hreq.Logfile = di.Logfile
 		hreq.DebugAddr = di.ListenedDebugAddress
 	}
 	if err := serverConn.Call(ctx, handshakeMethod, hreq, &hresp); err != nil {
 		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))
 	}
 	if di != nil {
 		di.State.AddServer(debugServer{
 			debugInstance: debugInstance{
 				id:           serverID,
 				logfile:      hresp.Logfile,
 				debugAddress: hresp.DebugAddr,
 				goplsPath:    hresp.GoplsPath,
 			},
 			clientID: hresp.ClientID,
 		})
 	}
 	g.Go(func() error {
 		return clientConn.Run(ctx,
 			protocol.Handlers(
 				forwarderHandler(
 					protocol.ServerHandler(server,
 						jsonrpc2.MethodNotFound))))
 	})

 	return g.Wait()
 }

 func (f *Forwarder) connectToRemote(ctx context.Context) (net.Conn, error) {
 	var (
 		netConn          net.Conn
 		err              error
 		network, address = f.network, f.addr
 	)
 	if f.network == 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(f.goplsPath, f.addr)
 	}
 	// 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: %v", 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)
 	}
 	// Try dialing our remote once, in case it is already running.
 	netConn, err = net.DialTimeout(network, address, f.dialTimeout)
 	if err == nil {
 		return netConn, nil
 	}
 	// If our remote is on the 'auto' network, start it if it doesn't exist.
 	if f.network == AutoNetwork {
 		if f.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, fmt.Errorf("removing remote socket file: %v", err)
 				}
 			}
 		}
 		args := []string{"serve",
 			"-listen", fmt.Sprintf(`%s;%s`, network, address),
 			"-listen.timeout", f.remoteListenTimeout.String(),
 			"-logfile", f.remoteLogfile,
 		}
 		if f.remoteDebug != "" {
 			args = append(args, "-debug", f.remoteDebug)
 		}
 		if err := startRemote(f.goplsPath, args...); err != nil {
 			return nil, fmt.Errorf("startRemote(%q, %v): %v", f.goplsPath, args, err)
 		}
 	}

 	// 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 < f.retries; retry++ {
 		startDial := time.Now()
 		netConn, err = net.DialTimeout(network, address, f.dialTimeout)
 		if err == nil {
 			return netConn, nil
 		}
 		event.Print(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 != f.retries-1 {
 			time.Sleep(f.dialTimeout - time.Since(startDial))
 		}
 	}
 	return nil, fmt.Errorf("dialing remote: %v", err)
 }

 // ForwarderExitFunc is used to exit the forwarder process. It is mutable for
 // testing purposes.
 var ForwarderExitFunc = os.Exit

 // OverrideExitFuncsForTest can be used from test code to prevent the test
 // process from exiting on server shutdown. The returned func reverts the exit
 // funcs to their previous state.
 func OverrideExitFuncsForTest() func() {
 	// Override functions that would shut down the test process
 	cleanup := func(lspExit, forwarderExit func(code int)) func() {
 		return func() {
 			lsp.ServerExitFunc = lspExit
 			ForwarderExitFunc = forwarderExit
 		}
 	}(lsp.ServerExitFunc, ForwarderExitFunc)
 	// It is an error for a test to shutdown a server process.
 	lsp.ServerExitFunc = func(code int) {
 		panic(fmt.Sprintf("LSP server exited with code %d", code))
 	}
 	// We don't want our forwarders to exit, but it's OK if they would have.
 	ForwarderExitFunc = func(code int) {}
 	return cleanup
 }

 // 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, r *jsonrpc2.Request) error {
 		// TODO(golang.org/issues/34111): we should more gracefully disconnect here,
 		// once that process exists.
 		if r.Method == "exit" {
 			ForwarderExitFunc(0)
 			// reply nil here to consume the message: in
 			// tests, ForwarderExitFunc may be overridden to something that doesn't
 			// exit the process.
 			return r.Reply(ctx, nil, nil)
 		}
 		return handler(ctx, r)
 	}
 }

 // 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 {
 	// ClientID is the ID of the client as seen on the server.
 	ClientID string `json:"clientID"`
 	// 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 {
 	ClientID  string `json:"clientID"`
 	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(client *debugClient, goplsPath string, handler jsonrpc2.Handler) jsonrpc2.Handler {
 	return func(ctx context.Context, r *jsonrpc2.Request) error {
 		switch r.Method {
 		case handshakeMethod:
 			var req handshakeRequest
 			if err := json.Unmarshal(*r.Params, &req); err != nil {
 				sendError(ctx, r, err)
 				return nil
 			}
 			client.debugAddress = req.DebugAddr
 			client.logfile = req.Logfile
 			client.serverID = req.ServerID
 			client.goplsPath = req.GoplsPath
 			resp := handshakeResponse{
 				ClientID:  client.id,
 				SessionID: cache.DebugSession{Session: client.session}.ID(),
 				GoplsPath: goplsPath,
 			}
 			if di := debug.GetInstance(ctx); di != nil {
 				resp.Logfile = di.Logfile
 				resp.DebugAddr = di.ListenedDebugAddress
 			}

 			return r.Reply(ctx, resp, nil)
 		case sessionsMethod:
 			resp := ServerState{
 				GoplsPath:       goplsPath,
 				CurrentClientID: client.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{
 						ClientID:  c.ID(),
 						SessionID: c.Session().ID(),
 						Logfile:   c.Logfile(),
 						DebugAddr: c.DebugAddress(),
 					})
 				}
 			}
 			return r.Reply(ctx, resp, nil)
 		}
 		return handler(ctx, r)
 	}
 }

 func sendError(ctx context.Context, req *jsonrpc2.Request, err error) {
 	if _, ok := err.(*jsonrpc2.Error); !ok {
 		err = jsonrpc2.NewErrorf(jsonrpc2.CodeParseError, "%v", err)
 	}
 	if err := req.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/sync/errgroup"
	"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/protocol"
	"golang.org/x/tools/internal/telemetry/event"
	)

	// 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 clientIndex, 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

	// 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) StreamServer {
	return &StreamServer{cache: cache}
	}

	// debugInstance is the common functionality shared between client and server
	// gopls instances.
	type debugInstance struct {
	id string
	debugAddress string
	logfile string
	goplsPath string
	}

	func (d debugInstance) ID() string {
	return d.id
	}

	func (d debugInstance) DebugAddress() string {
	return d.debugAddress
	}

	func (d debugInstance) Logfile() string {
	return d.logfile
	}

	func (d debugInstance) GoplsPath() string {
	return d.goplsPath
	}

	// A debugServer is held by the client to identity the remove server to which
	// it is connected.
	type debugServer struct {
	debugInstance
	// clientID is the id of this client on the server.
	clientID string
	}

	func (s debugServer) ClientID() string {
	return s.clientID
	}

	// A debugClient is held by the server to identify an incoming client
	// connection.
	type debugClient struct {
	debugInstance
	// session is the session serving this client.
	session *cache.Session
	// serverID is this id of this server on the client.
	serverID string
	}

	func (c debugClient) Session() debug.Session {
	return cache.DebugSession{Session: c.session}
	}

	func (c debugClient) ServerID() string {
	return c.serverID
	}

	// ServeStream implements the jsonrpc2.StreamServer interface, by handling
	// incoming streams using a new lsp server.
	func (s *StreamServer) ServeStream(ctx context.Context, stream jsonrpc2.Stream) error {
	index := atomic.AddInt64(&clientIndex, 1)

	conn := jsonrpc2.NewConn(stream)
	client := protocol.ClientDispatcher(conn)
	session := s.cache.NewSession(ctx)
	dc := &debugClient{
	debugInstance: debugInstance{
	id: strconv.FormatInt(index, 10),
	},
	session: session,
	}
	if di := debug.GetInstance(ctx); di != nil {
	di.State.AddClient(dc)
	defer di.State.DropClient(dc)
	}
	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)
	return conn.Run(ctx,
	protocol.Handlers(
	handshaker(dc, executable,
	protocol.ServerHandler(server,
	jsonrpc2.MethodNotFound))))
	}

	// 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
	dialTimeout time.Duration
	retries int
	remoteDebug string
	remoteListenTimeout time.Duration
	remoteLogfile string
	}

	// A ForwarderOption configures the behavior of the LSP forwarder.
	type ForwarderOption interface {
	setForwarder(*Forwarder)
	}

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

	func (d RemoteDebugAddress) setForwarder(fwd *Forwarder) {
	fwd.remoteDebug = 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) setForwarder(fwd *Forwarder) {
	fwd.remoteListenTimeout = time.Duration(d)
	}

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

	func (l RemoteLogfile) setForwarder(fwd *Forwarder) {
	fwd.remoteLogfile = string(l)
	}

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

	fwd := &Forwarder{
	network: network,
	addr: addr,
	goplsPath: gp,
	dialTimeout: 1 * time.Second,
	retries: 5,
	remoteLogfile: "auto",
	remoteListenTimeout: 1 * time.Minute,
	}
	for _, opt := range opts {
	opt.setForwarder(fwd)
	}
	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, fmt.Errorf("getting gopls path: %v", err)
	}
	network, address = autoNetworkAddress(gp, address)
	}
	netConn, err := net.DialTimeout(network, address, 5*time.Second)
	if err != nil {
	return nil, fmt.Errorf("dialing remote: %v", err)
	}
	serverConn := jsonrpc2.NewConn(jsonrpc2.NewHeaderStream(netConn, netConn))
	go serverConn.Run(ctx, jsonrpc2.MethodNotFound)
	var state ServerState
	if err := serverConn.Call(ctx, sessionsMethod, nil, &state); err != nil {
	return nil, fmt.Errorf("querying server state: %v", 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, stream jsonrpc2.Stream) error {
	clientConn := jsonrpc2.NewConn(stream)
	client := protocol.ClientDispatcher(clientConn)

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

	// Forward between connections.
	g, ctx := errgroup.WithContext(ctx)
	g.Go(func() error {
	return serverConn.Run(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)
	di := debug.GetInstance(ctx)
	var (
	hreq = handshakeRequest{
	ServerID: serverID,
	GoplsPath: f.goplsPath,
	}
	hresp handshakeResponse
	)
	if di != nil {
	hreq.Logfile = di.Logfile
	hreq.DebugAddr = di.ListenedDebugAddress
	}
	if err := serverConn.Call(ctx, handshakeMethod, hreq, &hresp); err != nil {
	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))
	}
	if di != nil {
	di.State.AddServer(debugServer{
	debugInstance: debugInstance{
	id: serverID,
	logfile: hresp.Logfile,
	debugAddress: hresp.DebugAddr,
	goplsPath: hresp.GoplsPath,
	},
	clientID: hresp.ClientID,
	})
	}
	g.Go(func() error {
	return clientConn.Run(ctx,
	protocol.Handlers(
	forwarderHandler(
	protocol.ServerHandler(server,
	jsonrpc2.MethodNotFound))))
	})

	return g.Wait()
	}

	func (f *Forwarder) connectToRemote(ctx context.Context) (net.Conn, error) {
	var (
	netConn net.Conn
	err error
	network, address = f.network, f.addr
	)
	if f.network == 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(f.goplsPath, f.addr)
	}
	// 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: %v", 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)
	}
	// Try dialing our remote once, in case it is already running.
	netConn, err = net.DialTimeout(network, address, f.dialTimeout)
	if err == nil {
	return netConn, nil
	}
	// If our remote is on the 'auto' network, start it if it doesn't exist.
	if f.network == AutoNetwork {
	if f.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, fmt.Errorf("removing remote socket file: %v", err)
	}
	}
	}
	args := []string{"serve",
	"-listen", fmt.Sprintf(`%s;%s`, network, address),
	"-listen.timeout", f.remoteListenTimeout.String(),
	"-logfile", f.remoteLogfile,
	}
	if f.remoteDebug != "" {
	args = append(args, "-debug", f.remoteDebug)
	}
	if err := startRemote(f.goplsPath, args...); err != nil {
	return nil, fmt.Errorf("startRemote(%q, %v): %v", f.goplsPath, args, err)
	}
	}

	// 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 < f.retries; retry++ {
	startDial := time.Now()
	netConn, err = net.DialTimeout(network, address, f.dialTimeout)
	if err == nil {
	return netConn, nil
	}
	event.Print(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 != f.retries-1 {
	time.Sleep(f.dialTimeout - time.Since(startDial))
	}
	}
	return nil, fmt.Errorf("dialing remote: %v", err)
	}

	// ForwarderExitFunc is used to exit the forwarder process. It is mutable for
	// testing purposes.
	var ForwarderExitFunc = os.Exit

	// OverrideExitFuncsForTest can be used from test code to prevent the test
	// process from exiting on server shutdown. The returned func reverts the exit
	// funcs to their previous state.
	func OverrideExitFuncsForTest() func() {
	// Override functions that would shut down the test process
	cleanup := func(lspExit, forwarderExit func(code int)) func() {
	return func() {
	lsp.ServerExitFunc = lspExit
	ForwarderExitFunc = forwarderExit
	}
	}(lsp.ServerExitFunc, ForwarderExitFunc)
	// It is an error for a test to shutdown a server process.
	lsp.ServerExitFunc = func(code int) {
	panic(fmt.Sprintf("LSP server exited with code %d", code))
	}
	// We don't want our forwarders to exit, but it's OK if they would have.
	ForwarderExitFunc = func(code int) {}
	return cleanup
	}

	// 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, r *jsonrpc2.Request) error {
	// TODO(golang.org/issues/34111): we should more gracefully disconnect here,
	// once that process exists.
	if r.Method == "exit" {
	ForwarderExitFunc(0)
	// reply nil here to consume the message: in
	// tests, ForwarderExitFunc may be overridden to something that doesn't
	// exit the process.
	return r.Reply(ctx, nil, nil)
	}
	return handler(ctx, r)
	}
	}

	// 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 {
	// ClientID is the ID of the client as seen on the server.
	ClientID string `json:"clientID"`
	// 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 {
	ClientID string `json:"clientID"`
	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(client *debugClient, goplsPath string, handler jsonrpc2.Handler) jsonrpc2.Handler {
	return func(ctx context.Context, r *jsonrpc2.Request) error {
	switch r.Method {
	case handshakeMethod:
	var req handshakeRequest
	if err := json.Unmarshal(*r.Params, &req); err != nil {
	sendError(ctx, r, err)
	return nil
	}
	client.debugAddress = req.DebugAddr
	client.logfile = req.Logfile
	client.serverID = req.ServerID
	client.goplsPath = req.GoplsPath
	resp := handshakeResponse{
	ClientID: client.id,
	SessionID: cache.DebugSession{Session: client.session}.ID(),
	GoplsPath: goplsPath,
	}
	if di := debug.GetInstance(ctx); di != nil {
	resp.Logfile = di.Logfile
	resp.DebugAddr = di.ListenedDebugAddress
	}

	return r.Reply(ctx, resp, nil)
	case sessionsMethod:
	resp := ServerState{
	GoplsPath: goplsPath,
	CurrentClientID: client.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{
	ClientID: c.ID(),
	SessionID: c.Session().ID(),
	Logfile: c.Logfile(),
	DebugAddr: c.DebugAddress(),
	})
	}
	}
	return r.Reply(ctx, resp, nil)
	}
	return handler(ctx, r)
	}
	}

	func sendError(ctx context.Context, req *jsonrpc2.Request, err error) {
	if _, ok := err.(*jsonrpc2.Error); !ok {
	err = jsonrpc2.NewErrorf(jsonrpc2.CodeParseError, "%v", err)
	}
	if err := req.Reply(ctx, nil, err); err != nil {
	event.Error(ctx, "", err)
	}
	}