[PATCH] org-eldoc: Fix compatibility with Emacs 28

[Kyle Meyer <kyle@kyleam.com>]

James N. V. Cash writes:

> Kyle Meyer <kyle@kyleam.com> writes:
>
>> Basil L. Contovounesios writes:
>>> How involved would it be to make org-eldoc work in
>>> non-"backwards-compatibility" mode?
>>
>> I think we can do that, while still supporting Org's minimum Emacs
>> version, by following python.el.  Here's what it does:
>> ...
>>
>> ... org-eldoc-documentation-function's signature could be changed to
>> (&rest _ignored), like python-eldoc-function's.
>
> This makes the most sense to me; I missed that the default documentation
> strategy also allows the function to ignore the callback & just return a
> docstring directly.

All right, thanks.  Here's that in patch form.  I briefly tested with
Emacs 26, 27, and 28, and things seemed to work fine (though I'm not an
org-eldoc user).

I'll plan to apply it in a day or two unless there are objections.

-- >8 --
Subject: [PATCH] org-eldoc: Fix compatibility with Emacs 28

* contrib/lisp/org-eldoc.el (org-eldoc-documentation-function): Accept
and ignore additional arguments for compatibility with Emacs 28.
(org-eldoc-load): Use add-function to register
org-eldoc-documentation-function for Emacs versions 25 through 27, as
documented in eldoc-documentation-function.

See Emacs's fd020a2931 (eldoc: modify `eldoc-documentation-function'
using `add-function', 2014-12-05) and c0fcbd2c11 (Expose ElDoc
functions in a hook (Bug#28257), 2020-02-25) for more information on
the Emacs 25 and Emacs 28 changes, respectively.
---
 contrib/lisp/org-eldoc.el | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/contrib/lisp/org-eldoc.el b/contrib/lisp/org-eldoc.el
index 72b10a1fb..b89eb0918 100644
--- a/contrib/lisp/org-eldoc.el
+++ b/contrib/lisp/org-eldoc.el
@@ -127,7 +127,7 @@ (declare-function css-eldoc-function "css-eldoc" ())
 (declare-function php-eldoc-function "php-eldoc" ())
 (declare-function go-eldoc--documentation-function "go-eldoc" ())
 
-(defun org-eldoc-documentation-function ()
+(defun org-eldoc-documentation-function (&rest _ignored)
   "Return breadcrumbs when on a headline, args for src block header-line,
   calls other documentation functions depending on lang when inside src body."
   (or
@@ -161,11 +161,17 @@ (defun org-eldoc-documentation-function ()
 (defun org-eldoc-load ()
   "Set up org-eldoc documentation function."
   (interactive)
-  (if (boundp 'eldoc-documentation-functions)
-      (add-hook 'eldoc-documentation-functions
-		#'org-eldoc-documentation-function nil t)
-    (setq-local eldoc-documentation-function
-		#'org-eldoc-documentation-function)))
+  ;; This approach is taken from python.el.
+  (with-no-warnings
+    (if (null eldoc-documentation-function)
+	;; Emacs<25
+	(setq-local eldoc-documentation-function
+		    #'org-eldoc-documentation-function)
+      (if (boundp 'eldoc-documentation-functions)
+	  (add-hook 'eldoc-documentation-functions
+		    #'org-eldoc-documentation-function nil t)
+	(add-function :before-until (local 'eldoc-documentation-function)
+		      #'org-eldoc-documentation-function)))))
 
 ;;;###autoload
 (add-hook 'org-mode-hook #'org-eldoc-load)

base-commit: e62ca4a1bf576a2c498f47536d3f12cd698e3ac0
-- 
2.27.0