(update-file-autoloads): Give clean errors

if autoloads file is empty or can't be written.

1 files changed, 4 insertions, 0 deletions

diff --git a/lisp/emacs-lisp/autoload.el b/lisp/emacs-lisp/autoload.el
index 9ae7188120a..1a85cd7c688 100644
--- a/lisp/emacs-lisp/autoload.el
+++ b/lisp/emacs-lisp/autoload.el
@@ -314,6 +314,10 @@ are used."
                      (expand-file-name generated-autoload-file
                                        (expand-file-name "lisp"
                                                          source-directory)))))
+      (or (> (buffer-size) 0)
+          (error "Autoloads file %s does not exist" buffer-file-name))
+      (or (file-writable-p buffer-file-name)
+          (error "Autoloads file %s is not writable" buffer-file-name))
       (save-excursion
         (save-restriction
           (widen)