feature/pkg 08bff31081: Prevent accidentally unregistering packages

[Gerd Moellmann]

branch: feature/pkg
commit 08bff310812d8d0821c7b283a2d5e0fdca87f1ca
Author: Gerd Möllmann <gerd@gnu.org>
Commit: Gerd Möllmann <gerd@gnu.org>

    Prevent accidentally unregistering packages
    
    * lisp/emacs-lisp/pkg.el (pkg--remove-from-registry): Check
    for package being eq to a registered package.
---
 lisp/emacs-lisp/pkg.el | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/lisp/emacs-lisp/pkg.el b/lisp/emacs-lisp/pkg.el
index 47317fdf53..56c191f7d0 100644
--- a/lisp/emacs-lisp/pkg.el
+++ b/lisp/emacs-lisp/pkg.el
@@ -161,11 +161,18 @@ Otherwise, NAME must be the name of a registered package."
   (mapc (lambda (name) (puthash name package *package-registry*))
         (package-%nicknames package)))
 
-(defun pkg--remove-from-registry (package)
+(cl-defun pkg--remove-from-registry (package)
   "Remove PACKAGE from the package registry."
-  (remhash (package-%name package) *package-registry*)
-  (mapc (lambda (name) (remhash name *package-registry*))
-        (package-%nicknames package)))
+  ;; Note that an unregistered package might have the same name or
+  ;; nickname as a registered package.  Prevent deleting such a
+  ;; package from unregistering some other package.
+  (let ((names ()))
+    (maphash (lambda (n p)
+               (when (eq p package)
+                 (push n names)))
+             *package-registry*)
+    (dolist (n names)
+      (remhash n *package-registry*))))
 
 (defun pkg--package-or-default (package)
   "Return the package object denoted by PACKAGE.