Referencing subroutine in not-yet-loaded module

vsespb has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Referencing subroutine in not-yet-loaded module (ancient) by tye (Sage) on Nov 05, 2015 at 15:55 UTC
Being able to take a reference to a sub that has not yet been defined has been a feature in Perl "forever", and it seemed to me to not be an accidental result of some implementation detail. So I see no reason to go with a more complex approach. - tye	[reply]
Re: Referencing subroutine in not-yet-loaded module by GotToBTru (Prior) on Nov 05, 2015 at 13:42 UTC
The alternatives are .. is this good practice or is it a bug? That's confusing to me. You said it works .. but you are filing a bug report? That's even more confusing. Referencing a not yet loaded module in order to trigger loading on demand might be a great practice for saving on load time and memory requirements, but I would make sure this is well documented in your code. Dum Spiro Spero	[reply]
Re^2: Referencing subroutine in not-yet-loaded module by vsespb (Chaplain) on Nov 05, 2015 at 14:48 UTC
You said it works .. but you are filing a bug report? What works is references to subroutine in not-loaded packages. Bug report against Class::Load, which refuses to load packages after such referencing (thanks that I still have "require" working). is this good practice or is it a bug? Exactly. I think those are more probable alternatives. Referencing a not yet loaded module in order to trigger loading on demand might be a great practice for saving on load time and memory requirements I am not asking about such references in general, only about `\&NotYetLoadedModule::mysub();` vs `sub { &NotYetLoadedModule::mysub };`	[reply] [d/l] [select]
Re: Referencing subroutine in not-yet-loaded module by Anonymous Monk on Nov 05, 2015 at 10:32 UTC
Is this good practice to write or its a bug... Does it work? I am asking because after 1st example something is broken, and Class::Load::load_class refuses to load NotYetLoadedModule (this differs from require behaviour and thus I filed a bug report) Well, Class::Load isn't require The documentation is pretty clear, it uses "heuristics" to determine if a class is loaded, require doesn't do that, so not a bug in Class::Load behaviour ... its a documentation bug, it should document the actual heuristics, not make an allusion to the origin :) When I need to load I use the core Module::Load	[reply]
Re^2: Referencing subroutine in not-yet-loaded module by vsespb (Chaplain) on Nov 05, 2015 at 10:35 UTC
Does it work? yes. but that does not mean that it's a good practice.	[reply]
Re: Referencing subroutine in not-yet-loaded module by Anonymous Monk on Nov 06, 2015 at 21:36 UTC
The extra parentheses are not necessary (and indeed if you look at this expression in perl -MO=Deparse,-p you'll see they aren't being parsed at all how you expect): my $subref = \&NotYetLoadedModule::mysub; is fine. Class::Load looks in the symbol table in order to check if a module is "loaded" (this is to allow for inlined packages, that didn't come from a file). The issue was filed as https://rt.cpan.org/Ticket/Display.html?id=108388 and is not resolvable as this is simply how Class::Load works. Generally you're better off using Module::Runtime::require_module, which looks in %INC, a much more reliable mechanism to tell if a module has loaded. -ETHER (Karen Etheridge)	[reply]