[asdf-devel] Guard against (push "/foo/bar" asdf:*central-registry*)

[Gary King]

Hi Daniel,

I like your sketch but wonder about adding a second interface without  
removing the first. Since we shouldn't remove the first for both  
backwards compat and special variable goodness, I learn towards  
keeping things the same and running the checks late.

On Jul 10, 2009, at 11:37 PM, Daniel Herring wrote:

> 2009/7/10 Stelian Ionescu <sionescu at cddr.org>:
>> On Tue, 2009-07-07 at 12:31 +0200, Tobias C. Rittweiler wrote:
>>> I think it's bitten pretty much all of us that we at least once  
>>> tried to
>>> push a non-directory-designating filename to *CENTRAL-REGISTRY*.
>>>
>>> It's a common pitfalls for newcomers.
>>>
>>> Couldn't ASDF signal a warning when it encounters such a thing while
>>> grovelling through the registry?
>>
>> Why not simply deprecate(or unexport *CENTRAL-REGISTRY*) and add a
>> function REGISTER-ASDF-DIRECTORY that does all necessary checks ?
>
> I like the idea of adding a helper function.
>
> I don't like the idea of hiding *CENTRAL-REGISTRY*.  Given that asdf  
> needs
> a well-ordered list of directories to traverse (a la PATH on every  
> major
> OS), the current exported list provides a powerful API.
>
>
> Here's an actual case which greatly benefits from the registry being  
> an
> exported special variable.
>
> (let ((*central-registry* (list only-search-here)))
>  (if (asdf:operate 'asdf:load-op :test-package)
>      test-package-found-where-expected
>      error))
>
>
> Here's a quick sketch of two helpers that should handle most common  
> uses.
>
> (defun register-directory (path &optional (where :last) other)
>  (validate-or-die path)
>  (when other
>    (find-or-die other *central-registry*))
>  (when (find path *central-registry :test #'same-path)
>    (return))
>  (setf *central-registry*
>        (ccase where
>          (:first
>           (cons path *central-registry*))
>          (:last
>           (append *central-registry* (list path)))
>          (:before
>           (append paths-before-other
>                   (list path other)
>                   paths-after-other))
>          (:after
>           (append paths-before-other
>                   (list other path)
>                   paths-after-other)))))
> (defun deregister-directory (path)
>  (setf *central-registry*
>        (remove path *central-registry*)))
>
>
> Later,
> Daniel
>
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