[PATCH] ob-tangle.el: restore :tangle closure nil behavior

[Tom Gillespie <tgbugs@gmail.com>]

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Hi,
   Here's a patch to fix the :tangle header behavior when it is
passed a closure that returns nil. Best,
Tom

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From f1e15e0634fffed4648aa11628a14e0a68c3b18d Mon Sep 17 00:00:00 2001
From: Tom Gillespie <tgbugs@gmail.com>
Date: Tue, 15 Aug 2023 13:46:08 -0700
Subject: [PATCH] ob-tangle.el: restore :tangle closure nil behavior

* lisp/ob-tangle.el (org-babel-tangle-collect-blocks):
* lisp/ob-tangle.el (org-babel-tangle--unbracketed-link):
* lisp/ob-tangle.el (org-babel-tangle-single-block): src-tfile fix
case where (cdr (assq :tangle params)) could be nil

This patch restores the original behavior of the :tangle header
argument when a closure returned nil, e.g. #+header: :tangle (or),
by using (or (cdr (assq :tangle params)) "no"). Without this the
call to `file-name-directory' in `org-babel-tangle--unbracketed-link'
can fail with a wrong-type-argument stringp nil error.
---
 lisp/ob-tangle.el | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/lisp/ob-tangle.el b/lisp/ob-tangle.el
index 4566e03ad..0df649d7e 100644
--- a/lisp/ob-tangle.el
+++ b/lisp/ob-tangle.el
@@ -473,14 +473,14 @@ code blocks by target file."
 		  (org-in-archived-heading-p))
 	(let* ((info (org-babel-get-src-block-info 'no-eval))
 	       (src-lang (nth 0 info))
-	       (src-tfile (cdr (assq :tangle (nth 2 info)))))
+	       (src-tfile (or (cdr (assq :tangle (nth 2 info))) "no")))
 	  (unless (or (string= src-tfile "no")
 		      (and tangle-file (not (equal tangle-file src-tfile)))
 		      (and lang-re (not (string-match-p lang-re src-lang))))
 	    ;; Add the spec for this block to blocks under its tangled
 	    ;; file name.
 	    (let* ((block (org-babel-tangle-single-block counter))
-                   (src-tfile (cdr (assq :tangle (nth 4 block))))
+                   (src-tfile (or (cdr (assq :tangle (nth 4 block))) "no"))
 		   (file-name (org-babel-effective-tangled-filename
                                buffer-fn src-lang src-tfile))
 		   (by-fn (assoc file-name blocks)))
@@ -510,7 +510,7 @@ The PARAMS are the 3rd element of the info for the same src block."
               (concat "file:"
                       (file-relative-name (substring bare (match-end 0))
                                           (file-name-directory
-                                           (cdr (assq :tangle params)))))
+                                           (or (cdr (assq :tangle params)) "no"))))
             bare))))))
 
 (defvar org-outline-regexp) ; defined in lisp/org.el
@@ -580,7 +580,7 @@ non-nil, return the full association list to be used by
 			 (match-end 0)
 		       (point-min))))
 	      (point)))))
-         (src-tfile (cdr (assq :tangle params)))
+         (src-tfile (or (cdr (assq :tangle params)) "no"))
 	 (result
 	  (list start-line
 		(if org-babel-tangle-use-relative-file-links
-- 
2.41.0