bug#5937: 23.1.95; why saving empty abbrev tables

[Leo <sdl.web@gmail.com>]

Why empty abbrev tables are saved to file? It seems to make it more
difficult for editing (edit-abbrevs) because the buffer is full of empty
abbrev. I wonder if saving only non-empty tables is better and user
friendlier. For example, any harm of doing something like this:

(defun abbrev-table-empty-p (table)
  "Return nil if there are no abbrev symbols in abbrev table object TABLE."
  (unless (abbrev-table-p table)
    (error "Non abbrev table object"))
  (not (catch 'some
         (mapatoms (lambda (sym)
                     (when (abbrev-symbol (symbol-name sym) table)
                       (throw 'some t)))
                   table))))
(defadvice write-abbrev-file (around nonempty-abbrev-tables activate)
  "Ignore empty abbrev tables when writing to FILE."
  (let ((file (ad-get-arg 0))
        (coding-system-for-write 'emacs-mule)
        (tables (loop for table in abbrev-table-name-list
                      unless (abbrev-table-empty-p (symbol-value table))
                      collect table)))
    (or (and file (> (length file) 0)) (setq file abbrev-file-name))
    (with-temp-file file
      (insert ";;-*-coding: emacs-mule;-*-\n")
      (dolist (table (sort tables
                           (lambda (s1 s2)
                             (string< (symbol-name s1)
                                      (symbol-name s2)))))
        (insert-abbrev-table-description table nil)))))