internal/lsp/fake/editor.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 fake

 import (
 	"bufio"
 	"context"
 	"errors"
 	"fmt"
 	"regexp"
 	"strings"
 	"sync"

 	"golang.org/x/tools/internal/jsonrpc2"
 	"golang.org/x/tools/internal/lsp/protocol"
 )

 // Editor is a fake editor client.  It keeps track of client state and can be
 // used for writing LSP tests.
 type Editor struct {
 	Config EditorConfig

 	// server, client, and sandbox are concurrency safe and written only
 	// at construction time, so do not require synchronization.
 	server  protocol.Server
 	client  *Client
 	sandbox *Sandbox

 	// Since this editor is intended just for testing, we use very coarse
 	// locking.
 	mu sync.Mutex
 	// Editor state.
 	buffers map[string]buffer
 	// Capabilities / Options
 	serverCapabilities protocol.ServerCapabilities
 }

 type buffer struct {
 	version int
 	path    string
 	content []string
 }

 func (b buffer) text() string {
 	return strings.Join(b.content, "\n")
 }

 // EditorConfig configures the editor's LSP session. This is similar to
 // source.UserOptions, but we use a separate type here so that we expose only
 // that configuration which we support.
 //
 // The zero value for EditorConfig should correspond to its defaults.
 type EditorConfig struct {
 	Env []string

 	// CodeLens is a map defining whether codelens are enabled, keyed by the
 	// codeLens command. CodeLens which are not present in this map are left in
 	// their default state.
 	CodeLens map[string]bool

 	// SymbolMatcher is the config associated with the "symbolMatcher" gopls
 	// config option.
 	SymbolMatcher *string
 }

 // NewEditor Creates a new Editor.
 func NewEditor(ws *Sandbox, config EditorConfig) *Editor {
 	return &Editor{
 		buffers: make(map[string]buffer),
 		sandbox: ws,
 		Config:  config,
 	}
 }

 // Connect configures the editor to communicate with an LSP server on conn. It
 // is not concurrency safe, and should be called at most once, before using the
 // editor.
 //
 // It returns the editor, so that it may be called as follows:
 //   editor, err := NewEditor(s).Connect(ctx, conn)
 func (e *Editor) Connect(ctx context.Context, conn *jsonrpc2.Conn, hooks ClientHooks) (*Editor, error) {
 	e.server = protocol.ServerDispatcher(conn)
 	e.client = &Client{editor: e, hooks: hooks}
 	go conn.Run(ctx,
 		protocol.Handlers(
 			protocol.ClientHandler(e.client,
 				jsonrpc2.MethodNotFound)))
 	if err := e.initialize(ctx); err != nil {
 		return nil, err
 	}
 	e.sandbox.Workdir.AddWatcher(e.onFileChanges)
 	return e, nil
 }

 // Shutdown issues the 'shutdown' LSP notification.
 func (e *Editor) Shutdown(ctx context.Context) error {
 	if e.server != nil {
 		if err := e.server.Shutdown(ctx); err != nil {
 			return fmt.Errorf("Shutdown: %w", err)
 		}
 	}
 	return nil
 }

 // Exit issues the 'exit' LSP notification.
 func (e *Editor) Exit(ctx context.Context) error {
 	if e.server != nil {
 		// Not all LSP clients issue the exit RPC, but we do so here to ensure that
 		// we gracefully handle it on multi-session servers.
 		if err := e.server.Exit(ctx); err != nil {
 			return fmt.Errorf("Exit: %w", err)
 		}
 	}
 	return nil
 }

 // Client returns the LSP client for this editor.
 func (e *Editor) Client() *Client {
 	return e.client
 }

 func (e *Editor) configuration() map[string]interface{} {
 	config := map[string]interface{}{
 		"verboseWorkDoneProgress": true,
 	}

 	envvars := e.sandbox.GoEnv()
 	envvars = append(envvars, e.Config.Env...)
 	env := map[string]interface{}{}
 	for _, value := range envvars {
 		kv := strings.SplitN(value, "=", 2)
 		env[kv[0]] = kv[1]
 	}
 	config["env"] = env

 	if e.Config.CodeLens != nil {
 		config["codelens"] = e.Config.CodeLens
 	}

 	if e.Config.SymbolMatcher != nil {
 		config["symbolMatcher"] = *e.Config.SymbolMatcher
 	}

 	return config
 }

 func (e *Editor) initialize(ctx context.Context) error {
 	params := &protocol.ParamInitialize{}
 	params.ClientInfo.Name = "fakeclient"
 	params.ClientInfo.Version = "v1.0.0"
 	params.RootURI = e.sandbox.Workdir.RootURI()
 	params.Capabilities.Workspace.Configuration = true
 	params.Capabilities.Window.WorkDoneProgress = true
 	// TODO: set client capabilities
 	params.InitializationOptions = e.configuration()

 	params.Trace = "messages"
 	// TODO: support workspace folders.
 	if e.server != nil {
 		resp, err := e.server.Initialize(ctx, params)
 		if err != nil {
 			return fmt.Errorf("initialize: %w", err)
 		}
 		e.mu.Lock()
 		e.serverCapabilities = resp.Capabilities
 		e.mu.Unlock()

 		if err := e.server.Initialized(ctx, &protocol.InitializedParams{}); err != nil {
 			return fmt.Errorf("initialized: %w", err)
 		}
 	}
 	// TODO: await initial configuration here, or expect gopls to manage that?
 	return nil
 }

 func (e *Editor) onFileChanges(ctx context.Context, evts []FileEvent) {
 	if e.server == nil {
 		return
 	}
 	var lspevts []protocol.FileEvent
 	for _, evt := range evts {
 		lspevts = append(lspevts, evt.ProtocolEvent)
 	}
 	e.server.DidChangeWatchedFiles(ctx, &protocol.DidChangeWatchedFilesParams{
 		Changes: lspevts,
 	})
 }

 // OpenFile creates a buffer for the given workdir-relative file.
 func (e *Editor) OpenFile(ctx context.Context, path string) error {
 	content, err := e.sandbox.Workdir.ReadFile(path)
 	if err != nil {
 		return err
 	}
 	buf := newBuffer(path, content)
 	e.mu.Lock()
 	e.buffers[path] = buf
 	item := textDocumentItem(e.sandbox.Workdir, buf)
 	e.mu.Unlock()

 	if e.server != nil {
 		if err := e.server.DidOpen(ctx, &protocol.DidOpenTextDocumentParams{
 			TextDocument: item,
 		}); err != nil {
 			return fmt.Errorf("DidOpen: %w", err)
 		}
 	}
 	return nil
 }

 func newBuffer(path, content string) buffer {
 	return buffer{
 		version: 1,
 		path:    path,
 		content: strings.Split(content, "\n"),
 	}
 }

 func textDocumentItem(wd *Workdir, buf buffer) protocol.TextDocumentItem {
 	uri := wd.URI(buf.path)
 	languageID := ""
 	if strings.HasSuffix(buf.path, ".go") {
 		// TODO: what about go.mod files? What is their language ID?
 		languageID = "go"
 	}
 	return protocol.TextDocumentItem{
 		URI:        uri,
 		LanguageID: languageID,
 		Version:    float64(buf.version),
 		Text:       buf.text(),
 	}
 }

 // CreateBuffer creates a new unsaved buffer corresponding to the workdir path,
 // containing the given textual content.
 func (e *Editor) CreateBuffer(ctx context.Context, path, content string) error {
 	buf := newBuffer(path, content)
 	e.mu.Lock()
 	e.buffers[path] = buf
 	item := textDocumentItem(e.sandbox.Workdir, buf)
 	e.mu.Unlock()

 	if e.server != nil {
 		if err := e.server.DidOpen(ctx, &protocol.DidOpenTextDocumentParams{
 			TextDocument: item,
 		}); err != nil {
 			return fmt.Errorf("DidOpen: %w", err)
 		}
 	}
 	return nil
 }

 // CloseBuffer removes the current buffer (regardless of whether it is saved).
 func (e *Editor) CloseBuffer(ctx context.Context, path string) error {
 	e.mu.Lock()
 	_, ok := e.buffers[path]
 	if !ok {
 		e.mu.Unlock()
 		return ErrUnknownBuffer
 	}
 	delete(e.buffers, path)
 	e.mu.Unlock()

 	if e.server != nil {
 		if err := e.server.DidClose(ctx, &protocol.DidCloseTextDocumentParams{
 			TextDocument: e.textDocumentIdentifier(path),
 		}); err != nil {
 			return fmt.Errorf("DidClose: %w", err)
 		}
 	}
 	return nil
 }

 func (e *Editor) textDocumentIdentifier(path string) protocol.TextDocumentIdentifier {
 	return protocol.TextDocumentIdentifier{
 		URI: e.sandbox.Workdir.URI(path),
 	}
 }

 // SaveBuffer writes the content of the buffer specified by the given path to
 // the filesystem.
 func (e *Editor) SaveBuffer(ctx context.Context, path string) error {
 	if err := e.OrganizeImports(ctx, path); err != nil {
 		return fmt.Errorf("organizing imports before save: %w", err)
 	}
 	if err := e.FormatBuffer(ctx, path); err != nil {
 		return fmt.Errorf("formatting before save: %w", err)
 	}

 	e.mu.Lock()
 	buf, ok := e.buffers[path]
 	if !ok {
 		e.mu.Unlock()
 		return fmt.Errorf(fmt.Sprintf("unknown buffer: %q", path))
 	}
 	content := buf.text()
 	includeText := false
 	syncOptions, ok := e.serverCapabilities.TextDocumentSync.(protocol.TextDocumentSyncOptions)
 	if ok {
 		includeText = syncOptions.Save.IncludeText
 	}
 	e.mu.Unlock()

 	docID := e.textDocumentIdentifier(buf.path)
 	if e.server != nil {
 		if err := e.server.WillSave(ctx, &protocol.WillSaveTextDocumentParams{
 			TextDocument: docID,
 			Reason:       protocol.Manual,
 		}); err != nil {
 			return fmt.Errorf("WillSave: %w", err)
 		}
 	}
 	if err := e.sandbox.Workdir.WriteFile(ctx, path, content); err != nil {
 		return fmt.Errorf("writing %q: %w", path, err)
 	}
 	if e.server != nil {
 		params := &protocol.DidSaveTextDocumentParams{
 			TextDocument: protocol.VersionedTextDocumentIdentifier{
 				Version:                float64(buf.version),
 				TextDocumentIdentifier: docID,
 			},
 		}
 		if includeText {
 			params.Text = &content
 		}
 		if err := e.server.DidSave(ctx, params); err != nil {
 			return fmt.Errorf("DidSave: %w", err)
 		}
 	}
 	return nil
 }

 // contentPosition returns the (Line, Column) position corresponding to offset
 // in the buffer referenced by path.
 func contentPosition(content string, offset int) (Pos, error) {
 	scanner := bufio.NewScanner(strings.NewReader(content))
 	start := 0
 	line := 0
 	for scanner.Scan() {
 		end := start + len([]rune(scanner.Text())) + 1
 		if offset < end {
 			return Pos{Line: line, Column: offset - start}, nil
 		}
 		start = end
 		line++
 	}
 	if err := scanner.Err(); err != nil {
 		return Pos{}, fmt.Errorf("scanning content: %w", err)
 	}
 	// Scan() will drop the last line if it is empty. Correct for this.
 	if strings.HasSuffix(content, "\n") && offset == start {
 		return Pos{Line: line, Column: 0}, nil
 	}
 	return Pos{}, fmt.Errorf("position %d out of bounds in %q (line = %d, start = %d)", offset, content, line, start)
 }

 // ErrNoMatch is returned if a regexp search fails.
 var (
 	ErrNoMatch       = errors.New("no match")
 	ErrUnknownBuffer = errors.New("unknown buffer")
 )

 // regexpRange returns the start and end of the first occurrence of either re
 // or its singular subgroup. It returns ErrNoMatch if the regexp doesn't match.
 func regexpRange(content, re string) (Pos, Pos, error) {
 	var start, end int
 	rec, err := regexp.Compile(re)
 	if err != nil {
 		return Pos{}, Pos{}, err
 	}
 	indexes := rec.FindStringSubmatchIndex(content)
 	if indexes == nil {
 		return Pos{}, Pos{}, ErrNoMatch
 	}
 	switch len(indexes) {
 	case 2:
 		// no subgroups: return the range of the regexp expression
 		start, end = indexes[0], indexes[1]
 	case 4:
 		// one subgroup: return its range
 		start, end = indexes[2], indexes[3]
 	default:
 		return Pos{}, Pos{}, fmt.Errorf("invalid search regexp %q: expect either 0 or 1 subgroups, got %d", re, len(indexes)/2-1)
 	}
 	startPos, err := contentPosition(content, start)
 	if err != nil {
 		return Pos{}, Pos{}, err
 	}
 	endPos, err := contentPosition(content, end)
 	if err != nil {
 		return Pos{}, Pos{}, err
 	}
 	return startPos, endPos, nil
 }

 // RegexpSearch returns the position of the first match for re in the buffer
 // bufName. For convenience, RegexpSearch supports the following two modes:
 //  1. If re has no subgroups, return the position of the match for re itself.
 //  2. If re has one subgroup, return the position of the first subgroup.
 // It returns an error re is invalid, has more than one subgroup, or doesn't
 // match the buffer.
 func (e *Editor) RegexpSearch(bufName, re string) (Pos, error) {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 	buf, ok := e.buffers[bufName]
 	if !ok {
 		return Pos{}, ErrUnknownBuffer
 	}
 	start, _, err := regexpRange(buf.text(), re)
 	return start, err
 }

 // RegexpReplace edits the buffer corresponding to path by replacing the first
 // instance of re, or its first subgroup, with the replace text. See
 // RegexpSearch for more explanation of these two modes.
 // It returns an error if re is invalid, has more than one subgroup, or doesn't
 // match the buffer.
 func (e *Editor) RegexpReplace(ctx context.Context, path, re, replace string) error {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 	buf, ok := e.buffers[path]
 	if !ok {
 		return ErrUnknownBuffer
 	}
 	content := buf.text()
 	start, end, err := regexpRange(content, re)
 	if err != nil {
 		return err
 	}
 	return e.editBufferLocked(ctx, path, []Edit{{
 		Start: start,
 		End:   end,
 		Text:  replace,
 	}})
 }

 // EditBuffer applies the given test edits to the buffer identified by path.
 func (e *Editor) EditBuffer(ctx context.Context, path string, edits []Edit) error {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 	return e.editBufferLocked(ctx, path, edits)
 }

 // BufferText returns the content of the buffer with the given name.
 func (e *Editor) BufferText(name string) string {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 	return e.buffers[name].text()
 }

 // BufferVersion returns the current version of the buffer corresponding to
 // name (or 0 if it is not being edited).
 func (e *Editor) BufferVersion(name string) int {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 	return e.buffers[name].version
 }

 func (e *Editor) editBufferLocked(ctx context.Context, path string, edits []Edit) error {
 	buf, ok := e.buffers[path]
 	if !ok {
 		return fmt.Errorf("unknown buffer %q", path)
 	}
 	var (
 		content = make([]string, len(buf.content))
 		err     error
 		evts    []protocol.TextDocumentContentChangeEvent
 	)
 	copy(content, buf.content)
 	content, err = editContent(content, edits)
 	if err != nil {
 		return err
 	}

 	buf.content = content
 	buf.version++
 	e.buffers[path] = buf
 	// A simple heuristic: if there is only one edit, send it incrementally.
 	// Otherwise, send the entire content.
 	if len(edits) == 1 {
 		evts = append(evts, edits[0].toProtocolChangeEvent())
 	} else {
 		evts = append(evts, protocol.TextDocumentContentChangeEvent{
 			Text: buf.text(),
 		})
 	}
 	params := &protocol.DidChangeTextDocumentParams{
 		TextDocument: protocol.VersionedTextDocumentIdentifier{
 			Version:                float64(buf.version),
 			TextDocumentIdentifier: e.textDocumentIdentifier(buf.path),
 		},
 		ContentChanges: evts,
 	}
 	if e.server != nil {
 		if err := e.server.DidChange(ctx, params); err != nil {
 			return fmt.Errorf("DidChange: %w", err)
 		}
 	}
 	return nil
 }

 // GoToDefinition jumps to the definition of the symbol at the given position
 // in an open buffer.
 func (e *Editor) GoToDefinition(ctx context.Context, path string, pos Pos) (string, Pos, error) {
 	if err := e.checkBufferPosition(path, pos); err != nil {
 		return "", Pos{}, err
 	}
 	params := &protocol.DefinitionParams{}
 	params.TextDocument.URI = e.sandbox.Workdir.URI(path)
 	params.Position = pos.toProtocolPosition()

 	resp, err := e.server.Definition(ctx, params)
 	if err != nil {
 		return "", Pos{}, fmt.Errorf("definition: %w", err)
 	}
 	if len(resp) == 0 {
 		return "", Pos{}, nil
 	}
 	newPath := e.sandbox.Workdir.URIToPath(resp[0].URI)
 	newPos := fromProtocolPosition(resp[0].Range.Start)
 	if err := e.OpenFile(ctx, newPath); err != nil {
 		return "", Pos{}, fmt.Errorf("OpenFile: %w", err)
 	}
 	return newPath, newPos, nil
 }

 // OrganizeImports requests and performs the source.organizeImports codeAction.
 func (e *Editor) OrganizeImports(ctx context.Context, path string) error {
 	return e.codeAction(ctx, path, nil, protocol.SourceOrganizeImports)
 }

 // ApplyQuickFixes requests and performs the quickfix codeAction.
 func (e *Editor) ApplyQuickFixes(ctx context.Context, path string, diagnostics []protocol.Diagnostic) error {
 	return e.codeAction(ctx, path, diagnostics, protocol.QuickFix, protocol.SourceFixAll)
 }

 func (e *Editor) codeAction(ctx context.Context, path string, diagnostics []protocol.Diagnostic, only ...protocol.CodeActionKind) error {
 	if e.server == nil {
 		return nil
 	}
 	params := &protocol.CodeActionParams{}
 	params.TextDocument.URI = e.sandbox.Workdir.URI(path)
 	params.Context.Only = only
 	if diagnostics != nil {
 		params.Context.Diagnostics = diagnostics
 	}
 	actions, err := e.server.CodeAction(ctx, params)
 	if err != nil {
 		return fmt.Errorf("textDocument/codeAction: %w", err)
 	}
 	e.mu.Lock()
 	defer e.mu.Unlock()
 	for _, action := range actions {
 		var match bool
 		for _, o := range only {
 			if action.Kind == o {
 				match = true
 				break
 			}
 		}
 		if !match {
 			continue
 		}
 		for _, change := range action.Edit.DocumentChanges {
 			path := e.sandbox.Workdir.URIToPath(change.TextDocument.URI)
 			if float64(e.buffers[path].version) != change.TextDocument.Version {
 				// Skip edits for old versions.
 				continue
 			}
 			edits := convertEdits(change.Edits)
 			if err := e.editBufferLocked(ctx, path, edits); err != nil {
 				return fmt.Errorf("editing buffer %q: %w", path, err)
 			}
 		}
 	}
 	return nil
 }

 func convertEdits(protocolEdits []protocol.TextEdit) []Edit {
 	var edits []Edit
 	for _, lspEdit := range protocolEdits {
 		edits = append(edits, fromProtocolTextEdit(lspEdit))
 	}
 	return edits
 }

 // FormatBuffer gofmts a Go file.
 func (e *Editor) FormatBuffer(ctx context.Context, path string) error {
 	if e.server == nil {
 		return nil
 	}
 	e.mu.Lock()
 	version := e.buffers[path].version
 	e.mu.Unlock()
 	params := &protocol.DocumentFormattingParams{}
 	params.TextDocument.URI = e.sandbox.Workdir.URI(path)
 	resp, err := e.server.Formatting(ctx, params)
 	if err != nil {
 		return fmt.Errorf("textDocument/formatting: %w", err)
 	}
 	e.mu.Lock()
 	defer e.mu.Unlock()
 	if versionAfter := e.buffers[path].version; versionAfter != version {
 		return fmt.Errorf("before receipt of formatting edits, buffer version changed from %d to %d", version, versionAfter)
 	}
 	edits := convertEdits(resp)
 	return e.editBufferLocked(ctx, path, edits)
 }

 func (e *Editor) checkBufferPosition(path string, pos Pos) error {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 	buf, ok := e.buffers[path]
 	if !ok {
 		return fmt.Errorf("buffer %q is not open", path)
 	}
 	if !inText(pos, buf.content) {
 		return fmt.Errorf("position %v is invalid in buffer %q", pos, path)
 	}
 	return nil
 }

 // RunGenerate runs `go generate` non-recursively in the workdir-relative dir
 // path. It does not report any resulting file changes as a watched file
 // change, so must be followed by a call to Workdir.CheckForFileChanges once
 // the generate command has completed.
 func (e *Editor) RunGenerate(ctx context.Context, dir string) error {
 	if e.server == nil {
 		return nil
 	}
 	absDir := e.sandbox.Workdir.filePath(dir)
 	params := &protocol.ExecuteCommandParams{
 		Command:   "generate",
 		Arguments: []interface{}{absDir, false},
 	}
 	if _, err := e.server.ExecuteCommand(ctx, params); err != nil {
 		return fmt.Errorf("running generate: %v", err)
 	}
 	// Unfortunately we can't simply poll the workdir for file changes here,
 	// because server-side command may not have completed. In regtests, we can
 	// Await this state change, but here we must delegate that responsibility to
 	// the caller.
 	return nil
 }

 // CodeLens execute a codelens request on the server.
 func (e *Editor) CodeLens(ctx context.Context, path string) ([]protocol.CodeLens, error) {
 	if e.server == nil {
 		return nil, nil
 	}
 	e.mu.Lock()
 	_, ok := e.buffers[path]
 	e.mu.Unlock()
 	if !ok {
 		return nil, fmt.Errorf("buffer %q is not open", path)
 	}
 	params := &protocol.CodeLensParams{
 		TextDocument: e.textDocumentIdentifier(path),
 	}
 	lens, err := e.server.CodeLens(ctx, params)
 	if err != nil {
 		return nil, err
 	}
 	return lens, nil
 }
	// 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 fake

	import (
	"bufio"
	"context"
	"errors"
	"fmt"
	"regexp"
	"strings"
	"sync"

	"golang.org/x/tools/internal/jsonrpc2"
	"golang.org/x/tools/internal/lsp/protocol"
	)

	// Editor is a fake editor client. It keeps track of client state and can be
	// used for writing LSP tests.
	type Editor struct {
	Config EditorConfig

	// server, client, and sandbox are concurrency safe and written only
	// at construction time, so do not require synchronization.
	server protocol.Server
	client *Client
	sandbox *Sandbox

	// Since this editor is intended just for testing, we use very coarse
	// locking.
	mu sync.Mutex
	// Editor state.
	buffers map[string]buffer
	// Capabilities / Options
	serverCapabilities protocol.ServerCapabilities
	}

	type buffer struct {
	version int
	path string
	content []string
	}

	func (b buffer) text() string {
	return strings.Join(b.content, "\n")
	}

	// EditorConfig configures the editor's LSP session. This is similar to
	// source.UserOptions, but we use a separate type here so that we expose only
	// that configuration which we support.
	//
	// The zero value for EditorConfig should correspond to its defaults.
	type EditorConfig struct {
	Env []string

	// CodeLens is a map defining whether codelens are enabled, keyed by the
	// codeLens command. CodeLens which are not present in this map are left in
	// their default state.
	CodeLens map[string]bool

	// SymbolMatcher is the config associated with the "symbolMatcher" gopls
	// config option.
	SymbolMatcher *string
	}

	// NewEditor Creates a new Editor.
	func NewEditor(ws Sandbox, config EditorConfig) Editor {
	return &Editor{
	buffers: make(map[string]buffer),
	sandbox: ws,
	Config: config,
	}
	}

	// Connect configures the editor to communicate with an LSP server on conn. It
	// is not concurrency safe, and should be called at most once, before using the
	// editor.
	//
	// It returns the editor, so that it may be called as follows:
	// editor, err := NewEditor(s).Connect(ctx, conn)
	func (e Editor) Connect(ctx context.Context, conn jsonrpc2.Conn, hooks ClientHooks) (*Editor, error) {
	e.server = protocol.ServerDispatcher(conn)
	e.client = &Client{editor: e, hooks: hooks}
	go conn.Run(ctx,
	protocol.Handlers(
	protocol.ClientHandler(e.client,
	jsonrpc2.MethodNotFound)))
	if err := e.initialize(ctx); err != nil {
	return nil, err
	}
	e.sandbox.Workdir.AddWatcher(e.onFileChanges)
	return e, nil
	}

	// Shutdown issues the 'shutdown' LSP notification.
	func (e *Editor) Shutdown(ctx context.Context) error {
	if e.server != nil {
	if err := e.server.Shutdown(ctx); err != nil {
	return fmt.Errorf("Shutdown: %w", err)
	}
	}
	return nil
	}

	// Exit issues the 'exit' LSP notification.
	func (e *Editor) Exit(ctx context.Context) error {
	if e.server != nil {
	// Not all LSP clients issue the exit RPC, but we do so here to ensure that
	// we gracefully handle it on multi-session servers.
	if err := e.server.Exit(ctx); err != nil {
	return fmt.Errorf("Exit: %w", err)
	}
	}
	return nil
	}

	// Client returns the LSP client for this editor.
	func (e Editor) Client() Client {
	return e.client
	}

	func (e *Editor) configuration() map[string]interface{} {
	config := map[string]interface{}{
	"verboseWorkDoneProgress": true,
	}

	envvars := e.sandbox.GoEnv()
	envvars = append(envvars, e.Config.Env...)
	env := map[string]interface{}{}
	for _, value := range envvars {
	kv := strings.SplitN(value, "=", 2)
	env[kv[0]] = kv[1]
	}
	config["env"] = env

	if e.Config.CodeLens != nil {
	config["codelens"] = e.Config.CodeLens
	}

	if e.Config.SymbolMatcher != nil {
	config["symbolMatcher"] = *e.Config.SymbolMatcher
	}

	return config
	}

	func (e *Editor) initialize(ctx context.Context) error {
	params := &protocol.ParamInitialize{}
	params.ClientInfo.Name = "fakeclient"
	params.ClientInfo.Version = "v1.0.0"
	params.RootURI = e.sandbox.Workdir.RootURI()
	params.Capabilities.Workspace.Configuration = true
	params.Capabilities.Window.WorkDoneProgress = true
	// TODO: set client capabilities
	params.InitializationOptions = e.configuration()

	params.Trace = "messages"
	// TODO: support workspace folders.
	if e.server != nil {
	resp, err := e.server.Initialize(ctx, params)
	if err != nil {
	return fmt.Errorf("initialize: %w", err)
	}
	e.mu.Lock()
	e.serverCapabilities = resp.Capabilities
	e.mu.Unlock()

	if err := e.server.Initialized(ctx, &protocol.InitializedParams{}); err != nil {
	return fmt.Errorf("initialized: %w", err)
	}
	}
	// TODO: await initial configuration here, or expect gopls to manage that?
	return nil
	}

	func (e *Editor) onFileChanges(ctx context.Context, evts []FileEvent) {
	if e.server == nil {
	return
	}
	var lspevts []protocol.FileEvent
	for _, evt := range evts {
	lspevts = append(lspevts, evt.ProtocolEvent)
	}
	e.server.DidChangeWatchedFiles(ctx, &protocol.DidChangeWatchedFilesParams{
	Changes: lspevts,
	})
	}

	// OpenFile creates a buffer for the given workdir-relative file.
	func (e *Editor) OpenFile(ctx context.Context, path string) error {
	content, err := e.sandbox.Workdir.ReadFile(path)
	if err != nil {
	return err
	}
	buf := newBuffer(path, content)
	e.mu.Lock()
	e.buffers[path] = buf
	item := textDocumentItem(e.sandbox.Workdir, buf)
	e.mu.Unlock()

	if e.server != nil {
	if err := e.server.DidOpen(ctx, &protocol.DidOpenTextDocumentParams{
	TextDocument: item,
	}); err != nil {
	return fmt.Errorf("DidOpen: %w", err)
	}
	}
	return nil
	}

	func newBuffer(path, content string) buffer {
	return buffer{
	version: 1,
	path: path,
	content: strings.Split(content, "\n"),
	}
	}

	func textDocumentItem(wd *Workdir, buf buffer) protocol.TextDocumentItem {
	uri := wd.URI(buf.path)
	languageID := ""
	if strings.HasSuffix(buf.path, ".go") {
	// TODO: what about go.mod files? What is their language ID?
	languageID = "go"
	}
	return protocol.TextDocumentItem{
	URI: uri,
	LanguageID: languageID,
	Version: float64(buf.version),
	Text: buf.text(),
	}
	}

	// CreateBuffer creates a new unsaved buffer corresponding to the workdir path,
	// containing the given textual content.
	func (e *Editor) CreateBuffer(ctx context.Context, path, content string) error {
	buf := newBuffer(path, content)
	e.mu.Lock()
	e.buffers[path] = buf
	item := textDocumentItem(e.sandbox.Workdir, buf)
	e.mu.Unlock()

	if e.server != nil {
	if err := e.server.DidOpen(ctx, &protocol.DidOpenTextDocumentParams{
	TextDocument: item,
	}); err != nil {
	return fmt.Errorf("DidOpen: %w", err)
	}
	}
	return nil
	}

	// CloseBuffer removes the current buffer (regardless of whether it is saved).
	func (e *Editor) CloseBuffer(ctx context.Context, path string) error {
	e.mu.Lock()
	_, ok := e.buffers[path]
	if !ok {
	e.mu.Unlock()
	return ErrUnknownBuffer
	}
	delete(e.buffers, path)
	e.mu.Unlock()

	if e.server != nil {
	if err := e.server.DidClose(ctx, &protocol.DidCloseTextDocumentParams{
	TextDocument: e.textDocumentIdentifier(path),
	}); err != nil {
	return fmt.Errorf("DidClose: %w", err)
	}
	}
	return nil
	}

	func (e *Editor) textDocumentIdentifier(path string) protocol.TextDocumentIdentifier {
	return protocol.TextDocumentIdentifier{
	URI: e.sandbox.Workdir.URI(path),
	}
	}

	// SaveBuffer writes the content of the buffer specified by the given path to
	// the filesystem.
	func (e *Editor) SaveBuffer(ctx context.Context, path string) error {
	if err := e.OrganizeImports(ctx, path); err != nil {
	return fmt.Errorf("organizing imports before save: %w", err)
	}
	if err := e.FormatBuffer(ctx, path); err != nil {
	return fmt.Errorf("formatting before save: %w", err)
	}

	e.mu.Lock()
	buf, ok := e.buffers[path]
	if !ok {
	e.mu.Unlock()
	return fmt.Errorf(fmt.Sprintf("unknown buffer: %q", path))
	}
	content := buf.text()
	includeText := false
	syncOptions, ok := e.serverCapabilities.TextDocumentSync.(protocol.TextDocumentSyncOptions)
	if ok {
	includeText = syncOptions.Save.IncludeText
	}
	e.mu.Unlock()

	docID := e.textDocumentIdentifier(buf.path)
	if e.server != nil {
	if err := e.server.WillSave(ctx, &protocol.WillSaveTextDocumentParams{
	TextDocument: docID,
	Reason: protocol.Manual,
	}); err != nil {
	return fmt.Errorf("WillSave: %w", err)
	}
	}
	if err := e.sandbox.Workdir.WriteFile(ctx, path, content); err != nil {
	return fmt.Errorf("writing %q: %w", path, err)
	}
	if e.server != nil {
	params := &protocol.DidSaveTextDocumentParams{
	TextDocument: protocol.VersionedTextDocumentIdentifier{
	Version: float64(buf.version),
	TextDocumentIdentifier: docID,
	},
	}
	if includeText {
	params.Text = &content
	}
	if err := e.server.DidSave(ctx, params); err != nil {
	return fmt.Errorf("DidSave: %w", err)
	}
	}
	return nil
	}

	// contentPosition returns the (Line, Column) position corresponding to offset
	// in the buffer referenced by path.
	func contentPosition(content string, offset int) (Pos, error) {
	scanner := bufio.NewScanner(strings.NewReader(content))
	start := 0
	line := 0
	for scanner.Scan() {
	end := start + len([]rune(scanner.Text())) + 1
	if offset < end {
	return Pos{Line: line, Column: offset - start}, nil
	}
	start = end
	line++
	}
	if err := scanner.Err(); err != nil {
	return Pos{}, fmt.Errorf("scanning content: %w", err)
	}
	// Scan() will drop the last line if it is empty. Correct for this.
	if strings.HasSuffix(content, "\n") && offset == start {
	return Pos{Line: line, Column: 0}, nil
	}
	return Pos{}, fmt.Errorf("position %d out of bounds in %q (line = %d, start = %d)", offset, content, line, start)
	}

	// ErrNoMatch is returned if a regexp search fails.
	var (
	ErrNoMatch = errors.New("no match")
	ErrUnknownBuffer = errors.New("unknown buffer")
	)

	// regexpRange returns the start and end of the first occurrence of either re
	// or its singular subgroup. It returns ErrNoMatch if the regexp doesn't match.
	func regexpRange(content, re string) (Pos, Pos, error) {
	var start, end int
	rec, err := regexp.Compile(re)
	if err != nil {
	return Pos{}, Pos{}, err
	}
	indexes := rec.FindStringSubmatchIndex(content)
	if indexes == nil {
	return Pos{}, Pos{}, ErrNoMatch
	}
	switch len(indexes) {
	case 2:
	// no subgroups: return the range of the regexp expression
	start, end = indexes[0], indexes[1]
	case 4:
	// one subgroup: return its range
	start, end = indexes[2], indexes[3]
	default:
	return Pos{}, Pos{}, fmt.Errorf("invalid search regexp %q: expect either 0 or 1 subgroups, got %d", re, len(indexes)/2-1)
	}
	startPos, err := contentPosition(content, start)
	if err != nil {
	return Pos{}, Pos{}, err
	}
	endPos, err := contentPosition(content, end)
	if err != nil {
	return Pos{}, Pos{}, err
	}
	return startPos, endPos, nil
	}

	// RegexpSearch returns the position of the first match for re in the buffer
	// bufName. For convenience, RegexpSearch supports the following two modes:
	// 1. If re has no subgroups, return the position of the match for re itself.
	// 2. If re has one subgroup, return the position of the first subgroup.
	// It returns an error re is invalid, has more than one subgroup, or doesn't
	// match the buffer.
	func (e *Editor) RegexpSearch(bufName, re string) (Pos, error) {
	e.mu.Lock()
	defer e.mu.Unlock()
	buf, ok := e.buffers[bufName]
	if !ok {
	return Pos{}, ErrUnknownBuffer
	}
	start, _, err := regexpRange(buf.text(), re)
	return start, err
	}

	// RegexpReplace edits the buffer corresponding to path by replacing the first
	// instance of re, or its first subgroup, with the replace text. See
	// RegexpSearch for more explanation of these two modes.
	// It returns an error if re is invalid, has more than one subgroup, or doesn't
	// match the buffer.
	func (e *Editor) RegexpReplace(ctx context.Context, path, re, replace string) error {
	e.mu.Lock()
	defer e.mu.Unlock()
	buf, ok := e.buffers[path]
	if !ok {
	return ErrUnknownBuffer
	}
	content := buf.text()
	start, end, err := regexpRange(content, re)
	if err != nil {
	return err
	}
	return e.editBufferLocked(ctx, path, []Edit{{
	Start: start,
	End: end,
	Text: replace,
	}})
	}

	// EditBuffer applies the given test edits to the buffer identified by path.
	func (e *Editor) EditBuffer(ctx context.Context, path string, edits []Edit) error {
	e.mu.Lock()
	defer e.mu.Unlock()
	return e.editBufferLocked(ctx, path, edits)
	}

	// BufferText returns the content of the buffer with the given name.
	func (e *Editor) BufferText(name string) string {
	e.mu.Lock()
	defer e.mu.Unlock()
	return e.buffers[name].text()
	}

	// BufferVersion returns the current version of the buffer corresponding to
	// name (or 0 if it is not being edited).
	func (e *Editor) BufferVersion(name string) int {
	e.mu.Lock()
	defer e.mu.Unlock()
	return e.buffers[name].version
	}

	func (e *Editor) editBufferLocked(ctx context.Context, path string, edits []Edit) error {
	buf, ok := e.buffers[path]
	if !ok {
	return fmt.Errorf("unknown buffer %q", path)
	}
	var (
	content = make([]string, len(buf.content))
	err error
	evts []protocol.TextDocumentContentChangeEvent
	)
	copy(content, buf.content)
	content, err = editContent(content, edits)
	if err != nil {
	return err
	}

	buf.content = content
	buf.version++
	e.buffers[path] = buf
	// A simple heuristic: if there is only one edit, send it incrementally.
	// Otherwise, send the entire content.
	if len(edits) == 1 {
	evts = append(evts, edits[0].toProtocolChangeEvent())
	} else {
	evts = append(evts, protocol.TextDocumentContentChangeEvent{
	Text: buf.text(),
	})
	}
	params := &protocol.DidChangeTextDocumentParams{
	TextDocument: protocol.VersionedTextDocumentIdentifier{
	Version: float64(buf.version),
	TextDocumentIdentifier: e.textDocumentIdentifier(buf.path),
	},
	ContentChanges: evts,
	}
	if e.server != nil {
	if err := e.server.DidChange(ctx, params); err != nil {
	return fmt.Errorf("DidChange: %w", err)
	}
	}
	return nil
	}

	// GoToDefinition jumps to the definition of the symbol at the given position
	// in an open buffer.
	func (e *Editor) GoToDefinition(ctx context.Context, path string, pos Pos) (string, Pos, error) {
	if err := e.checkBufferPosition(path, pos); err != nil {
	return "", Pos{}, err
	}
	params := &protocol.DefinitionParams{}
	params.TextDocument.URI = e.sandbox.Workdir.URI(path)
	params.Position = pos.toProtocolPosition()

	resp, err := e.server.Definition(ctx, params)
	if err != nil {
	return "", Pos{}, fmt.Errorf("definition: %w", err)
	}
	if len(resp) == 0 {
	return "", Pos{}, nil
	}
	newPath := e.sandbox.Workdir.URIToPath(resp[0].URI)
	newPos := fromProtocolPosition(resp[0].Range.Start)
	if err := e.OpenFile(ctx, newPath); err != nil {
	return "", Pos{}, fmt.Errorf("OpenFile: %w", err)
	}
	return newPath, newPos, nil
	}

	// OrganizeImports requests and performs the source.organizeImports codeAction.
	func (e *Editor) OrganizeImports(ctx context.Context, path string) error {
	return e.codeAction(ctx, path, nil, protocol.SourceOrganizeImports)
	}

	// ApplyQuickFixes requests and performs the quickfix codeAction.
	func (e *Editor) ApplyQuickFixes(ctx context.Context, path string, diagnostics []protocol.Diagnostic) error {
	return e.codeAction(ctx, path, diagnostics, protocol.QuickFix, protocol.SourceFixAll)
	}

	func (e *Editor) codeAction(ctx context.Context, path string, diagnostics []protocol.Diagnostic, only ...protocol.CodeActionKind) error {
	if e.server == nil {
	return nil
	}
	params := &protocol.CodeActionParams{}
	params.TextDocument.URI = e.sandbox.Workdir.URI(path)
	params.Context.Only = only
	if diagnostics != nil {
	params.Context.Diagnostics = diagnostics
	}
	actions, err := e.server.CodeAction(ctx, params)
	if err != nil {
	return fmt.Errorf("textDocument/codeAction: %w", err)
	}
	e.mu.Lock()
	defer e.mu.Unlock()
	for _, action := range actions {
	var match bool
	for _, o := range only {
	if action.Kind == o {
	match = true
	break
	}
	}
	if !match {
	continue
	}
	for _, change := range action.Edit.DocumentChanges {
	path := e.sandbox.Workdir.URIToPath(change.TextDocument.URI)
	if float64(e.buffers[path].version) != change.TextDocument.Version {
	// Skip edits for old versions.
	continue
	}
	edits := convertEdits(change.Edits)
	if err := e.editBufferLocked(ctx, path, edits); err != nil {
	return fmt.Errorf("editing buffer %q: %w", path, err)
	}
	}
	}
	return nil
	}

	func convertEdits(protocolEdits []protocol.TextEdit) []Edit {
	var edits []Edit
	for _, lspEdit := range protocolEdits {
	edits = append(edits, fromProtocolTextEdit(lspEdit))
	}
	return edits
	}

	// FormatBuffer gofmts a Go file.
	func (e *Editor) FormatBuffer(ctx context.Context, path string) error {
	if e.server == nil {
	return nil
	}
	e.mu.Lock()
	version := e.buffers[path].version
	e.mu.Unlock()
	params := &protocol.DocumentFormattingParams{}
	params.TextDocument.URI = e.sandbox.Workdir.URI(path)
	resp, err := e.server.Formatting(ctx, params)
	if err != nil {
	return fmt.Errorf("textDocument/formatting: %w", err)
	}
	e.mu.Lock()
	defer e.mu.Unlock()
	if versionAfter := e.buffers[path].version; versionAfter != version {
	return fmt.Errorf("before receipt of formatting edits, buffer version changed from %d to %d", version, versionAfter)
	}
	edits := convertEdits(resp)
	return e.editBufferLocked(ctx, path, edits)
	}

	func (e *Editor) checkBufferPosition(path string, pos Pos) error {
	e.mu.Lock()
	defer e.mu.Unlock()
	buf, ok := e.buffers[path]
	if !ok {
	return fmt.Errorf("buffer %q is not open", path)
	}
	if !inText(pos, buf.content) {
	return fmt.Errorf("position %v is invalid in buffer %q", pos, path)
	}
	return nil
	}

	// RunGenerate runs `go generate` non-recursively in the workdir-relative dir
	// path. It does not report any resulting file changes as a watched file
	// change, so must be followed by a call to Workdir.CheckForFileChanges once
	// the generate command has completed.
	func (e *Editor) RunGenerate(ctx context.Context, dir string) error {
	if e.server == nil {
	return nil
	}
	absDir := e.sandbox.Workdir.filePath(dir)
	params := &protocol.ExecuteCommandParams{
	Command: "generate",
	Arguments: []interface{}{absDir, false},
	}
	if _, err := e.server.ExecuteCommand(ctx, params); err != nil {
	return fmt.Errorf("running generate: %v", err)
	}
	// Unfortunately we can't simply poll the workdir for file changes here,
	// because server-side command may not have completed. In regtests, we can
	// Await this state change, but here we must delegate that responsibility to
	// the caller.
	return nil
	}

	// CodeLens execute a codelens request on the server.
	func (e *Editor) CodeLens(ctx context.Context, path string) ([]protocol.CodeLens, error) {
	if e.server == nil {
	return nil, nil
	}
	e.mu.Lock()
	_, ok := e.buffers[path]
	e.mu.Unlock()
	if !ok {
	return nil, fmt.Errorf("buffer %q is not open", path)
	}
	params := &protocol.CodeLensParams{
	TextDocument: e.textDocumentIdentifier(path),
	}
	lens, err := e.server.CodeLens(ctx, params)
	if err != nil {
	return nil, err
	}
	return lens, nil
	}