[asdf-devel] patch system-source-file

[Greg Pfeil]

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On 9 Jul 2009, at 13:08, Robert Goldman wrote:

> Greg Pfeil wrote:
>> Here are a couple changes to ASDF that I made in the process of  
>> creating
>> an ASDF browser for CCL's IDE:
>>
>> ∙ system-source-file now works for systems without their own .asd
>> ∙ optional parts of systems (version, maintainer, etc.) don't leave
>> their slots unbound
>
> The first of these looks good, but I'm less fond of the second change.
> I've been bitten repeatedly by bugs caused by initforms that caused
> slots not explicitly set to have some value that hides a mistaken
> failure to fill the slot.

Yeah, I should have sent these as separate patches. The first one is  
more important, IMO, and the second is definitely debatable.

> I'd rather have us handle slot-unbound on those optional parts of the
> system instead of stuffing a bunch of NILs in there.

When you say "us", do you mean implementing the accessors explicitly  
in ASDF to handle the condition, or having the caller handle/avoid the  
condition?

> If one is expecting strings here one must still handle checking for  
> NIL,
> so having to check for slot-boundp doesn't seem that much more  
> onerous.

Checking slot-boundp has a number of problems:

∙ you have to export the slot names
∙ it breaks the accessor abstraction because the slot names don't  
match the accessor names
	(when (slot-boundp foo 'asdf::description) (system-description foo))
∙ it breaks the accessor abstraction again because not everything that  
follows the accessor pattern has a slot
	(when (slot-boundp foo 'asdf::pathname) (component-pathname foo))

The default value could just as well be "" as NIL. I chose NIL because  
you can kind of distinguish a system explicitly having "" as the value  
versus the case where the slot isn't set. If the distinction isn't  
worthwhile (which it probably isn't in this case, "" may be just as  
good.

> On a related topic, I'd be inclined, more for documentation than
> efficiency, to stick :type string on a bunch of these.  Of course, if
> I'm wrong about the above, this would have to be (or null string)....


Or use "" as the default.

Again, this is much less important to me than the system-source-file  
change (well, other than the fact that I'm loath to use non-exported  
symbols in CCL), so if that could be committed separately, I'd  
appreciate it. I'm happy to send a new diff with only those changes if  
that would help.
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