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

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
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+15 −5
Original line number Diff line number Diff line
@@ -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*))