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[bpt/emacs.git] / lisp / loadhist.el

diff --git a/lisp/loadhist.el b/lisp/loadhist.el
index e609596..8cbe1d8 100644 (file)
--- a/lisp/loadhist.el
+++ b/lisp/loadhist.el
@@ -98,7 +98,8 @@ return the feature \(symbol\)."
                                   features)
                           nil t)))
 
-(defvar loadhist-hook-functions
+(defvaralias 'loadhist-hook-functions 'unload-feature-special-hooks)
+(defvar unload-feature-special-hooks
   '(after-change-functions
     after-insert-file-functions auto-fill-function
     before-change-functions blink-paren-function
@@ -115,11 +116,27 @@ These are symbols with hook-type values whose names don't end in
 `-hook' or `-hooks', from which `unload-feature' tries to remove
 pertinent symbols.")
 
+(defvar unload-hook-features-list nil
+  "List of features of the package being unloaded.
+
+This is meant to be used by FEATURE-unload-hook hooks, see the
+documentation of `unload-feature' for details.")
+
 ;;;###autoload
 (defun unload-feature (feature &optional force)
   "Unload the library that provided FEATURE, restoring all its autoloads.
 If the feature is required by any other loaded code, and prefix arg FORCE
-is nil, raise an error."
+is nil, raise an error.
+
+This function tries to undo modifications made by the package to
+hooks.  Packages may define a hook FEATURE-unload-hook that is called
+instead of the normal heuristics for doing this.  Such a hook should
+undo all the relevant global state changes that may have been made by
+loading the package or executing functions in it.  It has access to
+the package's feature list (before anything is unbound) in the
+variable `unload-hook-features-list' and could remove features from it
+in the event that the package has done something normally-ill-advised,
+such as redefining an Emacs function."
   (interactive (list (read-feature "Feature: ") current-prefix-arg))
   (if (not (featurep feature))
       (error "%s is not a currently loaded feature" (symbol-name feature)))
@@ -129,15 +146,15 @@ is nil, raise an error."
        (if dependents
            (error "Loaded libraries %s depend on %s"
                   (prin1-to-string dependents) file))))
-  (let* ((flist (feature-symbols feature))
-         (file (car flist))
+  (let* ((unload-hook-features-list (feature-symbols feature))
+         (file (car unload-hook-features-list))
          (unload-hook (intern-soft (concat (symbol-name feature)
                                            "-unload-hook"))))
     ;; Try to avoid losing badly when hooks installed in critical
     ;; places go away.  (Some packages install things on
     ;; `kill-buffer-hook', `activate-menubar-hook' and the like.)
-    ;; First off, provide a clean way for package `foo' to arrange
-    ;; this by defining `foo-unload-hook'.
+    ;; First off, provide a clean way for package FOO to arrange
+    ;; this by adding hooks on the variable `FOO-unload-hook'.
     (if unload-hook
         (run-hooks unload-hook)
       ;; Otherwise, do our best.  Look through the obarray for symbols
@@ -153,11 +170,11 @@ is nil, raise an error."
                       (consp (symbol-value x))
                       (string-match "-hooks?\\'" (symbol-name x)))
                  (and (boundp x)       ; Known abnormal hooks etc.
-                      (memq x loadhist-hook-functions)))
-            (dolist (y (cdr flist))
+                      (memq x unload-feature-special-hooks)))
+            (dolist (y (cdr unload-hook-features-list))
               (remove-hook x y))))))
     (if (fboundp 'elp-restore-function)        ; remove ELP stuff first
-       (dolist (elt (cdr flist))
+       (dolist (elt (cdr unload-hook-features-list))
          (if (symbolp elt)
              (elp-restore-function elt))))
     (mapc
@@ -182,11 +199,12 @@ is nil, raise an error."
                (fmakunbound x)
                (let ((aload (get x 'autoload)))
                  (if aload (fset x (cons 'autoload aload))))))))
-     (cdr flist))
+     (cdr unload-hook-features-list))
     ;; Delete the load-history element for this file.
     (let ((elt (assoc file load-history)))
       (setq load-history (delq elt load-history)))))
 
 (provide 'loadhist)
 
+;;; arch-tag: 70bb846a-c413-4f01-bf88-78dba4ac0798
 ;;; loadhist.el ends here