[asdf-devel] Feature-conditional components

[Faré]

1- ASDF has no such mechanism yet. Many people have asked for it (at
least nikodemus, manic12, and myself recently).
2- the feature feature was never working before I fixed and cerror'ed
it, and only does conditional *dependency* on another component, that
has to independently exist or conditionally exist, for which we have
no non-ugly mechanism.
3- the :if-component-dep-fails mechanism may or may not be working
well enough to do that right now, but man it's ugly, non-intuitive,
non-documented, and gross even if it were documented.
4- the very structure of ASDF objects doesn't allow a clean way of
expressing conditionally-included components, and this can't be added
as an extension (at least, not unless ASDF is extended to provide a
proper API, anyway). Doing anything more sophisticated than #+foo or
:if-component-dep-fails is going to be "interesting" and require major
work.
5- XCVB has such a mechanism, and I propose that if ASDF is to adopt
non-trivial conditionals, we should import XCVB's mini-language for
conditionals, if not the rest of it.
6- Hey - why not develop XCVB some more? Like, port it to your
favorite platform? I'd need a bit of help to make standalone backends
for Windows, including a committed hacker to port relevant parts of
IOLib to Windows.

[ François-René ÐVB Rideau | Reflection&Cybernethics | http://fare.tunes.org ]
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