Re: c47b535bb origin/main org-element: Remove dependency on ‘org-emphasis-regexp-components’

[Max Nikulin <manikulin@gmail.com>]

On 21/11/2021 17:01, Ihor Radchenko wrote:
> Max Nikulin writes:
> 
>> My draft version is attached. Ihor, thank you for inspiration. Feel free
>> to improve it. I hope, it makes problem more apparent to user who tries
>> to customize markers. Have I missed some undesired side effects?
> 
>> Unfortunately with "set" type in defcustom "catch inappropriate" item is
>> not hidden for valid configuration.
 >
> I am not very familiar with :set customisation. Could you elaborate what
> you mean? I do not understand what "catch inappropriate" refers to.

I am afraid of confusion of ":set" defcustom parameter and "set" type in 
":type" parameter.

I mean "set" instead of "repeat" (or "list" in your patch). It is 
collection of *unique* items. Other variants allow to add several 
entries for the same marker, e.g. "*". Set does not allow users to add 
duplicated entries. I started from your description of allowed entries
and changed rigid "list" type to "set" and added (approximately)

           (list :tag "Unsupported ignored"
	   (string :tag "Marker")
	   (choice :tag "Font"
	    (face :tag "Face")
	    (plist :tag "Property list"))
	   (option (const verbatim))

to notify user that some part of configuration does not work, it is 
always shown in `customize-variable' interface, even as a disabled 
option for default configuration.

With repeat, "Unsupported" options are not present in customization 
buffer, unless user has something like

(custom-set-variables
   '(org-emphasis-alist
      (quote
        (
	("*" bold)
	("_" underline)
	("=" org-verbatim verbatim)
	("/" italic)
	("~" org-code verbatim)
	("!" org-todo) ;; does not work
	("+" (:strike-through t)))))
   )

It is possible to add "seq" entry to catch list entries having 
completely invalid structure, but I decided that it is redundant.

So with "repeat" type user may notice "Unsupported ignored" option in 
customization interface. I think, it is not enough, so I added ":set" 
function that issues a warning during load time. Invalid configuration 
may still remain hidden in the case of `setq' instead of 
`custom-set-variables' in the init file or `eval-after-load' hook. I am 
afraid, nothing could be done to reliably detect the last case.

>> + ... It is possible to customize
>> +~org-emphasis-alist~ variable, but it will be deprecated.
> 
> We probably do not need to mention to-be-deprecated variables in manual.
> It will only confuse users.

I do not insist. My intention is to inform users that wide spread 
recipes should be avoided.

> Maybe we should also take a chance and deprecate org-emphasis-alist now?
> We can introduce org-bold/italics/... faces and use them in
> org-emphasis-alist default value.

I do not mind. I have never experimented with themes, so I would leave 
this part of work to someone else.