io/fs, testing/testfs: disagreement about whether Open(".") must succeed

[josharian]

(Sorry for filing all these right around when 1.16 was released, not before. Just bad luck timing.)

I implemented what I thought was the simplest possible empty filesystem:

func (f *FS) Open(name string) (fs.File, error) {
	return nil, &fs.PathError{Op: "open", Path: name, Err: fs.ErrNotExist}
}

It seems to me that according to the io/fs docs, this is a valid empty filesystem.

testing/fstest.TestFS doesn't like it, though:

--- FAIL: TestEmptyFS (0.01s)
    fs_test.go:10: TestFS found errors:
        .: Open: open .: file does not exist

Is TestFS wrong? Or are there missing docs requiring the file "." to be openable?

cc @rsc

P.S. golang.org/s/owners doesn't list any owners for io/fs and testing/fstest.

[seankhliao]

I this it should be covered by:

the name "." may be used for the root directory.

As a directory, it must exist, and therefore be openable, even if it is empty.