lisp/loadhist.el

   1 ;;; loadhist.el --- lisp functions for working with feature groups
   2
   3 ;; Author: Eric S. Raymond <esr@snark.thyrsus.com>
   4 ;; Version: 1.0
   5 ;; Keywords: internal
   6
   7 ;;; Commentary:
   8
   9 ;; These functions exploit the load-history system variable.
  10 ;; Entry points include `unload-feature', `symbol-file', and `feature-file'.
  11
  12 ;;; Code:
  13
  14 (defun symbol-file (sym)
  15   "Return the input source from which SYM was loaded.
  16 This is a file name, or nil if the source was a buffer with no associated file."
  17   (catch 'foundit
  18     (mapcar
  19      (function (lambda (x) (if (memq sym (cdr x)) (throw 'foundit (car x)))))
  20      load-history)
  21     nil))
  22
  23 (defun feature-symbols (feature)
  24   "Return the file and list of symbols associated with a given FEATURE."
  25    (catch 'foundit
  26      (mapcar
  27       (function (lambda (x)
  28                   (if (member (cons 'provide feature) (cdr x))
  29                       (throw 'foundit x))))
  30       load-history)
  31      nil))
  32
  33 (defun feature-file (feature)
  34   "Return the file name from which a given FEATURE was loaded.
  35 Actually, return the load argument, if any; this is sometimes the name of a
  36 Lisp file without an extension.  If the feature came from an eval-buffer on
  37 a buffer with no associated file, or an eval-region, return nil."
  38   (if (not (featurep feature))
  39       (error "%s is not a currently loaded feature." (symbol-name feature))
  40     (car (feature-symbols feature))))
  41
  42 (defun file-provides (file)
  43   "Return the list of features provided by FILE."
  44   (let ((symbols (cdr (assoc file load-history))) (provides nil))
  45     (mapcar
  46      (function (lambda (x)
  47                  (if (and (consp x) (eq (car x) 'provide))
  48                      (setq provides (cons (cdr x) provides)))))
  49      symbols)
  50     provides
  51     ))
  52
  53 (defun file-requires (file)
  54   "Return the list of features required by FILE."
  55   (let ((symbols (cdr (assoc file load-history))) (requires nil))
  56     (mapcar
  57      (function (lambda (x)
  58                  (if (and (consp x) (eq (car x) 'require))
  59                      (setq requires (cons (cdr x) requires)))))
  60      symbols)
  61     requires
  62     ))
  63
  64 (defun set-intersect (p q)
  65   ;; Return the set intersection of two lists
  66   (let ((ret nil))
  67     (mapcar
  68      (function (lambda (x) (if (memq x q) (setq ret (cons x ret)))))
  69      p)
  70     ret
  71     ))
  72
  73 (defun file-dependents (file)
  74   ;; Return the list of loaded libraries that depend on FILE.
  75   (let ((provides (file-provides file)) (dependents nil))
  76     (mapcar
  77      (function (lambda (x)
  78                  (if (set-intersect provides (file-requires (car x)))
  79                      (setq dependents (cons (car x) dependents)))))
  80      load-history)
  81     dependents
  82     ))
  83
  84 ;;;###autoload
  85 (defun unload-feature (feature &optional force)
  86   "Unload the library that provided FEATURE, restoring all its autoloads.
  87 If the feature is required by any other loaded code, and optional FORCE
  88 is nil, raise an error."
  89   (interactive "SFeature: ")
  90   (if (not (featurep feature))
  91       (error "%s is not a currently loaded feature." (symbol-name feature)))
  92   (if (not force)
  93       (let* ((file (feature-file feature)) (dependents (file-dependents file)))
  94         (if dependents
  95             (error "Loaded libraries %s depend on %s."
  96                    (prin1-to-string dependents) file)
  97             )))
  98   (let* ((flist (feature-symbols feature)) (file (car flist)))
  99     (mapcar
 100      (function (lambda (x)
 101                  (cond ((stringp x) nil)
 102                        ((consp x) nil)
 103                        ((boundp x) (makunbound x))
 104                        ((fboundp x)
 105                         (fmakunbound x)
 106                         (let ((aload (get x 'autoload)))
 107                           (if aload (fset x aload))))))
 108                )
 109      (cdr flist))))
 110
 111 (provide 'loadhist)
 112
 113 ;;; loadhist.el ends here