find-system.lisp 26.8 KB
Newer Older
1 2 3
;;;; -------------------------------------------------------------------------
;;;; Finding systems

4
(uiop/package:define-package :asdf/find-system
5
  (:recycle :asdf/find-system :asdf)
6
  (:use :uiop/common-lisp :uiop :asdf/upgrade
7
    :asdf/cache :asdf/component :asdf/system)
8
  (:export
9
   #:remove-entry-from-registry #:coerce-entry-to-directory
10
   #:coerce-name #:primary-system-name #:coerce-filename
11
   #:find-system #:locate-system #:load-asd
12 13
   #:system-registered-p #:registered-system #:register-system
   #:registered-systems* #:registered-systems
14
   #:clear-system #:map-systems
15
   #:missing-component #:missing-requires #:missing-parent
16 17 18 19
   #: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
20
   #:find-system-if-being-defined
21
   #:contrib-sysdef-search #:sysdef-find-asdf ;; backward compatibility symbols, functions removed
22
   #:sysdef-preloaded-system-search #:register-preloaded-system #:*preloaded-systems*
23
   #:mark-component-preloaded ;; forward reference to asdf/operate
24 25
   #:sysdef-immutable-system-search #:register-immutable-system #:*immutable-systems*
   #:*defined-systems* #:clear-defined-systems
26
   ;; defined in source-registry, but specially mentioned here:
27
   #:initialize-source-registry #:sysdef-source-registry-search))
28 29
(in-package :asdf/find-system)

30
(with-upgradability ()
31
  (declaim (ftype (function (&optional t) t) initialize-source-registry)) ; forward reference
32 33 34 35 36 37 38 39 40

  (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)
41 42
               (apply 'format s (format-control c) (format-arguments c)))))

43 44 45 46 47 48 49
  (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)))))
50

51 52 53
  (defun sysdef-error (format &rest arguments)
    (error 'formatted-system-definition-error :format-control
           format :format-arguments arguments))
54

55 56 57

  ;;; Canonicalizing system names

58
  (defun coerce-name (name)
59 60 61
    "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)."
62 63
    (typecase name
      (component (component-name name))
64
      (symbol (string-downcase name))
65 66 67 68
      (string name)
      (t (sysdef-error (compatfmt "~@<Invalid component designator: ~3i~_~A~@:>") name))))

  (defun primary-system-name (name)
69 70 71
    "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."
72 73
    (first (split-string (coerce-name name) :separator "/")))

74
  (defun coerce-filename (name)
75 76 77 78
    "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."
79 80
    (frob-substrings (coerce-name name) '("/" ":" "\\") "--"))

81 82 83

  ;;; Registry of Defined Systems

84 85 86 87 88 89 90
  (defvar *defined-systems* (make-hash-table :test 'equal)
    "This is a hash table whose keys are strings, being the
names of the systems, and whose values are pairs, the first
element of which is a universal-time indicating when the
system definition was last updated, and the second element
of which is a system object.")

91
  (defun system-registered-p (name)
92 93 94
    "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."
95 96
    (gethash (coerce-name name) *defined-systems*))

97
  (defun registered-system (name)
Robert Goldman's avatar
Robert Goldman committed
98 99 100 101
    "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."
102 103
    (cdr (system-registered-p name)))

104
  (defun registered-systems* ()
105
    "Return a list containing every registered system (as a system object)."
106
    (loop :for registered :being :the :hash-values :of *defined-systems*
107 108 109
          :collect (cdr registered)))

  (defun registered-systems ()
110
    "Return a list of the names of every registered system."
111
    (mapcar 'coerce-name (registered-systems*)))
112 113

  (defun register-system (system)
114
    "Given a SYSTEM object, register it."
115 116 117 118
    (check-type system system)
    (let ((name (component-name system)))
      (check-type name string)
      (asdf-message (compatfmt "~&~@<; ~@;Registering ~3i~_~A~@:>~%") system)
119
      (unless (eq system (registered-system name))
120
        (setf (gethash name *defined-systems*)
121
              (cons (ignore-errors (get-file-stamp (system-source-file system)))
122 123
                    system)))))

124 125 126

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

127 128
  (defvar *preloaded-systems* (make-hash-table :test 'equal)
    "Registration table for preloaded systems.")
129

130
  (declaim (ftype (function (t) t) mark-component-preloaded)) ; defined in asdf/operate
131

132
  (defun make-preloaded-system (name keys)
133
    "Make a preloaded system of given NAME with build information from KEYS"
134 135 136 137 138
    (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))
139 140

  (defun sysdef-preloaded-system-search (requested)
141 142
    "If REQUESTED names a system registered as preloaded, return a new system
with its registration information."
143 144 145 146 147
    (let ((name (coerce-name requested)))
      (multiple-value-bind (keys foundp) (gethash name *preloaded-systems*)
        (when foundp
          (make-preloaded-system name keys)))))

148 149 150 151 152 153 154 155
  (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 ()
156 157
    "Make sure all registered preloaded systems are defined.
This function is run whenever ASDF is upgraded."
158 159 160 161
    (loop :for name :being :the :hash-keys :of *preloaded-systems*
          :do (ensure-preloaded-system-registered name)))
  (register-hook-function '*post-upgrade-restart-hook* 'ensure-all-preloaded-systems-registered)

162 163 164 165 166 167 168 169 170 171 172
  (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)))
173

174

175
  ;;; Immutable systems: in the image and can't be reloaded from source.
176 177

  (defvar *immutable-systems* nil
178
    "A hash-set (equal hash-table mapping keys to T) of systems that are immutable,
179 180 181
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.

182 183 184 185 186 187 188 189
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.")
190 191 192 193

  (defun sysdef-immutable-system-search (requested)
    (let ((name (coerce-name requested)))
      (when (and *immutable-systems* (gethash name *immutable-systems*))
194
        (or (registered-system requested)
195
            (error 'formatted-system-definition-error
196
                   :format-control "Requested system ~A registered as an immutable-system, ~
197
but not even registered as defined"
198 199
                   :format-arguments (list name))))))

200 201 202 203 204
(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)
205 206
      (unless *immutable-systems*
        (setf *immutable-systems* (list-to-hash-set nil)))
207 208 209 210
      (setf (gethash system-name *immutable-systems*) t)))


  ;;; Making systems undefined.
211 212

  (defun clear-system (system)
213 214 215
    "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
216
from which build details will have been cleared.
217
Note that this does NOT in any way cause any of the code of the system to be unloaded.
218
Returns T if system was or is now undefined, NIL if a new preloaded system was redefined."
219 220 221
    ;; 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.
222
    (let ((name (coerce-name system)))
223 224 225
      (remhash name *defined-systems*)
      (unset-asdf-cache-entry `(find-system ,name))
      (not (ensure-preloaded-system-registered name))))
226

227
  (defun clear-defined-systems ()
228
    (loop :for name :being :the :hash-keys :of *defined-systems*
229
          :unless (equal name "asdf") :do (clear-system name)))
230 231 232

  (register-hook-function '*post-upgrade-cleanup-hook* 'clear-defined-systems nil)

233 234
  (defun map-systems (fn)
    "Apply FN to each defined system.
235 236 237

FN should be a function of one argument. It will be
called with an object of type asdf:system."
238 239
    (loop :for registered :being :the :hash-values :of *defined-systems*
          :do (funcall fn (cdr registered)))))
240 241 242

;;; for the sake of keeping things reasonably neat, we adopt a
;;; convention that functions in this list are prefixed SYSDEF-
243 244 245 246 247 248 249
(with-upgradability ()
  (defvar *system-definition-search-functions* '())

  (defun cleanup-system-definition-search-functions ()
    (setf *system-definition-search-functions*
          (append
           ;; Remove known-incompatible sysdef functions from old versions of asdf.
250
           (remove-if #'(lambda (x) (member x '(contrib-sysdef-search sysdef-find-asdf sysdef-preloaded-system-search)))
251 252 253 254 255 256 257
                      *system-definition-search-functions*)
           ;; Tuck our defaults at the end of the list if they were absent.
           ;; This is imperfect, in case they were removed on purpose,
           ;; but then it will be the responsibility of whoever does that
           ;; 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
258
                        sysdef-source-registry-search)))))
259 260 261
  (cleanup-system-definition-search-functions)

  (defun search-for-system-definition (system)
262 263 264 265 266 267 268
    ;; 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*.
269 270 271
    (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)
272
        (try 'sysdef-immutable-system-search)
273
        (map () #'try *system-definition-search-functions*))))
274 275 276

  (defvar *central-registry* nil
    "A list of 'system directory designators' ASDF uses to find systems.
277 278 279 280 281 282 283 284 285

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/\"))

286
This is for backward compatibility.
287 288 289
Going forward, we recommend new users should be using the source-registry.
")

290
  (defun probe-asd (name defaults &key truename)
291
    (block nil
292 293 294 295 296 297 298 299 300
      (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(!)
301 302 303 304 305 306 307 308 309 310
        (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)))))))))
311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366

  (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))))))))))

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

  (defmethod find-system (name &optional (error-p t))
    (find-system (coerce-name name) error-p))

  (defun find-system-if-being-defined (name)
367 368 369 370 371 372 373
    ;; 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).
374
    (first (gethash `(find-system ,(coerce-name name)) *asdf-cache*)))
375

376 377 378
  (defun load-asd (pathname
                   &key name (external-format (encoding-external-format (detect-encoding pathname)))
                   &aux (readtable *readtable*) (print-pprint-dispatch *print-pprint-dispatch*))
379
    ;; Tries to load system definition with canonical NAME from PATHNAME.
380
    (with-asdf-cache ()
381 382
      (with-standard-io-syntax
        (let ((*package* (find-package :asdf-user))
383
              ;; Note that our backward-compatible *readtable* is
384
              ;; a global readtable that gets globally side-effected. Ouch.
385
              ;; Same for the *print-pprint-dispatch* table.
386 387
              ;; We should do something about that for ASDF3 if possible, or else ASDF4.
              (*readtable* readtable)
388
              (*print-pprint-dispatch* print-pprint-dispatch)
389 390 391
              (*print-readably* nil)
              (*default-pathname-defaults*
                ;; resolve logical-pathnames so they won't wreak havoc in parsing namestrings.
392
                (pathname-directory-pathname (physicalize-pathname pathname))))
393
          (handler-bind
394 395 396 397
              (((and error (not missing-component))
                 #'(lambda (condition)
                     (error 'load-system-definition-error
                            :name name :pathname pathname :condition condition))))
398 399
            (asdf-message (compatfmt "~&~@<; ~@;Loading system definition~@[ for ~A~] from ~A~@:>~%")
                          name pathname)
400
            (load* pathname :external-format external-format))))))
401

402 403 404 405 406 407 408 409 410
  (defvar *old-asdf-systems* (make-hash-table :test 'equal))

  (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)))
411 412 413 414 415 416 417 418 419 420 421
          (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 "~@<~
422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442
        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.~@:>~%"
443 444
                         old-version old-pathname version pathname))))
             nil))))) ;; only issue the warning the first time, but always return nil
445

446 447
  (defun locate-system (name)
    "Given a system NAME designator, try to locate where to load the system from.
448 449 450
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.
Robert P. Goldman's avatar
Robert P. Goldman committed
451 452
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,
453 454 455
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."
456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473
    (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)
474 475
          (check-type previous system) ;; asdf is preloaded, so there should be a previous one.
          (setf found-system nil pathname nil))
476
        (values foundp found-system pathname previous previous-time))))
477

478
  (defmethod find-system ((name string) &optional (error-p t))
479
    (with-asdf-cache (:key `(find-system ,name))
480 481 482
      (let ((primary-name (primary-system-name name)))
        (unless (equal name primary-name)
          (find-system primary-name nil)))
483
      (or (and *immutable-systems* (gethash name *immutable-systems*) (registered-system name))
484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502
          (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))))))
503
                ;; Only load when it's a pathname that is different or has newer content.
504
                (load-asd pathname :name name)))
505 506
            ;; Try again after having loaded from disk if needed
            (let ((in-memory (system-registered-p name)))
507 508 509 510 511 512 513
              (cond
                (in-memory
                 (when pathname
                   (setf (car in-memory) (get-file-stamp pathname)))
                 (cdr in-memory))
                (error-p
                 (error 'missing-component :requires name))
514
                (t
515
                 (return-from find-system nil)))))))))