[asdf-devel] Re: Mistake (?) in grammar of defsystem

[Faré]

On Sat, Feb 22, 2014 at 5:53 PM, Robert P. Goldman <rpgoldman at sift.net> wrote:
> Thanks, Faré. Quick follow up: is there any construct that has semantics
> like "If this feature is not in features, fail"?
>
That's what the (feature <feature-expression>)
component-depends-on/in-order-to feature does.
Do you think it's useful?

On the other hand, I realize that, though it's never worked and is
probably never used,
the (:feature <feature-expression> <dependency-spec>) feature is
conceivably useful
for conditional dependencies of a system, as in this example from test-asdf.asd:

(defsystem :test-asdf/test-module-depend
  :depends-on
  ((:feature :sbcl (:require :sb-posix))
   (:feature :allegro (:require "osi")))
  ...)

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