find-system.lisp 29.3 KB
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;;;; -------------------------------------------------------------------------
;;;; Finding systems

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(uiop/package:define-package :asdf/find-system
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  (:recycle :asdf/find-system :asdf)
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  (:use :uiop/common-lisp :uiop :asdf/upgrade
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    :asdf/cache :asdf/component :asdf/system)
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  (:export
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   #:remove-entry-from-registry #:coerce-entry-to-directory
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   #:coerce-name #:primary-system-name #:coerce-filename
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   #:find-system #:locate-system #:load-asd
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   #:system-registered-p #:registered-system #:register-system
   #:registered-systems* #:registered-systems
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   #:clear-system #:map-systems
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   #:missing-component #:missing-requires #:missing-parent
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   #:formatted-system-definition-error #:format-control #:format-arguments #:sysdef-error
   #:load-system-definition-error #:error-name #:error-pathname #:error-condition
   #:*system-definition-search-functions* #:search-for-system-definition
   #:*central-registry* #:probe-asd #:sysdef-central-registry-search
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   #:find-system-if-being-defined
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   #:contrib-sysdef-search #:sysdef-find-asdf ;; backward compatibility symbols, functions removed
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   #:sysdef-preloaded-system-search #:register-preloaded-system #:*preloaded-systems*
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   #:mark-component-preloaded ;; forward reference to asdf/operate
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   #:sysdef-immutable-system-search #:register-immutable-system #:*immutable-systems*
   #:*defined-systems* #:clear-defined-systems
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   ;; defined in source-registry, but specially mentioned here:
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   #:initialize-source-registry #:sysdef-source-registry-search))
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(in-package :asdf/find-system)

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(with-upgradability ()
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  (declaim (ftype (function (&optional t) t) initialize-source-registry)) ; forward reference
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  (define-condition missing-component (system-definition-error)
    ((requires :initform "(unnamed)" :reader missing-requires :initarg :requires)
     (parent :initform nil :reader missing-parent :initarg :parent)))

  (define-condition formatted-system-definition-error (system-definition-error)
    ((format-control :initarg :format-control :reader format-control)
     (format-arguments :initarg :format-arguments :reader format-arguments))
    (:report (lambda (c s)
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               (apply 'format s (format-control c) (format-arguments c)))))

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  (define-condition load-system-definition-error (system-definition-error)
    ((name :initarg :name :reader error-name)
     (pathname :initarg :pathname :reader error-pathname)
     (condition :initarg :condition :reader error-condition))
    (:report (lambda (c s)
               (format s (compatfmt "~@<Error while trying to load definition for system ~A from pathname ~A: ~3i~_~A~@:>")
                       (error-name c) (error-pathname c) (error-condition c)))))
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  (defun sysdef-error (format &rest arguments)
    (error 'formatted-system-definition-error :format-control
           format :format-arguments arguments))
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  ;;; Canonicalizing system names

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  (defun coerce-name (name)
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    "Given a designator for a component NAME, return the name as a string.
The designator can be a COMPONENT (designing its name; note that a SYSTEM is a component),
a SYMBOL (designing its name, downcased), or a STRING (designing itself)."
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    (typecase name
      (component (component-name name))
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      (symbol (string-downcase name))
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      (string name)
      (t (sysdef-error (compatfmt "~@<Invalid component designator: ~3i~_~A~@:>") name))))

  (defun primary-system-name (name)
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    "Given a system designator NAME, return the name of the corresponding primary system,
after which the .asd file is named. That's the first component when dividing the name
as a string by / slashes."
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    (first (split-string (coerce-name name) :separator "/")))

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  (defun coerce-filename (name)
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    "Coerce a system designator NAME into a string suitable as a filename component.
The (current) transformation is to replace characters /:\\ each by --,
the former being forbidden in a filename component.
NB: The onus is unhappily on the user to avoid clashes."
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    (frob-substrings (coerce-name name) '("/" ":" "\\") "--"))

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  ;;; Registry of Defined Systems

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  (defvar *defined-systems* (make-hash-table :test 'equal)
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    "This is a hash table whose keys are strings -- the
names of systems -- and whose values are pairs, the first
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element of which is a universal-time indicating when the
system definition was last updated, and the second element
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of which is a system object.
  A system is referred to as \"registered\" if it is present
in this table.")
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  (defun system-registered-p (name)
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    "Return a generalized boolean that is true if a system of given NAME was registered already.
NAME is a system designator, to be normalized by COERCE-NAME.
The value returned if true is a pair of a timestamp and a system object."
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    (gethash (coerce-name name) *defined-systems*))

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  (defun registered-system (name)
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    "Return a system of given NAME that was registered already,
if such a system exists.  NAME is a system designator, to be
normalized by COERCE-NAME. The value returned is a system object,
or NIL if not found."
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    (cdr (system-registered-p name)))

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  (defun registered-systems* ()
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    "Return a list containing every registered system (as a system object)."
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    (loop :for registered :being :the :hash-values :of *defined-systems*
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          :collect (cdr registered)))

  (defun registered-systems ()
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    "Return a list of the names of every registered system."
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    (mapcar 'coerce-name (registered-systems*)))
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  (defun register-system (system)
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    "Given a SYSTEM object, register it."
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    (check-type system system)
    (let ((name (component-name system)))
      (check-type name string)
      (asdf-message (compatfmt "~&~@<; ~@;Registering ~3i~_~A~@:>~%") system)
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      (unless (eq system (registered-system name))
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        (setf (gethash name *defined-systems*)
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              (cons (ignore-errors (get-file-stamp (system-source-file system)))
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                    system)))))

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  ;;; Preloaded systems: in the image even if you can't find source files backing them.

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  (defvar *preloaded-systems* (make-hash-table :test 'equal)
    "Registration table for preloaded systems.")
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  (declaim (ftype (function (t) t) mark-component-preloaded)) ; defined in asdf/operate
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  (defun make-preloaded-system (name keys)
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    "Make a preloaded system of given NAME with build information from KEYS"
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    (let ((system (apply 'make-instance (getf keys :class 'system)
                         :name name :source-file (getf keys :source-file)
                         (remove-plist-keys '(:class :name :source-file) keys))))
      (mark-component-preloaded system)
      system))
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  (defun sysdef-preloaded-system-search (requested)
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    "If REQUESTED names a system registered as preloaded, return a new system
with its registration information."
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    (let ((name (coerce-name requested)))
      (multiple-value-bind (keys foundp) (gethash name *preloaded-systems*)
        (when foundp
          (make-preloaded-system name keys)))))

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  (defun ensure-preloaded-system-registered (name)
    "If there isn't a registered _defined_ system of given NAME,
and a there is a registered _preloaded_ system of given NAME,
then define and register said preloaded system."
    (if-let (system (and (not (registered-system name)) (sysdef-preloaded-system-search name)))
      (register-system system)))

  (defun ensure-all-preloaded-systems-registered ()
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    "Make sure all registered preloaded systems are defined.
This function is run whenever ASDF is upgraded."
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    (loop :for name :being :the :hash-keys :of *preloaded-systems*
          :do (ensure-preloaded-system-registered name)))
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  (register-hook-function '*post-upgrade-cleanup-hook* 'ensure-all-preloaded-systems-registered)
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  (defun register-preloaded-system (system-name &rest keys &key (version t) &allow-other-keys)
    "Register a system as being preloaded. If the system has not been loaded from the filesystem
yet, or if its build information is later cleared with CLEAR-SYSTEM, a dummy system will be
registered without backing filesystem information, based on KEYS (e.g. to provide a VERSION).
If VERSION is the default T, and a system was already loaded, then its version will be preserved."
    (let ((name (coerce-name system-name)))
      (when (eql version t)
        (if-let (system (registered-system name))
          (setf (getf keys :version) (component-version system))))
      (setf (gethash name *preloaded-systems*) keys)
      (ensure-preloaded-system-registered system-name)))
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  ;;; Immutable systems: in the image and can't be reloaded from source.
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  (defvar *immutable-systems* nil
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    "A hash-set (equal hash-table mapping keys to T) of systems that are immutable,
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i.e. already loaded in memory and not to be refreshed from the filesystem.
They will be treated specially by find-system, and passed as :force-not argument to make-plan.

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For instance, to can deliver an image with many systems precompiled, that *will not* check the
filesystem for them every time a user loads an extension, what more risk a problematic upgrade
 or catastrophic downgrade, before you dump an image, you may use:
   (map () 'asdf:register-immutable-system (asdf:already-loaded-systems))

Note that direct access to this variable from outside ASDF is not supported.
Please call REGISTER-IMMUTABLE-SYSTEM to add new immutable systems, and
contact maintainers if you need a stable API to do more than that.")
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  (defun sysdef-immutable-system-search (requested)
    (let ((name (coerce-name requested)))
      (when (and *immutable-systems* (gethash name *immutable-systems*))
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        (or (registered-system requested)
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            (error 'formatted-system-definition-error
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                   :format-control "Requested system ~A registered as an immutable-system, ~
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but not even registered as defined"
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                   :format-arguments (list name))))))

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(defun register-immutable-system (system-name &rest keys)
  "Register SYSTEM-NAME as preloaded and immutable.
It will automatically be considered as passed to FORCE-NOT in a plan."
    (let ((system-name (coerce-name system-name)))
      (apply 'register-preloaded-system system-name keys)
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      (unless *immutable-systems*
        (setf *immutable-systems* (list-to-hash-set nil)))
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      (setf (gethash system-name *immutable-systems*) t)))


  ;;; Making systems undefined.
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  (defun clear-system (system)
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    "Clear the entry for a SYSTEM in the database of systems previously defined.
However if the system was registered as PRELOADED (which it is if it is IMMUTABLE),
then a new system with the same name will be defined and registered in its place
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from which build details will have been cleared.
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Note that this does NOT in any way cause any of the code of the system to be unloaded.
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Returns T if system was or is now undefined, NIL if a new preloaded system was redefined."
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    ;; There is no "unload" operation in Common Lisp, and
    ;; a general such operation cannot be portably written,
    ;; considering how much CL relies on side-effects to global data structures.
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    (let ((name (coerce-name system)))
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      (remhash name *defined-systems*)
      (unset-asdf-cache-entry `(find-system ,name))
      (not (ensure-preloaded-system-registered name))))
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  (defun clear-defined-systems ()
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    "Clear all currently registered defined systems.
Preloaded systems (including immutable ones) will be reset, other systems will be de-registered."
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    (loop :for name :being :the :hash-keys :of *defined-systems*
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          :unless (equal name "asdf") :do (clear-system name)))
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  (register-hook-function '*post-upgrade-cleanup-hook* 'clear-defined-systems nil)

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  (defun map-systems (fn)
    "Apply FN to each defined system.
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FN should be a function of one argument. It will be
called with an object of type asdf:system."
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    (loop :for registered :being :the :hash-values :of *defined-systems*
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          :do (funcall fn (cdr registered))))
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  ;;; Searching for system definitions

  ;; For the sake of keeping things reasonably neat, we adopt a convention that
  ;; only symbols are to be pushed to this list (rather than e.g. function objects),
  ;; which makes upgrade easier. Also, the name of these symbols shall start with SYSDEF-
  (defvar *system-definition-search-functions* '()
    "A list that controls the ways that ASDF looks for system definitions.
It contains symbols to be funcalled in order, with a requested system name as argument,
until one returns a non-NIL result (if any), which must then be a fully initialized system object
with that name.")

  ;; Initialize and/or upgrade the *system-definition-search-functions*
  ;; so it doesn't contain obsolete symbols, and does contain the current ones.
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  (defun cleanup-system-definition-search-functions ()
    (setf *system-definition-search-functions*
          (append
           ;; Remove known-incompatible sysdef functions from old versions of asdf.
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           ;; Order matters, so we can't just use set-difference.
           (let ((obsolete
                  '(contrib-sysdef-search sysdef-find-asdf sysdef-preloaded-system-search)))
             (remove-if #'(lambda (x) (member x obsolete)) *system-definition-search-functions*))
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           ;; Tuck our defaults at the end of the list if they were absent.
           ;; This is imperfect, in case they were removed on purpose,
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           ;; but then it will be the responsibility of whoever removes these symmbols
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           ;; to upgrade asdf before he does such a thing rather than after.
           (remove-if #'(lambda (x) (member x *system-definition-search-functions*))
                      '(sysdef-central-registry-search
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                        sysdef-source-registry-search)))))
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  (cleanup-system-definition-search-functions)

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  ;; This (private) function does the search for a system definition using *s-d-s-f*;
  ;; it is to be called by locate-system.
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  (defun search-for-system-definition (system)
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    ;; Search for valid definitions of the system available in the current session.
    ;; Previous definitions as registered in *defined-systems* MUST NOT be considered;
    ;; they will be reconciled by locate-system then find-system.
    ;; There are two special treatments: first, specially search for objects being defined
    ;; in the current session, to avoid definition races between several files;
    ;; second, specially search for immutable systems, so they cannot be redefined.
    ;; Finally, use the search functions specified in *system-definition-search-functions*.
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    (let ((name (coerce-name system)))
      (flet ((try (f) (if-let ((x (funcall f name))) (return-from search-for-system-definition x))))
        (try 'find-system-if-being-defined)
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        (try 'sysdef-immutable-system-search)
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        (map () #'try *system-definition-search-functions*))))
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  ;;; The legacy way of finding a system: the *central-registry*

  ;; This variable contains a list of directories to be lazily searched for the requested asd
  ;; by sysdef-central-registry-search.
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  (defvar *central-registry* nil
    "A list of 'system directory designators' ASDF uses to find systems.
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A 'system directory designator' is a pathname or an expression
which evaluates to a pathname. For example:

    (setf asdf:*central-registry*
          (list '*default-pathname-defaults*
                #p\"/home/me/cl/systems/\"
                #p\"/usr/share/common-lisp/systems/\"))

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This variable is for backward compatibility.
Going forward, we recommend new users should be using the source-registry.")
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  ;; Function to look for an asd file of given NAME under a directory provided by DEFAULTS.
  ;; Return the truename of that file if it is found and TRUENAME is true.
  ;; Return NIL if the file is not found.
  ;; On Windows, follow shortcuts to .asd files.
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  (defun probe-asd (name defaults &key truename)
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    (block nil
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      (when (directory-pathname-p defaults)
        (if-let (file (probe-file*
                       (ensure-absolute-pathname
                        (parse-unix-namestring name :type "asd")
                        #'(lambda () (ensure-absolute-pathname defaults 'get-pathname-defaults nil))
                        nil)
                       :truename truename))
          (return file))
        #-(or clisp genera) ; clisp doesn't need it, plain genera doesn't have read-sequence(!)
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        (os-cond
         ((os-windows-p)
          (when (physical-pathname-p defaults)
            (let ((shortcut
                    (make-pathname
                     :defaults defaults :case :local
                     :name (strcat name ".asd")
                     :type "lnk")))
              (when (probe-file* shortcut)
                (ensure-pathname (parse-windows-shortcut shortcut) :namestring :native)))))))))
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  ;; Function to push onto *s-d-s-f* to use the *central-registry*
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  (defun sysdef-central-registry-search (system)
    (let ((name (primary-system-name system))
          (to-remove nil)
          (to-replace nil))
      (block nil
        (unwind-protect
             (dolist (dir *central-registry*)
               (let ((defaults (eval dir))
                     directorized)
                 (when defaults
                   (cond ((directory-pathname-p defaults)
                          (let* ((file (probe-asd name defaults :truename *resolve-symlinks*)))
                            (when file
                              (return file))))
                         (t
                          (restart-case
                              (let* ((*print-circle* nil)
                                     (message
                                       (format nil
                                               (compatfmt "~@<While searching for system ~S: ~3i~_~S evaluated to ~S which is not an absolute directory.~@:>")
                                               system dir defaults)))
                                (error message))
                            (remove-entry-from-registry ()
                              :report "Remove entry from *central-registry* and continue"
                              (push dir to-remove))
                            (coerce-entry-to-directory ()
                              :test (lambda (c) (declare (ignore c))
                                      (and (not (directory-pathname-p defaults))
                                           (directory-pathname-p
                                            (setf directorized
                                                  (ensure-directory-pathname defaults)))))
                              :report (lambda (s)
                                        (format s (compatfmt "~@<Coerce entry to ~a, replace ~a and continue.~@:>")
                                                directorized dir))
                              (push (cons dir directorized) to-replace))))))))
          ;; cleanup
          (dolist (dir to-remove)
            (setf *central-registry* (remove dir *central-registry*)))
          (dolist (pair to-replace)
            (let* ((current (car pair))
                   (new (cdr pair))
                   (position (position current *central-registry*)))
              (setf *central-registry*
                    (append (subseq *central-registry* 0 position)
                            (list new)
                            (subseq *central-registry* (1+ position))))))))))

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  ;;; Methods for find-system

  ;; Reject NIL as a system designator.
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  (defmethod find-system ((name null) &optional (error-p t))
    (when error-p
      (sysdef-error (compatfmt "~@<NIL is not a valid system name~@:>"))))

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  ;; Default method for find-system: resolve the argument using COERCE-NAME.
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  (defmethod find-system (name &optional (error-p t))
    (find-system (coerce-name name) error-p))

  (defun find-system-if-being-defined (name)
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    ;; This function finds systems being defined *in the current ASDF session*, as embodied by
    ;; its session cache, even before they are fully defined and registered in *defined-systems*.
    ;; The purpose of this function is to prevent races between two files that might otherwise
    ;; try overwrite each other's system objects, resulting in infinite loops and stack overflow.
    ;; This function explicitly MUST NOT find definitions merely registered in previous sessions.
    ;; NB: this function depends on a corresponding side-effect in parse-defsystem;
    ;; the precise protocol between the two functions may change in the future (or not).
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    (first (gethash `(find-system ,(coerce-name name)) *asdf-cache*)))
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  (defun load-asd (pathname
                   &key name (external-format (encoding-external-format (detect-encoding pathname)))
                   &aux (readtable *readtable*) (print-pprint-dispatch *print-pprint-dispatch*))
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    "Load system definitions from PATHNAME.
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NAME if supplied is the name of a system expected to be defined in that file.

Do NOT try to load a .asd file directly with CL:LOAD. Always use ASDF:LOAD-ASD."
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    (with-asdf-cache ()
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      (with-standard-io-syntax
        (let ((*package* (find-package :asdf-user))
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              ;; Note that our backward-compatible *readtable* is
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              ;; a global readtable that gets globally side-effected. Ouch.
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              ;; Same for the *print-pprint-dispatch* table.
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              ;; We should do something about that for ASDF3 if possible, or else ASDF4.
              (*readtable* readtable)
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              (*print-pprint-dispatch* print-pprint-dispatch)
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              (*print-readably* nil)
              (*default-pathname-defaults*
                ;; resolve logical-pathnames so they won't wreak havoc in parsing namestrings.
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                (pathname-directory-pathname (physicalize-pathname pathname))))
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          (handler-bind
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              (((and error (not missing-component))
                 #'(lambda (condition)
                     (error 'load-system-definition-error
                            :name name :pathname pathname :condition condition))))
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            (asdf-message (compatfmt "~&~@<; ~@;Loading system definition~@[ for ~A~] from ~A~@:>~%")
                          name pathname)
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            (load* pathname :external-format external-format))))))
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  (defvar *old-asdf-systems* (make-hash-table :test 'equal))

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  ;; (Private) function to check that a system that was found isn't an asdf downgrade.
  ;; Returns T if everything went right, NIL if the system was an ASDF of the same or older version,
  ;; that shall not be loaded. Also issue a warning if it was a strictly older version of ASDF.
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  (defun check-not-old-asdf-system (name pathname)
    (or (not (equal name "asdf"))
        (null pathname)
        (let* ((version-pathname (subpathname pathname "version.lisp-expr"))
               (version (and (probe-file* version-pathname :truename nil)
                             (read-file-form version-pathname)))
               (old-version (asdf-version)))
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          (cond
            ((version< old-version version) t) ;; newer version: good!
            ((equal old-version version) nil) ;; same version: don't load, but don't warn
            (t ;; old version: bad
             (ensure-gethash
              (list (namestring pathname) version) *old-asdf-systems*
              #'(lambda ()
                 (let ((old-pathname
                         (if-let (pair (system-registered-p "asdf"))
                           (system-source-file (cdr pair)))))
                   (warn "~@<~
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        You are using ASDF version ~A ~:[(probably from (require \"asdf\") ~
        or loaded by quicklisp)~;from ~:*~S~] and have an older version of ASDF ~
        ~:[(and older than 2.27 at that)~;~:*~A~] registered at ~S. ~
        Having an ASDF installed and registered is the normal way of configuring ASDF to upgrade itself, ~
        and having an old version registered is a configuration error. ~
        ASDF will ignore this configured system rather than downgrade itself. ~
        In the future, you may want to either: ~
        (a) upgrade this configured ASDF to a newer version, ~
        (b) install a newer ASDF and register it in front of the former in your configuration, or ~
        (c) uninstall or unregister this and any other old version of ASDF from your configuration. ~
        Note that the older ASDF might be registered implicitly through configuration inherited ~
        from your system installation, in which case you might have to specify ~
        :ignore-inherited-configuration in your in your ~~/.config/common-lisp/source-registry.conf ~
        or other source-registry configuration file, environment variable or lisp parameter. ~
        Indeed, a likely offender is an obsolete version of the cl-asdf debian or ubuntu package, ~
        that you might want to upgrade (if a recent enough version is available) ~
        or else remove altogether (since most implementations ship with a recent asdf); ~
        if you lack the system administration rights to upgrade or remove this package, ~
        then you might indeed want to either install and register a more recent version, ~
        or use :ignore-inherited-configuration to avoid registering the old one. ~
        Please consult ASDF documentation and/or experts.~@:>~%"
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                         old-version old-pathname version pathname))))
             nil))))) ;; only issue the warning the first time, but always return nil
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  (defun locate-system (name)
    "Given a system NAME designator, try to locate where to load the system from.
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Returns five values: FOUNDP FOUND-SYSTEM PATHNAME PREVIOUS PREVIOUS-TIME
FOUNDP is true when a system was found,
either a new unregistered one or a previously registered one.
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FOUND-SYSTEM when not null is a SYSTEM object that may be REGISTER-SYSTEM'ed.
PATHNAME when not null is a path from which to load the system,
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either associated with FOUND-SYSTEM, or with the PREVIOUS system.
PREVIOUS when not null is a previously loaded SYSTEM object of same name.
PREVIOUS-TIME when not null is the time at which the PREVIOUS system was loaded."
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    (with-asdf-cache () ;; NB: We don't cache the results. We once used to, but it wasn't useful,
      ;; and keeping a negative cache was a bug (see lp#1335323), which required
      ;; explicit invalidation in clear-system and find-system (when unsucccessful).
      (let* ((name (coerce-name name))
             (in-memory (system-registered-p name)) ; load from disk if absent or newer on disk
             (previous (cdr in-memory))
             (previous (and (typep previous 'system) previous))
             (previous-time (car in-memory))
             (found (search-for-system-definition name))
             (found-system (and (typep found 'system) found))
             (pathname (ensure-pathname
                        (or (and (typep found '(or pathname string)) (pathname found))
                            (and found-system (system-source-file found-system))
                            (and previous (system-source-file previous)))
                        :want-absolute t :resolve-symlinks *resolve-symlinks*))
             (foundp (and (or found-system pathname previous) t)))
        (check-type found (or null pathname system))
        (unless (check-not-old-asdf-system name pathname)
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          (check-type previous system) ;; asdf is preloaded, so there should be a previous one.
          (setf found-system nil pathname nil))
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        (values foundp found-system pathname previous previous-time))))
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  ;; Main method for find-system: first, make sure the computation is memoized in a session cache.
  ;; unless the system is immutable, use locate-system to find the primary system;
  ;; reconcile the finding (if any) with any previous definition (in a previous session,
  ;; preloaded, with a previous configuration, or before filesystem changes), and
  ;; load a found .asd if appropriate. Finally, update registration table and return results.
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  (defmethod find-system ((name string) &optional (error-p t))
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    (with-asdf-cache (:key `(find-system ,name))
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      (let ((primary-name (primary-system-name name)))
        (unless (equal name primary-name)
          (find-system primary-name nil)))
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      (or (and *immutable-systems* (gethash name *immutable-systems*) (registered-system name))
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          (multiple-value-bind (foundp found-system pathname previous previous-time)
              (locate-system name)
            (assert (eq foundp (and (or found-system pathname previous) t)))
            (let ((previous-pathname (and previous (system-source-file previous)))
                  (system (or previous found-system)))
              (when (and found-system (not previous))
                (register-system found-system))
              (when (and system pathname)
                (setf (system-source-file system) pathname))
              (when (and pathname
                         (let ((stamp (get-file-stamp pathname)))
                           (and stamp
                                (not (and previous
                                          (or (pathname-equal pathname previous-pathname)
                                              (and pathname previous-pathname
                                                   (pathname-equal
                                                    (physicalize-pathname pathname)
                                                    (physicalize-pathname previous-pathname))))
                                          (stamp<= stamp previous-time))))))
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                ;; Only load when it's a pathname that is different or has newer content.
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                (load-asd pathname :name name)))
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            ;; Try again after having loaded from disk if needed
            (let ((in-memory (system-registered-p name)))
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              (cond
                (in-memory
                 (when pathname
                   (setf (car in-memory) (get-file-stamp pathname)))
                 (cdr in-memory))
                (error-p
                 (error 'missing-component :requires name))
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                (t
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                 (return-from find-system nil)))))))))