Subject: bug#64733: [PATCH] ; Handle string-at-point at end of buffer gracefully

From: Philip Kaludercic <[email-masked]>
Date: Wed, 19 Jul 2023 18:51:05 +0000

Tags: patch

Evaluating (thing-at-point 'string) at the end of a buffer raises an
error:

--8<---------------cut here---------------start------------->8---
Debugger entered--Lisp error: (wrong-type-argument characterp nil)
  char-syntax(nil)
  (eq (char-syntax (char-after)) 34)
  (if (eq (char-syntax (char-after)) 34) (let ((bound (bounds-of-thing-at-point 'sexp))) (and bound (<= (car bound) (point)) (< (point) (cdr bound)) bound)))
  (if (nth 3 ppss) (condition-case nil (progn (goto-char (nth 8 ppss)) (cons (point) (progn (forward-sexp) (point)))) (error nil)) (if (eq (char-syntax (char-after)) 34) (let ((bound (bounds-of-thing-at-point 'sexp))) (and bound (<= (car bound) (point)) (< (point) (cdr bound)) bound))))
  (let ((ppss (syntax-ppss))) (if (nth 3 ppss) (condition-case nil (progn (goto-char (nth 8 ppss)) (cons (point) (progn (forward-sexp) (point)))) (error nil)) (if (eq (char-syntax (char-after)) 34) (let ((bound (bounds-of-thing-at-point 'sexp))) (and bound (<= (car bound) (point)) (< (point) (cdr bound)) bound)))))
  (save-excursion (let ((ppss (syntax-ppss))) (if (nth 3 ppss) (condition-case nil (progn (goto-char (nth 8 ppss)) (cons (point) (progn (forward-sexp) (point)))) (error nil)) (if (eq (char-syntax (char-after)) 34) (let ((bound (bounds-of-thing-at-point ...))) (and bound (<= (car bound) (point)) (< (point) (cdr bound)) bound))))))
  thing-at-point-bounds-of-string-at-point()
  funcall(thing-at-point-bounds-of-string-at-point)
  (cond ((get thing 'bounds-of-thing-at-point) (funcall (get thing 'bounds-of-thing-at-point))) ((and (not (eq thing 'whitespace)) (save-excursion (goto-char (point-min)) (not (re-search-forward "[^\11\n ]" nil t)))) nil) (t (let ((orig (point))) (condition-case nil (progn (save-excursion (funcall (or ... ...)) (funcall (or ... ...)) (let (...) (if ... ... ... ... ... ...)))) (error nil)))))
  bounds-of-thing-at-point(string)
  (let ((bounds (bounds-of-thing-at-point thing))) (if bounds (progn (buffer-substring (car bounds) (cdr bounds)))))
  (cond ((let* ((--cl-var-- thing-at-point-provider-alist) #'nil (pthing nil) (result nil) (--cl-var-- t) (--cl-var-- t) --cl-var--) (while (and (consp --cl-var--) (progn (progn (setq function ...) (setq pthing ...)) (if (eq pthing thing) (progn ...)) (if result (progn ... ...) t))) (setq --cl-var-- (cdr --cl-var--)) (setq --cl-var-- nil)) --cl-var--)) ((get thing 'thing-at-point) (funcall (get thing 'thing-at-point))) (t (let ((bounds (bounds-of-thing-at-point thing))) (if bounds (progn (buffer-substring (car bounds) (cdr bounds)))))))
  (let ((text (cond ((let* ((--cl-var-- thing-at-point-provider-alist) #'nil (pthing nil) (result nil) (--cl-var-- t) (--cl-var-- t) --cl-var--) (while (and ... ...) (setq --cl-var-- ...) (setq --cl-var-- nil)) --cl-var--)) ((get thing 'thing-at-point) (funcall (get thing 'thing-at-point))) (t (let ((bounds ...)) (if bounds (progn ...))))))) (if (and text no-properties (sequencep text)) (progn (set-text-properties 0 (length text) nil text))) text)
  thing-at-point(string)
  eval-expression((thing-at-point 'string) nil nil 127)
  funcall-interactively(eval-expression (thing-at-point 'string) nil nil 127)
  command-execute(eval-expression)
--8<---------------cut here---------------end--------------->8---

In this case it is easy to avoid it, with the below patch, by ensuring
that `char-syntax' is not passed a nil.

In GNU Emacs 29.0.92 (build 1, x86_64-pc-linux-gnu, GTK+ Version
 3.24.37, cairo version 1.16.0) of 2023-07-16 built on quetzal
Repository revision: fcde115d5748880ad7ebbf43a10753fb7014a6e1
Repository branch: emacs-29
System Description: Debian GNU/Linux 12 (bookworm)

Configured using:
 'configure --with-pgtk --with-native-compilation --with-imagemagick
 --with-tree-sitter'

>From fb5da3b4a4785938d82c8ce4ea59215a8905ddd7 Mon Sep 17 00:00:00 2001
From: Philip Kaludercic <[email-masked]>
Date: Wed, 19 Jul 2023 20:49:30 +0200
Subject: [PATCH] ; Handle string-at-point at end of buffer gracefully

* lisp/thingatpt.el (thing-at-point-bounds-of-string-at-point): Check
if 'char-after' returns non-nil before passing it to 'char-syntax'.
---
 lisp/thingatpt.el | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lisp/thingatpt.el b/lisp/thingatpt.el
index 9363a474cb5..46e700c2091 100644
--- a/lisp/thingatpt.el
+++ b/lisp/thingatpt.el
@@ -250,7 +250,7 @@ thing-at-point-bounds-of-string-at-point
             (goto-char (nth 8 ppss))
             (cons (point) (progn (forward-sexp) (point))))
         ;; At the beginning of the string
-        (if (eq (char-syntax (char-after)) ?\")
+        (if (and (char-after) (eq (char-syntax (char-after)) ?\"))
             (let ((bound (bounds-of-thing-at-point 'sexp)))
 	      (and bound
 	           (<= (car bound) (point)) (< (point) (cdr bound))
-- 
2.39.2