os: RemoveAll does not remove directories when ancestor directory lacks permissions

[neild]

This is a regression in Go 1.12 introduced by https://go-review.googlesource.com/c/137442 ("add support for long path names on unix RemoveAll").

mkdir -p a/1/x
mkdir -p a/2/x
chmod 0555 a

On Go 1.11, os.RemoveAll("a") removes a/1/x and a/2/x and returns "remove a/1: permission denied".
On Go 1.12, os.RemoveAll("a") returns "permission denied" and does not remove anything.

[bradfitz]

/cc @ianlancetaylor

[bradfitz]

This might be acceptable and just need docs. The current docs in the release notes only says:

RemoveAll now supports paths longer than 4096 characters on most Unix systems.

And, whoa, we no longer have docs on RemoveAll:

https://tip.golang.org/pkg/os/#RemoveAll

That needs to be fixed too.

[neild]

The docs for RemoveAll say:

// RemoveAll removes path and any children it contains.
// It removes everything it can but returns the first error
// it encounters. If the path does not exist, RemoveAll
// returns nil (no error).

So, not acceptable: RemoveAll no longer removes everything it can.

[neild]

The new RemoveAll is also skipping the call to testlog.Open.

[neild]

I'm also dubious about this distinction:

https://go.googlesource.com/go/+/master/src/os/removeall_at.go#132
https://go.googlesource.com/go/+/master/src/os/file_unix.go#207

The older RemoveAll uses os.Open to open directories, which includes a Darwin-specific retry loop around syscall.Open. The new RemoveAll uses unix.OpenAt with no retry loop. Perhaps that retry loop isn't necessary with OpenAt, but the lack of any commentary makes me wonder.

[gopherbot]

Change https://golang.org/cl/160180 mentions this issue: os: treat EACCES as a permission error in RemoveAll

[ianlancetaylor]

I believe that it's fine to skip the call to testlog.Open. It's only necessary to call testlog.Open if a change in the file contents affects whether a test should be cached. In this case it does not.

[gopherbot]

Change https://golang.org/cl/160181 mentions this issue: os: make openFdAt act like openFileNolog

[gopherbot]

Change https://golang.org/cl/160182 mentions this issue: os: add docs for _at version of RemoveAll