Implement ishidden on ZFS for BSD

[jakewilliami]

See also: #3, #13.

[jakewilliami]

I should consider implementing on OpenBSD and NetBSD, not just FreeBSD. However, Julia itself only officially supports FreeBSD, so we will see.

[jakewilliami]

Interestingly, using the _st_flags check, running _isinvisible on FreeBSD on /mnt/Media/.zfs/ returns false, but mounting it onto my macOS, calling _isinvisible on /Volumes/Media/.zfs/ returns true. Perhaps it's my construction of the stat struct. Will investigate.

[jakewilliami]

Some more testing: we run the following on FreeBSD:

#include  <stdio.h>
#include <sys/stat.h>

int main() {
    char *fd = "/mnt/.zfs";
    struct stat statbuf;
    stat(fd, &statbuf);
    unsigned int isinvisible = statbuf.st_flags & ((unsigned int) 32768);  /* 0x00008000 */
    printf("%u\n", isinvisible);
    return 0;
}

And this returns:

$ cc test.c && ./a.out
0

So perhaps the uv stat struct is fine, but the behaviour itself on FreeBSD is different to when it's on macOS. That would make sense.

[jakewilliami]

After some further testing, I believe the jl_lstat call is working as expected:

Path	st_flags (C)	st_flags (Julia)
/mnt/.zfs	0x000	0x000
/mnt	0x800	0x800
/root/projects	0x800	0x800
/root/.bashrc	0x800	0x800
/usr/lib	0x800	0x800
/usr/local/bin/bash	0x800	0x800
/dev	0x000	0x000

Hence, it does seem that out uv stat call is working well. However, this does expose a greater question: is does st_flags ever actually expose hidden files on FreeBSD? The answer appears to be no: I ran the following script and had nothing print:

using HiddenFiles

function HiddenFiles._isinvisible(fs::Vector{String}; show_true::Bool = true)
    for f in fs
        i = HiddenFiles._isinvisible(f)
        show_true && i && println(f)
    end
end

function main(root_path::AbstractString)
    for (root, dirs, files) in walkdir(root_path, follow_symlinks=true, onerror=println)
        try
            _isinvisible(joinpath.(root, files))
        catch
            continue
        end
    end
end

main("/")

However, the st_flags attribute does appear to be set, at least, so that must imply that it's possible that we can derive an answer from st_flags on FreeBSD.

Further testing should check if this flag is being set on Linux. Perhaps this check should be a global UNIX thing?

This comment pertains to #3.

[jakewilliami]

Considering how long it has taken me to get literally nowhere regarding this implementation, I think I would like to save this feature for a different version, in the interest of getting a useable package registered.