bug#7756: 24.0.50; enhancements to package.el

[emacs18]

I would like to suggest the following two sets of changes.
The reason for the changes are explained in the diffs.

=== modified file 'lisp/emacs-lisp/package.el'
--- lisp/emacs-lisp/package.el  2010-11-10 21:35:06 +0000
+++ lisp/emacs-lisp/package.el  2010-12-29 18:38:08 +0000
@@ -338,9 +338,14 @@
         (pkg-file (expand-file-name
                    (concat (package-strip-version package) "-pkg")
                    pkg-dir)))
-    (when (and (file-directory-p pkg-dir)
-              (file-exists-p (concat pkg-file ".el")))
-      (load pkg-file nil t))))
+    ;; When one is creating a package and testing it out, it is easy
+    ;; to forget to add the -pkg.el file.  When that happens, it would
+    ;; be useful to provide feedback to the user rather than silently
+    ;; failing.  That is what (error ...) below is for.
+    (when (file-directory-p pkg-dir)
+      (if (file-exists-p (concat pkg-file ".el"))
+          (load pkg-file nil t)
+        (error "'%s' file is missing!")))))
 
 (defun package-load-all-descriptors ()
   "Load descriptors for installed Emacs Lisp packages.
@@ -569,8 +574,16 @@
 (defun package-unpack (name version)
   (let ((pkg-dir (expand-file-name (concat (symbol-name name) "-" version)
                                   package-user-dir)))
+    ;; Delete the package directory if it exists already.  This may
+    ;; not be useful to the end users.  However this is extremely
+    ;; important for package developers as they experiment with which
+    ;; files to include in a package.  If a file is removed from one
+    ;; iteration to the next, then the presence of the unwanted elisp
+    ;; file could cause problems by polluting the generated autoload
+    ;; file.
+    (if (file-directory-p pkg-dir)
+        (delete-directory pkg-dir 'recursive))
     (make-directory package-user-dir t)
-    ;; FIXME: should we delete PKG-DIR if it exists?
     (let* ((default-directory (file-name-as-directory package-user-dir)))
       (package-untar-buffer)
       (package-generate-autoloads (symbol-name name) pkg-dir)