Re: [PATCH] gitweb: Make git_get_refs_list do work of git_get_references

From: Junio C Hamano <junkio@cox.net>
Date: Sep 17, 2006, 02:12 UTC
Message-ID: <7vejub8cms.fsf@assigned-by-dhcp.cox.net>
In-Reply-To: <864pv7tgmx.fsf@blue.stonehenge.com>

merlyn@stonehenge.com (Randal L. Schwartz) writes:

Show 16 quoted lines

>>>>>> "Junio" == Junio C Hamano <junkio@cox.net> writes:
>
> Junio> Jakub Narebski <jnareb@gmail.com> writes:
>>> Make git_get_refs_list do also work of git_get_references, to avoid
>>> calling git-peek-remote twice. It now returns either list of refs as
>>> before in scalar context, or references hash and list of refs in list
>>> context.
>
> Junio> I do not think we want to have too many functions that return
> Junio> different things depending on contexts.  Forcing callers to
> Junio> remember what the function does in which context is bad.
>
> That's even an inaccurate description, so an expert in Perl (I've
> known a few) would just scratch his head.
>
> You cannot ever ever return a list in a scalar context.  Ever.  Never ever.

That much I think I know.

The code I was complaining about tries to do something like this:

	sub that_sub {
        	...
                return wantarray ? (\@bar, \%foo) : \@bar;
	}

and it is not done for optimization purposes (i.e. "if the caller only wants one and we are returning \@bar then we do not have to compute \%foo which is a big win" is not why it does this wantarray business).

So the callers when interested in the sequence of things in 'bar' typically say:

	my $the_list = that_sub(...);
        for (@$the_list) {
        	...
	}

while other callers say:

	my ($the_hash, $the_list) = that_sub(...);
	... use %$the_hash and @$the_list as see fit ...

And I was saying that getting rid of the "return wantwarray ? :" business and write the first class of callers like this

	my ($the_list) = that_sub(...);
        for (@$the_list) {
        	...
	}

would be much less confusing.