os: RemoveAll no longer able to remove empty directory without read permission

[dmitshur]

There is a change in behavior of os.RemoveAll on tip compared to 1.11.2, on macOS (and Linux, BSDs), caused by CL 146020, in a specific scenario. I can't definitively say whether this change should considered a bug/regression, or if it's a normal intentional new behavior, so marking as NeedsDecision.

Prior to CL 146020, it was possible to use os.RemoveAll to remove an empty directory without read permissions, because its code had a "Simple case" as the first thing it tried:

func RemoveAll(path string) error {
	// Simple case: if Remove works, we're done.
	err := Remove(path)
	if err == nil || IsNotExist(err) {
		return nil
	}

	...

So the Go program https://play.golang.org/p/68OMhP1VS7G printed temp file was removed: true.

The new os.RemoveAll code after CL 146020 tries to read the directory before performing the "simple case", and returns a permission error instead:

$ go run .
temp file was removed: true
$ gotip run .
2018/12/11 16:14:39 os.RemoveAll: permission denied
exit status 1

/cc @ostenbom @ianlancetaylor

[bradfitz]

I think this is worth fixing for Go 1.12.

[gopherbot]

Change https://golang.org/cl/153720 mentions this issue: os: in RemoveAll, try Remove first