internal/lsp/fake: retry spurious file lock errors on windows

Cleaning the regtest sandbox sometimes fails on windows with errors that
may be spurious. Copy logic from the testing package to retry these
errors.

For golang/go#53819

Change-Id: I059fbb5e023af1cd52a5d231cd11a7c2ae72bc92
Reviewed-on: https://go-review.googlesource.com/c/tools/+/417117
Run-TryBot: Robert Findley <rfindley@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
gopls-CI: kokoro <noreply+kokoro@google.com>

internal/lsp/fake/sandbox.go

@@ -9,9 +9,11 @@ import (
 	"errors"
 	"fmt"
 	"io/ioutil"
+	"math/rand"
 	"os"
 	"path/filepath"
 	"strings"
+	"time"
 
 	"golang.org/x/tools/internal/gocommand"
 	"golang.org/x/tools/internal/testenv"
@@ -266,9 +268,36 @@ func (sb *Sandbox) Close() error {
 	if sb.gopath != "" {
 		goCleanErr = sb.RunGoCommand(context.Background(), "", "clean", []string{"-modcache"}, false)
 	}
-	err := os.RemoveAll(sb.rootdir)
+	err := removeAll(sb.rootdir)
 	if err != nil || goCleanErr != nil {
 		return fmt.Errorf("error(s) cleaning sandbox: cleaning modcache: %v; removing files: %v", goCleanErr, err)
 	}
 	return nil
 }
+
+// removeAll is copied from GOROOT/src/testing/testing.go
+//
+// removeAll is like os.RemoveAll, but retries Windows "Access is denied."
+// errors up to an arbitrary timeout.
+//
+// See https://go.dev/issue/50051 for additional context.
+func removeAll(path string) error {
+	const arbitraryTimeout = 2 * time.Second
+	var (
+		start     time.Time
+		nextSleep = 1 * time.Millisecond
+	)
+	for {
+		err := os.RemoveAll(path)
+		if !isWindowsRetryable(err) {
+			return err
+		}
+		if start.IsZero() {
+			start = time.Now()
+		} else if d := time.Since(start) + nextSleep; d >= arbitraryTimeout {
+			return err
+		}
+		time.Sleep(nextSleep)
+		nextSleep += time.Duration(rand.Int63n(int64(nextSleep)))
+	}
+}

internal/lsp/fake/workdir.go

@@ -77,6 +77,10 @@ func WriteFileData(path string, content []byte, rel RelativeTo) error {
 // on Windows.
 var isWindowsErrLockViolation = func(err error) bool { return false }
 
+// isWindowsRetryable reports whether err is a Windows error code
+// that may be fixed by retrying a failed filesystem operation.
+var isWindowsRetryable = 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.

internal/lsp/fake/workdir_windows.go

@@ -10,10 +10,31 @@ import (
 )
 
 func init() {
-	// from https://docs.microsoft.com/en-us/windows/win32/debug/system-error-codes--0-499-
-	const ERROR_LOCK_VIOLATION syscall.Errno = 33
+	// constants copied from GOROOT/src/internal/syscall/windows/syscall_windows.go
+	const (
+		ERROR_SHARING_VIOLATION syscall.Errno = 32
+		ERROR_LOCK_VIOLATION    syscall.Errno = 33
+	)
 
 	isWindowsErrLockViolation = func(err error) bool {
 		return errors.Is(err, ERROR_LOCK_VIOLATION)
 	}
+
+	// Copied from GOROOT/src/testing/testing_windows.go
+	isWindowsRetryable = func(err error) bool {
+		for {
+			unwrapped := errors.Unwrap(err)
+			if unwrapped == nil {
+				break
+			}
+			err = unwrapped
+		}
+		if err == syscall.ERROR_ACCESS_DENIED {
+			return true // Observed in https://go.dev/issue/50051.
+		}
+		if err == ERROR_SHARING_VIOLATION {
+			return true // Observed in https://go.dev/issue/51442.
+		}
+		return false
+	}
 }