[PATCH] ob-tangle: Add flag to optionally remove files before writing

[Olivier Lischer <olivier.lischer@liolin.ch>]

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In December last year was a change introduced, that a file should not be
removed before
tangling (https://lists.gnu.org/r/emacs-orgmode/2021-05/msg00337.html).
In an older bug report
(https://lists.gnu.org/r/emacs-orgmode/2021-05/msg00337.html)
the decision was to remove the file before writing.
I added a variable to switch between both behaviors.

Any feedback or advice is welcome.


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From 4f2f2a0dcca82a934144636da478a9243e514f66 Mon Sep 17 00:00:00 2001
From: Olivier Lischer <olivier.lischer@liolin.ch>
Date: Tue, 23 Jan 2024 21:02:20 +0100
Subject: [PATCH] ob-tangle: Add flag to optionally remove files before writing

* lisp/ob-tangle.el: Add variable
`org-babel-tangle-remove-file-before-write'.
(org-babel-tangle): Remove file before writing when
`org-babel-tangle-remove-file-before-write' is set.

The variable `org-babel-tangle-remove-file-before-write' adds support
for the current and old behaviour of `org-babel-tangle'.

TINYCHANGE
---
 etc/ORG-NEWS      |  4 ++++
 lisp/ob-tangle.el | 12 +++++++++---
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/etc/ORG-NEWS b/etc/ORG-NEWS
index f537486d4..c7c3ee264 100644
--- a/etc/ORG-NEWS
+++ b/etc/ORG-NEWS
@@ -800,6 +800,10 @@ Completion is enabled for links to man pages added using ~org-insert-link~:
 =C-c C-l man RET emacscl TAB= to get =emacsclient=.  Of course, the ~ol-man~
 library should be loaded first.
 
+*** =ob-tangle.el=: Add flag to optionally remove files before writing
+
+When ~org-babel-tangle-remove-file-before-write~ is set to ~t~ the file is removed before writing.
+
 ** New functions and changes in function arguments
 *** New API functions to store data within ~org-element-cache~
 
diff --git a/lisp/ob-tangle.el b/lisp/ob-tangle.el
index 72089a9a5..37fcd194c 100644
--- a/lisp/ob-tangle.el
+++ b/lisp/ob-tangle.el
@@ -166,6 +166,12 @@ read-write permissions for the user, read-only for everyone else."
   :package-version '(Org . "9.6")
   :type 'integer)
 
+(defcustom org-babel-tangle-remove-file-before-write nil
+  "Prevents the deletion of an existing file before tangle"
+  :group 'org-babel-tangle
+  :package-version '(Org . "9.7")
+  :type 'boolean)
+
 (defun org-babel-find-file-noselect-refresh (file)
   "Find file ensuring that the latest changes on disk are
 represented in the file."
@@ -313,9 +319,9 @@ matching a regular expression."
                                       (compare-buffer-substrings
                                        nil nil nil
                                        tangle-buf nil nil)))))))
-                     ;; We do not erase, but overwrite previous file
-                     ;; to preserve any existing symlinks.
-		     (write-region nil nil file-name)
+                     (when (and (file-exists-p file-name) org-babel-tangle-remove-file-before-write)
+                       (delete-file file-name))
+                     (write-region nil nil file-name)
 		     (mapc (lambda (mode) (set-file-modes file-name mode)) modes))
                    (push file-name path-collector))))))
 	 (if (equal arg '(4))
-- 
2.43.0