Re: Error in post-command-hook (completion-in-region--postch): (wrong-type-argument stringp nil)

[Stefan Monnier <monnier@iro.umontreal.ca>]

> (defun nrepl-complete-at-point ()
>   (interactive)
>   (let ((sap (symbol-at-point)))
>     (when (and sap (not (in-string-p)))
>       (nrepl-send-string "(require 'complete.core)" "user" 'identity)
>       (let ((form (format "(complete.core/completions \"%s\" *ns*)" sap))
> 	    (bounds (bounds-of-thing-at-point 'symbol)))
> 	(let ((completions (car (read-from-string
> 				 (plist-get (nrepl-send-string-sync form nrepl-buffer-ns)
> 					    :value)))))
> 	  (when completions
> 	    ;; TODO: Remove me again!
> 	    (assert (null (remove-if 'stringp completions)))
> 	    (list (car bounds) (cdr bounds) completions)))))))

The completion-in-region-mod calls to completion-at-point-functions
don't care much about the "completions" part of the triplet you return,
so the nrepl-send-string* are a complete waste.
Same for potentially other cases such as when auto-complete calls
completion-at-point-functions to try and decide whether or not there's
potentially something to complete at point.

IOW, nrepl-complete-at-point should return something more like
(guaranteed 100% untested):

   (defun nrepl-complete-at-point ()
     (interactive)
     (let ((sap (symbol-at-point)))
       (when (and sap (not (in-string-p)))
         (let ((bounds (bounds-of-thing-at-point 'symbol)))
   	   (list (car bounds) (cdr bounds)
                 (completion-table-dynamic
                  (lambda (str)
                    (nrepl-send-string "(require 'complete.core)"
                                       "user" 'identity)
                    (let ((form (format "(complete.core/completions \"%s\" *ns*)" str)))
                      (car (read-from-string
			    (plist-get (nrepl-send-string-sync
                                        form nrepl-buffer-ns)
				       :value)))))))))))


-- Stefan