[PATCH] * lisp/org.el: (org-get-indirect-buffer) Allow indirect base buffers

[Adam Porter]

Hi,

The attached patch improves the function org-get-indirect-buffer, fixing 
a bug, clarifying the code, and adding a docstring.

Thanks,
AdamFrom 8e70024cae3f4569d6a0c86a0e4d8079126fe9e5 Mon Sep 17 00:00:00 2001
From: Adam Porter <a...@alphapapa.net>
Date: Fri, 4 Nov 2022 14:52:58 -0500
Subject: [PATCH] * lisp/org.el: (org-get-indirect-buffer) Allow indirect base
 buffers

Previously, calling this function on an indirect buffer would fail,
preventing the user from making a new indirect buffer based on an
indirect buffer (e.g. imagine the user makes an indirect buffer for a
large subtree, then wants to make another one for a subtree of that).
Now, the base buffer of the buffer is used, when applicable.

Also, the function is partially rewritten to be clearer, and a
docstring and a FIXME are added.
---
 lisp/org.el | 31 +++++++++++++++++++------------
 1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/lisp/org.el b/lisp/org.el
index d8708f8f2..3b67040f7 100644
--- a/lisp/org.el
+++ b/lisp/org.el
@@ -6160,25 +6160,32 @@ frame is not changed."
     (run-hook-with-args 'org-cycle-hook 'all)
     (and (window-live-p cwin) (select-window cwin))))
 
-(defun org-get-indirect-buffer (&optional buffer heading)
-  (setq buffer (or buffer (current-buffer)))
-  (let ((n 1) (base (buffer-name buffer)) bname)
-    (while (buffer-live-p
-	    (get-buffer
-	     (setq bname
-		   (concat base "-"
-			   (if heading (concat heading "-" (number-to-string n))
-			     (number-to-string n))))))
-      (setq n (1+ n)))
+(cl-defun org-get-indirect-buffer (&optional (buffer (current-buffer)) heading)
+  "Return an indirect buffer based on BUFFER.
+If HEADING, prepend it to the name of the new buffer."
+  (let* ((base-buffer (or (buffer-base-buffer buffer) buffer))
+         (suffix-prefix (if heading
+                            (concat heading "-")
+                          ""))
+         (buffer-name (cl-loop for n from 1 to 100
+                               for suffix = (format "%s%s" suffix-prefix n)
+                               for name = (format "%s-%s"
+                                                  (buffer-name base-buffer)
+                                                  suffix)
+                               while (buffer-live-p (get-buffer name))
+                               finally return name)))
     (condition-case nil
-        (let ((indirect-buffer (make-indirect-buffer buffer bname 'clone)))
+        (let ((indirect-buffer (make-indirect-buffer base-buffer buffer-name 'clone)))
           ;; Decouple folding state.  We need to do it manually since
           ;; `make-indirect-buffer' does not run
           ;; `clone-indirect-buffer-hook'.
           (org-fold-core-decouple-indirect-buffer-folds)
           ;; Return the buffer.
           indirect-buffer)
-      (error (make-indirect-buffer buffer bname)))))
+      ;; FIXME: Explain why this `condition-case' is necessary.  Why
+      ;; could an error be signaled with the CLONE argument non-nil,
+      ;; and why would trying again without CLONE solve the problem?
+      (error (make-indirect-buffer base-buffer buffer-name)))))
 
 (defun org-set-frame-title (title)
   "Set the title of the current frame to the string TITLE."
-- 
2.34.0