bug: sysopen() with O_NONBLOCK fatally croaks — flag missing from SUPPORTED_SYSOPEN_MODES

[toddr]

Summary

sysopen() on a mocked path dies with "Some of your permissions are not yet supported by Test::MockFile" whenever O_NONBLOCK (0x800) is part of the mode. O_NONBLOCK is not listed in SUPPORTED_SYSOPEN_MODES, and the mode-validation check confesses on any bit outside that whitelist.

Reproduction

use Fcntl;
use Test::MockFile qw< nostrict >;

my $dir = Test::MockFile->new_dir('/home/bob', { autovivify => 1 });

# Works (0xc1):
sysopen(my $ok, '/home/bob/a', O_WRONLY | O_CREAT | O_EXCL, 0600) or die "sysopen: $!";

# Dies (0x8c1):
#   Sorry, can't open /home/bob/b with 0x8c1 permissions.
#   Some of your permissions are not yet supported by Test::MockFile
sysopen(my $no, '/home/bob/b', O_WRONLY | O_CREAT | O_EXCL | O_NONBLOCK, 0600);

Cause

use constant SUPPORTED_SYSOPEN_MODES =>
    O_RDONLY | O_WRONLY | O_RDWR | O_APPEND | O_TRUNC | O_EXCL | O_CREAT | O_NOFOLLOW;
...
if ( ( $sysopen_mode & SUPPORTED_SYSOPEN_MODES ) != $sysopen_mode ) {
    confess( ... "Some of your permissions are not yet supported ..." );
}

O_NONBLOCK is absent from the whitelist, so any sysopen including it is fatal.

Impact

O_NONBLOCK is routinely OR'd into open flags for lock files and other guarded opens — it prevents blocking on FIFOs/devices and is harmless on regular files. For an in-memory mock it has no meaningful effect and can be safely accepted (and ignored). Today, any code under test that opens files with O_NONBLOCK cannot be exercised against mocked paths.

Suggested fix

Add O_NONBLOCK to SUPPORTED_SYSOPEN_MODES (accept-and-ignore). The same reasoning likely applies to O_CLOEXEC and O_NOCTTY, which are similarly benign for mocked files.

[toddr]

@toddr-bot fix