bug#16202: 24.3.50; lisp-mode's indent-sexp might be buggy (for slime in particular, and lisp in general)

[João Távora]

Hi maintainers,

This was started by bug reports in the slime-devel mailing list

  http://comments.gmane.org/gmane.lisp.slime.devel/11196
  http://comments.gmane.org/gmane.lisp.slime.devel/11189

The reproduction recipe described in these messages requires,
unfortunately, that you install slime.

However, I do think there is a slight bug on emacs's side (which is
probably not visible in emacs-lisp's testing rules). You see, the common
lisp loop macro likes its comments indented like (this is slime's test
nr 11).

   (loop when foo
           do (fubar)
           and collect cash
         else do ;; this is the body of the first else
                 ;; the body is ...
                 (indented to the above comment)
                 (ZMACS gets this wrong)
         do
         when funny-predicate do ;; Here's a comment
                                 (body filled to comment))

and sometimes indent-sexp insists on

   (loop when foo
           do (fubar)
           and collect cash
         else do       ;; this is the body of the first else
                       ;; the body is ...
                 (indented to the above comment)
                 (ZMACS gets this wrong)
         do
         when funny-predicate do ;; Here's a comment
                                 (body filled to comment))

which indented the two comment lines to comment-column, I think. The
patch I attach at the end of this message fixes it.

...as does indenting the sexp with indent-region. This might be naive,
but why not super-simplify indent-sexp to be something like this?

   (defun indent-sexp (&optional endpos)
     (interactive)
     (if endpos
         (indent-region (point) endpos)
       (indent-region (point) (save-excursion
                                (forward-sexp 1)
                                (point)))))

Thanks,
João

*** 
d:/joaot/Vendor/emacs-24.3.5-old/share/emacs/24.3.50/lisp/emacs-lisp/lisp-mode.el
--- #<buffer lisp-mode.el|emacs-24.3.5-old>
***************
*** 1578,1596 ****
        ;; unless a line ends inside a string.
        (while (and (not inner-loop-done)
                    (not (setq outer-loop-done (eobp))))
          (setq state (parse-partial-sexp (point) (progn (end-of-line) (point))
                                          nil nil state))
          (setq next-depth (car state))
!         ;; If the line contains a comment other than the sort
!         ;; that is indented like code,
!         ;; indent it now with indent-for-comment.
!         ;; Comments indented like code are right already.
!         ;; In any case clear the in-comment flag in the state
!         ;; because parse-partial-sexp never sees the newlines.
!         (if (car (nthcdr 4 state))
!             (progn (indent-for-comment)
!                    (end-of-line)
!                    (setcar (nthcdr 4 state) nil)))
          ;; If this line ends inside a string,
          ;; go straight to next line, remaining within the inner loop,
          ;; and turn off the \-flag.
--- 1578,1597 ----
        ;; unless a line ends inside a string.
        (while (and (not inner-loop-done)
                    (not (setq outer-loop-done (eobp))))
+         (setq before-parse (point))
          (setq state (parse-partial-sexp (point) (progn (end-of-line) (point))
                                          nil nil state))
          (setq next-depth (car state))
!         ;; If the line contains nothing but a comment other than the sort that
!         ;; is indented like code, indent it now with indent-for-comment.
!         ;; Comments indented like code are right already.  In any case clear
!         ;; the in-comment flag in the state because parse-partial-sexp never
!         ;; sees the newlines.
!         (when (car (nthcdr 4 state))
!             (when (<= (nth 8 state) before-parse)
!               (indent-for-comment)
!               (end-of-line))
!             (setcar (nthcdr 4 state) nil))
          ;; If this line ends inside a string,
          ;; go straight to next line, remaining within the inner loop,
          ;; and turn off the \-flag.

Diff finished.  Fri Dec 20 13:30:32 2013