two greps on one supply

twogreps.p6

# When two greps are used on one supply, the one that matches is triggered twice.
# Run the following, then in the same directory `touch watchfile`
# Output:
#     got file change: "watchfile"
#     got file change: "watchfile"
# Expected output should only be a single line, not two.
# Each additional grep I add to the supply yields an additional output line.

my $paths = IO::Notification.watch_path('.')\
    .grep(*.event.isa(FileChangeEvent::FileChanged))\
    .unique(:as(*.path), :expires(5))\ 
    .map(*.path);

my $watch = $paths.grep(* ~~ /watchfile/)\
    .act(-> $x {             
        say "got file change: " ~ $x.perl;
    });                             
                                    
my $never = $paths.grep(* ~~ /shouldneverexecute/)\
    .act(-> $x {
        say "should never execute: " ~ $x.perl;
    });
   
sleep;    

I also tried testing this without using IO::Notification, and could not reproduce the bug.

my $s = Supply.new();

my $watch = $s.grep(* ~~ /1/)\
    .act(-> $x {    
        say "got one";
    });    

my $never = $s.grep(* ~~ /shouldneverexecute/)\
    .act(-> $x {
        say "should never execute";
    }); 

$s.emit(1);
$s.emit(2);

sleep;

# Output:
#   got one