listop operator causing infinite recursion, any way to fix? - raku

Question

I'm looking to possibly help update the File::HomeDir module which was never finished. While inspecting it, I noticed that stubbed out methods were causing infinite loops:
In the File::HomeDir role:
unit class File::HomeDir;
use File::HomeDir::Win32;
use File::HomeDir::MacOSX;
use File::HomeDir::Unix;
my File::HomeDir $singleton;
method new
{
return $singleton if $singleton.defined;
if $*DISTRO.is-win {
$singleton = self.bless does File::HomeDir::Win32;
} elsif $*DISTRO.name.starts-with('macos') {
$singleton = self.bless does File::HomeDir::MacOSX;
} else {
$singleton = self.bless does File::HomeDir::Unix;
}
return $singleton;
}
method my-home {
return File::HomeDir.new.my-home;
}
method my-desktop {
return File::HomeDir.new.my-desktop;
}
<snip>
In the File::HomeDir::MacOSX module:
use v6;
unit role File::HomeDir::MacOSX;
method my-home {
# Try HOME on every platform first, because even on Windows, some
# unix-style utilities rely on the ability to overload HOME.
return %*ENV<HOME> if %*ENV<HOME>.defined;
return;
}
method my-desktop {
!!!
}
<snip>
With this code, calling say File::HomeDir.my-desktop; results in an infinite loop.
This module was first written about 5 1/2 years ago. I'm assuming it worked at the time. But it appears now that if a role method has a listop operator, it causes the parent's class to be called which then called the role method which then calls the parent class, etc.

Answer 1

I'd do it like this, staying close to the original design:
role File::HomeDir::Win32 {
method my-home() { dd }
method my-desktop() { dd }
}
role File::HomeDir::MacOSX {
method my-home() { dd }
method my-desktop() { dd }
}
role File::HomeDir::Unix {
method my-home() { dd }
method my-desktop() { dd }
}
class File::HomeDir {
my $singleton;
# Return singleton, make one if there isn't one already
sub singleton() {
without $singleton {
$_ = File::HomeDir but $*DISTRO.is-win
?? File::HomeDir::Win32
!! $*DISTRO.name.starts-with('macos')
?? File::HomeDir::MacOSX
!! File::HomeDir::Unix;
}
$singleton
}
method my-home() { singleton.my-home }
method my-desktop() { singleton.my-desktop }
}
File::HomeDir.my-home;
File::HomeDir.my-desktop;