Commit 0c95742b authored by Francois-Rene Rideau's avatar Francois-Rene Rideau

Commment on the bridges between systems and CL modules

The code was not clear enough why string-downcase is used at places,
and this notably confused Daniel Kochmański. See discussion at
asdf/asdf!13
parent 4e8b7ddc
......@@ -198,21 +198,31 @@ the implementation's REQUIRE rather than by internal ASDF mechanisms."))
(require module)))
(defmethod resolve-dependency-combination (component (combinator (eql :require)) arguments)
(unless (length=n-p arguments 1)
(error (compatfmt "~@<Bad dependency ~S for ~S. ~S takes only one argument~@:>")
(unless (and (length=n-p arguments 1)
(typep (car argument) '(or string (and symbol (not null)))))
(error (compatfmt "~@<Bad dependency ~S for ~S. ~S takes one argument, a string or non-null symbol~@:>")
(cons combinator arguments) component combinator))
;; :require must be prepared for some implementations providing modules using ASDF,
;; as SBCL used to do, and others may might do. Thus, the system provided in the end
;; would be a downcased name as per module-provide-asdf above. For the same reason,
;; we cannot assume that the system in the end will be of type require-system,
;; but must check whether we can use find-system and short-circuit cl:require.
;; Otherwise, calling cl:require could result in nasty reentrant calls between
;; cl:require and asdf:operate that could potentially blow up the stack.
(let* ((module (car arguments))
(name (string-downcase module))
(system (find-system name nil)))
(assert module)
;;(unless (typep system '(or null require-system))
;; (warn "~S depends on ~S but ~S is registered as a ~S"
;; component (cons combinator arguments) module (type-of system)))
(or system (let ((system (make-instance 'require-system :name name)))
(register-system system)
system))))
(defun module-provide-asdf (name)
;; We must use string-downcase, because modules are traditionally specified as symbols,
;; that implementations traditionally normalize as uppercase, for which we seek a system
;; with a name that is traditionally in lowercase. Case is lost along the way. That's fine.
;; We could make complex, non-portable rules to try to preserve case, and just documenting
;; them would be a hell that it would be a disservice to inflict on users.
(let ((module (string-downcase name)))
(unless (member module *modules-being-required* :test 'equal)
(let ((*modules-being-required* (cons module *modules-being-required*))
......
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