concurrent_dir_bug.p6

#!/usr/bin/env perl6

## Uncommenting the following line makes the bug disappear:
# my $*SCHEDULER = CurrentThreadScheduler;

## Set up a test folder with 26 empty files.
my $folder = "/tmp/concurrent_dir_bug".IO;
$folder.mkdir;
$folder.child("$_$_$_").spurt("") for "a".."z";

## Read the folder from multiple threads, and sanity-check each IO::Path.
## The sanity check should never fail, but at some point it does.
await do for ^20 {
    start {
        for $folder.dir -> $path {
            if $path.absolute ne $path.Str {
                die join "\n", <Str absolute gist perl>.map: {
                    "{.fmt: '%9s'}: {$path."$_"()}"
                }
            }
        }
    }
}

sample output

      Str: /tmp/concurrent_dir_bug/sss
 absolute: /tmp/concurrent_dir_bug/vvv
     gist: "/tmp/concurrent_dir_bug/vvv".IO
     perl: "/tmp/concurrent_dir_bug/vvv".IO(:SPEC(IO::Spec::Unix))
  in block <unit> at /home/sam/dev/concurrent_dir_bug.p6 line 13