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// 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 (
"bytes"
"context"
"crypto/sha256"
"fmt"
"io/fs"
"io/ioutil"
"os"
"path/filepath"
"runtime"
"sort"
"strings"
"sync"
"time"
"golang.org/x/tools/gopls/internal/lsp/protocol"
"golang.org/x/tools/gopls/internal/span"
"golang.org/x/tools/internal/robustio"
)
// RelativeTo is a helper for operations relative to a given directory.
type RelativeTo string
// AbsPath returns an absolute filesystem path for the workdir-relative path.
func (r RelativeTo) AbsPath(path string) string {
fp := filepath.FromSlash(path)
if filepath.IsAbs(fp) {
return fp
}
return filepath.Join(string(r), filepath.FromSlash(path))
}
// RelPath returns a '/'-encoded path relative to the working directory (or an
// absolute path if the file is outside of workdir)
func (r RelativeTo) RelPath(fp string) string {
root := string(r)
if rel, err := filepath.Rel(root, fp); err == nil && !strings.HasPrefix(rel, "..") {
return filepath.ToSlash(rel)
}
return filepath.ToSlash(fp)
}
// writeFileData writes content to the relative path, replacing the special
// token $SANDBOX_WORKDIR with the relative root given by rel. It does not
// trigger any file events.
func writeFileData(path string, content []byte, rel RelativeTo) error {
content = bytes.ReplaceAll(content, []byte("$SANDBOX_WORKDIR"), []byte(rel))
fp := rel.AbsPath(path)
if err := os.MkdirAll(filepath.Dir(fp), 0755); err != nil {
return fmt.Errorf("creating nested directory: %w", err)
}
backoff := 1 * time.Millisecond
for {
err := ioutil.WriteFile(fp, []byte(content), 0644)
if err != nil {
// This lock file violation is not handled by the robustio package, as it
// indicates a real race condition that could be avoided.
if isWindowsErrLockViolation(err) {
time.Sleep(backoff)
backoff *= 2
continue
}
return fmt.Errorf("writing %q: %w", path, err)
}
return nil
}
}
// isWindowsErrLockViolation reports whether err is ERROR_LOCK_VIOLATION
// on Windows.
var isWindowsErrLockViolation = func(err error) bool { return false }
// Workdir is a temporary working directory for tests. It exposes file
// operations in terms of relative paths, and fakes file watching by triggering
// events on file operations.
type Workdir struct {
RelativeTo
watcherMu sync.Mutex
watchers []func(context.Context, []protocol.FileEvent)
fileMu sync.Mutex
// File identities we know about, for the purpose of detecting changes.
//
// Since files is only used for detecting _changes_, we are tolerant of
// fileIDs that may have hash and mtime coming from different states of the
// file: if either are out of sync, then the next poll should detect a
// discrepancy. It is OK if we detect too many changes, but not OK if we miss
// changes.
//
// For that matter, this mechanism for detecting changes can still be flaky
// on platforms where mtime is very coarse (such as older versions of WSL).
// It would be much better to use a proper fs event library, but we can't
// currently import those into x/tools.
//
// TODO(golang/go#52284): replace this polling mechanism with a
// cross-platform library for filesystem notifications.
files map[string]fileID
}
// NewWorkdir writes the txtar-encoded file data in txt to dir, and returns a
// Workir for operating on these files using
func NewWorkdir(dir string, files map[string][]byte) (*Workdir, error) {
w := &Workdir{RelativeTo: RelativeTo(dir)}
for name, data := range files {
if err := writeFileData(name, data, w.RelativeTo); err != nil {
return nil, fmt.Errorf("writing to workdir: %w", err)
}
}
_, err := w.pollFiles() // poll files to populate the files map.
return w, err
}
// fileID identifies a file version on disk.
type fileID struct {
mtime time.Time
hash string // empty if mtime is old enough to be reliabe; otherwise a file digest
}
func hashFile(data []byte) string {
return fmt.Sprintf("%x", sha256.Sum256(data))
}
// RootURI returns the root URI for this working directory of this scratch
// environment.
func (w *Workdir) RootURI() protocol.DocumentURI {
return toURI(string(w.RelativeTo))
}
// AddWatcher registers the given func to be called on any file change.
func (w *Workdir) AddWatcher(watcher func(context.Context, []protocol.FileEvent)) {
w.watcherMu.Lock()
w.watchers = append(w.watchers, watcher)
w.watcherMu.Unlock()
}
// URI returns the URI to a the workdir-relative path.
func (w *Workdir) URI(path string) protocol.DocumentURI {
return toURI(w.AbsPath(path))
}
// URIToPath converts a uri to a workdir-relative path (or an absolute path,
// if the uri is outside of the workdir).
func (w *Workdir) URIToPath(uri protocol.DocumentURI) string {
fp := uri.SpanURI().Filename()
return w.RelPath(fp)
}
func toURI(fp string) protocol.DocumentURI {
return protocol.DocumentURI(span.URIFromPath(fp))
}
// ReadFile reads a text file specified by a workdir-relative path.
func (w *Workdir) ReadFile(path string) ([]byte, error) {
backoff := 1 * time.Millisecond
for {
b, err := ioutil.ReadFile(w.AbsPath(path))
if err != nil {
if runtime.GOOS == "plan9" && strings.HasSuffix(err.Error(), " exclusive use file already open") {
// Plan 9 enforces exclusive access to locked files.
// Give the owner time to unlock it and retry.
time.Sleep(backoff)
backoff *= 2
continue
}
return nil, err
}
return b, nil
}
}
// RegexpSearch searches the file corresponding to path for the first position
// matching re.
func (w *Workdir) RegexpSearch(path string, re string) (protocol.Location, error) {
content, err := w.ReadFile(path)
if err != nil {
return protocol.Location{}, err
}
mapper := protocol.NewMapper(w.URI(path).SpanURI(), content)
return regexpLocation(mapper, re)
}
// RemoveFile removes a workdir-relative file path and notifies watchers of the
// change.
func (w *Workdir) RemoveFile(ctx context.Context, path string) error {
fp := w.AbsPath(path)
if err := robustio.RemoveAll(fp); err != nil {
return fmt.Errorf("removing %q: %w", path, err)
}
return w.CheckForFileChanges(ctx)
}
// WriteFiles writes the text file content to workdir-relative paths and
// notifies watchers of the changes.
func (w *Workdir) WriteFiles(ctx context.Context, files map[string]string) error {
for path, content := range files {
fp := w.AbsPath(path)
_, err := os.Stat(fp)
if err != nil && !os.IsNotExist(err) {
return fmt.Errorf("checking if %q exists: %w", path, err)
}
if err := writeFileData(path, []byte(content), w.RelativeTo); err != nil {
return err
}
}
return w.CheckForFileChanges(ctx)
}
// WriteFile writes text file content to a workdir-relative path and notifies
// watchers of the change.
func (w *Workdir) WriteFile(ctx context.Context, path, content string) error {
return w.WriteFiles(ctx, map[string]string{path: content})
}
func (w *Workdir) fileEvent(path string, changeType protocol.FileChangeType) protocol.FileEvent {
return protocol.FileEvent{
URI: w.URI(path),
Type: changeType,
}
}
// RenameFile performs an on disk-renaming of the workdir-relative oldPath to
// workdir-relative newPath, and notifies watchers of the changes.
//
// oldPath must either be a regular file or in the same directory as newPath.
func (w *Workdir) RenameFile(ctx context.Context, oldPath, newPath string) error {
oldAbs := w.AbsPath(oldPath)
newAbs := w.AbsPath(newPath)
// For os.Rename, “OS-specific restrictions may apply when oldpath and newpath
// are in different directories.” If that applies here, we may fall back to
// ReadFile, WriteFile, and RemoveFile to perform the rename non-atomically.
//
// However, the fallback path only works for regular files: renaming a
// directory would be much more complex and isn't needed for our tests.
fallbackOk := false
if filepath.Dir(oldAbs) != filepath.Dir(newAbs) {
fi, err := os.Stat(oldAbs)
if err == nil && !fi.Mode().IsRegular() {
return &os.PathError{
Op: "RenameFile",
Path: oldPath,
Err: fmt.Errorf("%w: file is not regular and not in the same directory as %s", os.ErrInvalid, newPath),
}
}
fallbackOk = true
}
var renameErr error
const debugFallback = false
if fallbackOk && debugFallback {
renameErr = fmt.Errorf("%w: debugging fallback path", os.ErrInvalid)
} else {
renameErr = robustio.Rename(oldAbs, newAbs)
}
if renameErr != nil {
if !fallbackOk {
return renameErr // The OS-specific Rename restrictions do not apply.
}
content, err := w.ReadFile(oldPath)
if err != nil {
// If we can't even read the file, the error from Rename may be accurate.
return renameErr
}
fi, err := os.Stat(newAbs)
if err == nil {
if fi.IsDir() {
// “If newpath already exists and is not a directory, Rename replaces it.”
// But if it is a directory, maybe not?
return renameErr
}
// On most platforms, Rename replaces the named file with a new file,
// rather than overwriting the existing file it in place. Mimic that
// behavior here.
if err := robustio.RemoveAll(newAbs); err != nil {
// Maybe we don't have permission to replace newPath?
return renameErr
}
} else if !os.IsNotExist(err) {
// If the destination path already exists or there is some problem with it,
// the error from Rename may be accurate.
return renameErr
}
if writeErr := writeFileData(newPath, []byte(content), w.RelativeTo); writeErr != nil {
// At this point we have tried to actually write the file.
// If it still doesn't exist, assume that the error from Rename was accurate:
// for example, maybe we don't have permission to create the new path.
// Otherwise, return the error from the write, which may indicate some
// other problem (such as a full disk).
if _, statErr := os.Stat(newAbs); !os.IsNotExist(statErr) {
return writeErr
}
return renameErr
}
if err := robustio.RemoveAll(oldAbs); err != nil {
// If we failed to remove the old file, that may explain the Rename error too.
// Make a best effort to back out the write to the new path.
robustio.RemoveAll(newAbs)
return renameErr
}
}
return w.CheckForFileChanges(ctx)
}
// ListFiles returns a new sorted list of the relative paths of files in dir,
// recursively.
func (w *Workdir) ListFiles(dir string) ([]string, error) {
absDir := w.AbsPath(dir)
var paths []string
if err := filepath.Walk(absDir, func(fp string, info os.FileInfo, err error) error {
if err != nil {
return err
}
if info.Mode()&(fs.ModeDir|fs.ModeSymlink) == 0 {
paths = append(paths, w.RelPath(fp))
}
return nil
}); err != nil {
return nil, err
}
sort.Strings(paths)
return paths, nil
}
// CheckForFileChanges walks the working directory and checks for any files
// that have changed since the last poll.
func (w *Workdir) CheckForFileChanges(ctx context.Context) error {
evts, err := w.pollFiles()
if err != nil {
return err
}
if len(evts) == 0 {
return nil
}
w.watcherMu.Lock()
watchers := make([]func(context.Context, []protocol.FileEvent), len(w.watchers))
copy(watchers, w.watchers)
w.watcherMu.Unlock()
for _, w := range watchers {
w(ctx, evts)
}
return nil
}
// pollFiles updates w.files and calculates FileEvents corresponding to file
// state changes since the last poll. It does not call sendEvents.
func (w *Workdir) pollFiles() ([]protocol.FileEvent, error) {
w.fileMu.Lock()
defer w.fileMu.Unlock()
newFiles := make(map[string]fileID)
var evts []protocol.FileEvent
if err := filepath.Walk(string(w.RelativeTo), func(fp string, info os.FileInfo, err error) error {
if err != nil {
return err
}
// Skip directories and symbolic links (which may be links to directories).
//
// The latter matters for repos like Kubernetes, which use symlinks.
if info.Mode()&(fs.ModeDir|fs.ModeSymlink) != 0 {
return nil
}
// Opt: avoid reading the file if mtime is sufficently old to be reliable.
//
// If mtime is recent, it may not sufficiently identify the file contents:
// a subsequent write could result in the same mtime. For these cases, we
// must read the file contents.
id := fileID{mtime: info.ModTime()}
if time.Since(info.ModTime()) < 2*time.Second {
data, err := ioutil.ReadFile(fp)
if err != nil {
return err
}
id.hash = hashFile(data)
}
path := w.RelPath(fp)
newFiles[path] = id
if w.files != nil {
oldID, ok := w.files[path]
delete(w.files, path)
switch {
case !ok:
evts = append(evts, protocol.FileEvent{
URI: w.URI(path),
Type: protocol.Created,
})
case oldID != id:
changed := true
// Check whether oldID and id do not match because oldID was polled at
// a recent enough to time such as to require hashing.
//
// In this case, read the content to check whether the file actually
// changed.
if oldID.mtime.Equal(id.mtime) && oldID.hash != "" && id.hash == "" {
data, err := ioutil.ReadFile(fp)
if err != nil {
return err
}
if hashFile(data) == oldID.hash {
changed = false
}
}
if changed {
evts = append(evts, protocol.FileEvent{
URI: w.URI(path),
Type: protocol.Changed,
})
}
}
}
return nil
}); err != nil {
return nil, err
}
// Any remaining files must have been deleted.
for path := range w.files {
evts = append(evts, protocol.FileEvent{
URI: w.URI(path),
Type: protocol.Deleted,
})
}
w.files = newFiles
return evts, nil
}