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backend.go
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backend.go
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//go:build !darwin
// +build !darwin
package filewatcher
import (
"fmt"
"os"
"path/filepath"
"sync"
"github.com/fsnotify/fsnotify"
"github.com/hashicorp/go-hclog"
"github.com/karrick/godirwalk"
"github.com/pkg/errors"
"github.com/vercel/turbo/cli/internal/doublestar"
"github.com/vercel/turbo/cli/internal/fs"
"github.com/vercel/turbo/cli/internal/turbopath"
)
// watchAddMode is used to indicate whether watchRecursively should synthesize events
// for existing files.
type watchAddMode int
const (
dontSynthesizeEvents watchAddMode = iota
synthesizeEvents
)
type fsNotifyBackend struct {
watcher *fsnotify.Watcher
events chan Event
errors chan error
logger hclog.Logger
mu sync.Mutex
allExcludes []string
closed bool
}
func (f *fsNotifyBackend) Events() <-chan Event {
return f.events
}
func (f *fsNotifyBackend) Errors() <-chan error {
return f.errors
}
func (f *fsNotifyBackend) Close() error {
f.mu.Lock()
defer f.mu.Unlock()
if f.closed {
return ErrFilewatchingClosed
}
f.closed = true
close(f.events)
close(f.errors)
if err := f.watcher.Close(); err != nil {
return err
}
return nil
}
// onFileAdded helps up paper over cross-platform inconsistencies in fsnotify.
// Some fsnotify backends automatically add the contents of directories. Some do
// not. Adding a watch is idempotent, so anytime any file we care about gets added,
// watch it.
func (f *fsNotifyBackend) onFileAdded(name turbopath.AbsoluteSystemPath) error {
info, err := name.Lstat()
if err != nil {
if errors.Is(err, os.ErrNotExist) {
// We can race with a file being added and removed. Ignore it
return nil
}
return errors.Wrapf(err, "error checking lstat of new file %v", name)
}
if info.IsDir() {
// If a directory has been added, we need to synthesize events for everything it contains
if err := f.watchRecursively(name, []string{}, synthesizeEvents); err != nil {
return errors.Wrapf(err, "failed recursive watch of %v", name)
}
}
// Note that for symlinks and regular files, we don't add any watches, including traversing links
return nil
}
func (f *fsNotifyBackend) watchRecursively(root turbopath.AbsoluteSystemPath, excludePatterns []string, addMode watchAddMode) error {
f.mu.Lock()
defer f.mu.Unlock()
err := fs.WalkMode(root.ToString(), func(name string, isDir bool, info os.FileMode) error {
for _, excludePattern := range excludePatterns {
excluded, err := doublestar.Match(excludePattern, filepath.ToSlash(name))
if err != nil {
return err
}
if excluded {
return godirwalk.SkipThis
}
}
if info.IsDir() && (info&os.ModeSymlink == 0) {
if err := f.watcher.Add(name); err != nil {
return errors.Wrapf(err, "failed adding watch to %v", name)
}
f.logger.Debug(fmt.Sprintf("watching directory %v", name))
}
if addMode == synthesizeEvents {
f.events <- Event{
Path: fs.AbsoluteSystemPathFromUpstream(name),
EventType: FileAdded,
}
}
return nil
})
if err != nil {
return err
}
f.allExcludes = append(f.allExcludes, excludePatterns...)
return nil
}
func (f *fsNotifyBackend) watch() {
outer:
for {
select {
case ev, ok := <-f.watcher.Events:
if !ok {
break outer
}
eventType := toFileEvent(ev.Op)
path := fs.AbsoluteSystemPathFromUpstream(ev.Name)
if eventType == FileAdded {
if err := f.onFileAdded(path); err != nil {
f.errors <- err
}
}
if eventType == FileRenamed {
// synthesize a delete event for a rename
f.events <- Event{
Path: path,
EventType: FileDeleted,
}
}
f.events <- Event{
Path: path,
EventType: eventType,
}
case err, ok := <-f.watcher.Errors:
if !ok {
break outer
}
f.errors <- err
}
}
}
var _modifiedMask = fsnotify.Chmod | fsnotify.Write
func toFileEvent(op fsnotify.Op) FileEvent {
if op&fsnotify.Create != 0 {
return FileAdded
} else if op&fsnotify.Remove != 0 {
return FileDeleted
} else if op&_modifiedMask != 0 {
return FileModified
} else if op&fsnotify.Rename != 0 {
return FileRenamed
}
return FileOther
}
func (f *fsNotifyBackend) Start() error {
f.mu.Lock()
defer f.mu.Unlock()
if f.closed {
return ErrFilewatchingClosed
}
for _, dir := range f.watcher.WatchList() {
for _, excludePattern := range f.allExcludes {
excluded, err := doublestar.Match(excludePattern, filepath.ToSlash(dir))
if err != nil {
return err
}
if excluded {
if err := f.watcher.Remove(dir); err != nil {
return err
}
}
}
}
go f.watch()
return nil
}
func (f *fsNotifyBackend) AddRoot(root turbopath.AbsoluteSystemPath, excludePatterns ...string) error {
// We don't synthesize events for the initial watch
return f.watchRecursively(root, excludePatterns, dontSynthesizeEvents)
}
// GetPlatformSpecificBackend returns a filewatching backend appropriate for the OS we are
// running on.
func GetPlatformSpecificBackend(logger hclog.Logger) (Backend, error) {
watcher, err := fsnotify.NewWatcher()
if err != nil {
return nil, err
}
return &fsNotifyBackend{
watcher: watcher,
events: make(chan Event),
errors: make(chan error),
logger: logger.Named("fsnotify"),
}, nil
}