bug#14957: 24.3.50; Flyspell language visible in mode line

[Glenn Morris <rgm@gnu.org>]

Following message was posted via usenet and so does not show up in bug
tracker. I'm not going to mention this issue again.

"Sebastien Vauban" wrote:

> Hello Michael,
>
> Michael Heerdegen wrote:
>>> (add-to-list 'mode-line-format ...)
>>
>> That's not good. `mode-line-format' "automatically becomes
>> buffer-local when set" (see C-h v). Your `add-to-list' only
>> manipulates the `mode-line-format' of the current buffer when your
>> code is evaluated (*scratch*, probably).
>>
>> You have to modify the default value, like this:
>>
>> (setq-default mode-line-format
>> 	      (cons
>> 	       '(:eval
>> 		 (let ((dict (and (featurep 'ispell)
>> 				  (or ispell-local-dictionary
>> 				      ispell-dictionary))))
>> 		   (and dict
>> 			(concat " ["
>> 				(propertize (substring dict 0 2)
>> 					    'face 'mode-line-highlight)
>> 				"]"))))
>> 	       (default-value 'mode-line-format)))
>>
>> Does that help?
>
> It does and did.
>
> Though, when opening some types of files (?) [1], I just observed that there is
> an error message generated:
>
>   ╭────
>   │ File mode specification error: (wrong-type-argument buffer-or-string-p
>   │ (:eval (let ((dict (and (featurep (quote ispell)) (not buffer-read-only)
>   │ (or ispell-local-dictionary ispell-dictionary)))) (and dict (propertize
>   │ (concat " " (substring dict 0 2)) (quote face) (quote
>   │ mode-line-highlight))))))
>   ╰────
>
> I'm not sure what to understand from that... That `mode-line-format' must be
> a string?  Hence, how do we put the `eval' stuff?
>
> Best regards,
>   Seb
>
> [1] Opening a file with a `.csv' extension.