asdf::system-defsystem-depends-on sometimes slot-unbound

[Robert P. Goldman]

Fare writes:

[In order to identify] defsystem-depends-on dependencies,
there's asdf::system-defsystem-depends-on
aka asdf/system:system-defsystem-depends-on in ASDF3.
Unhappily, the slot is sometimes unbound (e.g. for preloaded systems),
which is probably a bug, and you need to
test for (slot-boundp system 'asdf::defsystem-depends-on)
(exported from asdf/component — why isn't it in asdf/system?
That's probably another bug. That said, it shouldn't be "just fixed"
without running the upgrade test —
I believe a :recycle asdf/component is then needed in asdf/system.
At the very least, it should be flagged for fixing
in case there's ever a backward-incompatible ASDF4).

[Faré (fahree)]

This is still unfixed. Robert: before release 3.1.1, maybe we should add an :initform nil to the defsystem-depends-on slot definition in asdf/system.lisp ?

[Robert P. Goldman (rpgoldman)]

Let me take a quick look at this before I say yea or nay -- I've been burned too many times by initforms. But I'm inclined to think this one is reasonable.

[Robert P. Goldman (rpgoldman)]

Does this only happen for preloaded systems? Do we have an example? I don't know how to replicate this bug.

[Faré (fahree)]

AFAICT, it's not a bug in the running code of ASDF, but a glitch in the exposed API: because the slot can be left unbound for regular systems as well as preloaded systems, users must check slot-boundp before they may use it.

Yes, it could be explicitly set for preloaded and regular systems alike, but it makes sense to have an :initform nil since that's a pretty good default indeed, and in practice also the default for regular systems.

(slot-boundp (asdf:find-system :alexandria) 'asdf::defsystem-depends-on)
;; => NIL

[Faré (fahree)]

NB: while you're at it, you might make Xach's life easier by separately and explicitly saving the :depends-on and :weakly-depends-on initialization arguments.

[Faré (fahree)]

It seems to me that rpgoldman fixed this bug in 3.1.0.68, with additional cleanup in 3.1.0.72. Marking as Fix Committed.