:FEATURE dependency-def

[Faré]

On Mon, May 16, 2016 at 3:35 PM, Robert Goldman <rpgoldman at sift.net> wrote:
> Is it just me, or is the :FEATURE dependency-def form undocumented in
> the manual?  It is *mentioned* in the grammar, but I don't see it
> documented -- except for the misleading mention that the :FEATURE
> *requirement* has been removed from ASDF.
>
There were two :FEATURE features. One was braindead and I removed it
in ASDF3, because it was badly breaking the object model.

> 1. if the FEATURE is present, include dependency-def and
> 2a. If the FEATURE is absent FAIL or
> 2b. If the FEATURE is absent, quietly succeed.
>
2b. Basically it's a (:when-feature :foocl "foocl-support")
Maybe it should have been named :when-feature,
but I believe the name was also from ASDF1, except that that feature
feature was badly broken and I had to fix it!

> If the semantics is intended to be the latter -- and that's how I read
> the relevant code in find-component.lisp -- how does a programmer say
> "if this feature is not present, my system should not compile"?
>
(:feature (:not :foocl) "something_that_fails")

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