[asdf-devel] :ASDF-DEPENDENCIES implemented

[Juan Jose Garcia-Ripoll]

On Sun, Apr 18, 2010 at 4:56 PM, Robert Goldman <rpgoldman at sift.info> wrote:

> So:  what is the intended effect of :ASDF-DEPENDENCIES and
> :ASDF-OPTIONAL-DEPENDENCIES?  At what point in the processing of the
> DEFSYSTEM are they processed?  How do they interact with the processing
> of other DEFSYSTEM initargs?  The answers to these questions should not
> be left to reading the code.
>

This depends on the level of implementation we achieve.

Ideally the situation could be such that the loading of dependencies could
be delayed until the system is actually used. In other words, load the
system definition using the base class, record components, dependencies,
etc, Only when the system is actually loaded, compute the dependencies which
are present and can be used and change the class using the extensions which
are really available.

In practice it might not be that simple. There are situations right now in
which it might have been useful to load the dependency _before_ even reading
the system definition. These situations require further fixes:

- Right now people are using symbols in other packages.
  Solution: prevent this by specification; prefixed symbols should be
strings and apply the previous rule

- Some systems use conditional reading #+/#-
  Solution: fix the use of :FEATURE in the DEFSYSTEM specification

- Some systems use #. plus functions they define
  Solution: use another readtable.

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