Org uses obsolete `filter-buffer-substring-functions` variable

Org uses obsolete `filter-buffer-substring-functions` variable

[Stefan Kangas]

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Org uses the obsolete variable `filter-buffer-substring-functions'.
This variable is likely due for deletion in Emacs 31.1.

Usually, compatibility code looks for the new way of doing things, and
then prefers that.  But it seems like someone decided here to look for
the old symbol instead, and prefer that.  Unless I'm missing something,
it seems to me that the code for the _new_ variable has been hitherto
unused.

Could you please take a look to confirm that removing
`filter-buffer-substring-functions' from Emacs won't break your code?
I have attached a diff.

Thanks!

[-- Attachment #2: filter-buffer-substring-functions.diff --]
[-- Type: text/x-patch, Size: 2915 bytes --]

diff --git a/lisp/org-agenda.el b/lisp/org-agenda.el
index 6b586899f..ebfccf19e 100644
--- a/lisp/org-agenda.el
+++ b/lisp/org-agenda.el
@@ -2375,14 +2375,8 @@ The following commands are available:
   (add-hook 'post-command-hook #'org-agenda-update-agenda-type nil 'local)
   (add-hook 'pre-command-hook #'org-unhighlight nil 'local)
   ;; Make sure properties are removed when copying text
-  (if (boundp 'filter-buffer-substring-functions)
-      (add-hook 'filter-buffer-substring-functions
-		(lambda (fun start end delete)
-                  (substring-no-properties (funcall fun start end delete)))
-		nil t)
-    ;; Emacs >= 24.4.
-    (add-function :filter-return (local 'filter-buffer-substring-function)
-                  #'substring-no-properties))
+  (add-function :filter-return (local 'filter-buffer-substring-function)
+                #'substring-no-properties)
   (unless org-agenda-keep-modes
     (setq org-agenda-follow-mode org-agenda-start-with-follow-mode
 	  org-agenda-entry-text-mode org-agenda-start-with-entry-text-mode
diff --git a/lisp/org-indent.el b/lisp/org-indent.el
index cabed6acf..a0a0740ee 100644
--- a/lisp/org-indent.el
+++ b/lisp/org-indent.el
@@ -193,15 +193,8 @@ during idle time."
     (when org-indent-mode-turns-on-hiding-stars
       (setq-local org-hide-leading-stars t))
     (org-indent--compute-prefixes)
-    (if (boundp 'filter-buffer-substring-functions)
-	(add-hook 'filter-buffer-substring-functions
-		  (lambda (fun start end delete)
-		    (org-indent-remove-properties-from-string
-		     (funcall fun start end delete)))
-		  nil t)
-      ;; Emacs >= 24.4.
-      (add-function :filter-return (local 'filter-buffer-substring-function)
-		    #'org-indent-remove-properties-from-string))
+    (add-function :filter-return (local 'filter-buffer-substring-function)
+                  #'org-indent-remove-properties-from-string)
     (add-hook 'after-change-functions 'org-indent-refresh-maybe nil 'local)
     (add-hook 'before-change-functions
 	      'org-indent-notify-modified-headline nil 'local)
@@ -224,13 +217,8 @@ during idle time."
       (set-marker org-indent--initial-marker nil))
     (when (local-variable-p 'org-hide-leading-stars)
       (kill-local-variable 'org-hide-leading-stars))
-    (if (boundp 'filter-buffer-substring-functions)
-	(remove-hook 'filter-buffer-substring-functions
-		     (lambda (fun start end delete)
-		       (org-indent-remove-properties-from-string
-			(funcall fun start end delete))))
-      (remove-function (local 'filter-buffer-substring-function)
-		       #'org-indent-remove-properties-from-string))
+    (remove-function (local 'filter-buffer-substring-function)
+                     #'org-indent-remove-properties-from-string)
     (remove-hook 'after-change-functions 'org-indent-refresh-maybe 'local)
     (remove-hook 'before-change-functions
 		 'org-indent-notify-modified-headline 'local)

Re: Org uses obsolete `filter-buffer-substring-functions` variable

[Ihor Radchenko]

Stefan Kangas <stefankangas@gmail.com> writes:

> Org uses the obsolete variable `filter-buffer-substring-functions'.
> This variable is likely due for deletion in Emacs 31.1.
>
> Usually, compatibility code looks for the new way of doing things, and
> then prefers that.  But it seems like someone decided here to look for
> the old symbol instead, and prefer that.  Unless I'm missing something,
> it seems to me that the code for the _new_ variable has been hitherto
> unused.

We backported this change from b1d7e58520dc42a4eda902aa934a250fda6a04ca
Emacs commit.

> Could you please take a look to confirm that removing
> `filter-buffer-substring-functions' from Emacs won't break your code?
> I have attached a diff.

Seems good.
We also do not support Emacs 24 anymore, so the compatibility wrapper is
no longer necessary.

Feel free to either install the change on Emacs side or provide a patch
for me to install on Org side.

-- 
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
or support my work at <https://liberapay.com/yantar92>