[PATCH] Fix `org-babel-detangle' handling of false positives

[Kevin Foley <kevin@kevinjfoley.me>]

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This patch fixes the way `org-babel-detangle' handles false positive
matches for links.  Without the patch it tries to use match data that
may not be present in a false positive.  I've also included a regression
test.

This is my first contribution to Org Mode or Emacs and my first patch
by mailing list so please let me know if I've overlooked anything.

Also note I have not assigned copyright to FSF at this time, however I
believe this change should be small enough to not require it.

Kevin Foley


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From 82e2d108536101c5a5ff9f8a0009051e5a308a3a Mon Sep 17 00:00:00 2001
From: "Kevin J. Foley" <kevin@kevinjfoley.me>
Date: Tue, 28 Jan 2020 17:51:29 -0500
Subject: [PATCH] Fix `org-babel-detangle' handling of false positives

* lisp/ob-tangle.el (org-babel-detangle): Handle false positive
matches of `org-link-bracket-re'

* testing/examples/babel.el: New file for babel detangle false
positive test

* testing/examples/babel.org (detangle): Add detangle/false positive
example

* testing/lisp/test-ob-tangle.el (ob-tangle/detangle-false-positive):
Add test for detangle false positive

TINYCHANGE
---
 lisp/ob-tangle.el              | 18 ++++++++++--------
 testing/examples/babel.el      |  5 +++++
 testing/examples/babel.org     | 13 +++++++++++++
 testing/lisp/test-ob-tangle.el | 11 +++++++++++
 4 files changed, 39 insertions(+), 8 deletions(-)
 create mode 100644 testing/examples/babel.el

diff --git a/lisp/ob-tangle.el b/lisp/ob-tangle.el
index 946039869..4dac0f786 100644
--- a/lisp/ob-tangle.el
+++ b/lisp/ob-tangle.el
@@ -513,14 +513,16 @@ (defun org-babel-detangle (&optional source-code-file)
     (goto-char (point-min))
     (let ((counter 0) new-body end)
       (while (re-search-forward org-link-bracket-re nil t)
-        (when (re-search-forward
-	       (concat " " (regexp-quote (match-string 2)) " ends here"))
-          (setq end (match-end 0))
-          (forward-line -1)
-          (save-excursion
-	    (when (setq new-body (org-babel-tangle-jump-to-org))
-	      (org-babel-update-block-body new-body)))
-          (setq counter (+ 1 counter)))
+        (if (and (match-string 2)
+		 (re-search-forward
+		  (concat " " (regexp-quote (match-string 2)) " ends here") nil t))
+	    (progn (setq end (match-end 0))
+		   (forward-line -1)
+		   (save-excursion
+		     (when (setq new-body (org-babel-tangle-jump-to-org))
+		       (org-babel-update-block-body new-body)))
+		   (setq counter (+ 1 counter)))
+	  (setq end (point)))
         (goto-char end))
       (prog1 counter (message "Detangled %d code blocks" counter)))))

diff --git a/testing/examples/babel.el b/testing/examples/babel.el
new file mode 100644
index 000000000..a7bb0ccf5
--- /dev/null
+++ b/testing/examples/babel.el
@@ -0,0 +1,5 @@
+(string-match-p "^#[[:digit:]]+$" "#123")
+
+;; [[id:73115FB0-6565-442B-BB95-50195A499EF4][detangle:1]]
+;; detangle changes
+;; linked content to detangle:1 ends here
diff --git a/testing/examples/babel.org b/testing/examples/babel.org
index c889d5d92..b0942800a 100644
--- a/testing/examples/babel.org
+++ b/testing/examples/babel.org
@@ -488,3 +488,16 @@ nil
 #+BEGIN_SRC emacs-lisp :output-dir xxx :file foo.bar
 nil
 #+END_SRC
+* detangle
+** false positive
+The =[[= causes a false positive which ~org-babel-detangle~ should handle properly
+#+begin_src emacs-lisp :tangle yes
+(string-match-p "^#[[:digit:]]+$" "#123")
+#+end_src
+** linked content to detangle
+:PROPERTIES:
+:ID:       73115FB0-6565-442B-BB95-50195A499EF4
+:END:
+#+begin_src emacs-lisp :tangle yes :comments link
+  ;; detangle
+#+end_src
diff --git a/testing/lisp/test-ob-tangle.el b/testing/lisp/test-ob-tangle.el
index 301f7aff7..ed75e6ca4 100644
--- a/testing/lisp/test-ob-tangle.el
+++ b/testing/lisp/test-ob-tangle.el
@@ -25,6 +25,8 @@
 \f
 ;;; Code:

+(require 'subr-x)
+
 ;; TODO
 ;; (ert-deftest ob-tangle/noweb-on-tangle ()
 ;;   "Noweb header arguments tangle correctly.
@@ -380,6 +382,15 @@ (ert-deftest ob-tangle/commented-src-blocks ()
 		    (org-split-string (buffer-string))))
 	      (delete-file file))))))

+(ert-deftest ob-tangle/detangle-false-positive ()
+  "Test handling of false positive link during detangle."
+  (org-test-in-example-file (expand-file-name "babel.el" org-test-example-dir)
+    (org-babel-detangle)
+    (org-test-at-id "73115FB0-6565-442B-BB95-50195A499EF4"
+    (org-babel-next-src-block)
+    (should (equal (string-trim (org-element-property :value (org-element-at-point)))
+		   ";; detangle changes")))))
+
 (provide 'test-ob-tangle)

 ;;; test-ob-tangle.el ends here
--
2.19.0