bug#24627: 24.5; (thing-at-point 'list) may return a non-empty string without a list

[Tino Calancha <tino.calancha@gmail.com>]

Andreas Röhler <andreas.roehler@easy-emacs.de> writes:

> With
>
> (defun foo ())
>
> at first open paren
>
> M-: (thing-at-point 'list t) RET
>
> returns the whole thing, right.
>
> But at second open paren returns the whole function too - where it
> should return the empty arg-list

Following patch do the right thing in my example and your example.
Feel free to check it with some other examples that you may have:

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From dc2703a43a7b5dae60f7e88805971472253d4600 Mon Sep 17 00:00:00 2001
From: Tino Calancha <tino.calancha@gmail.com>
Date: Wed, 12 Oct 2016 01:16:52 +0900
Subject: [PATCH] (thing-at-point 'list) return nil if no list at point

* lisp/thingatpt.el (thing-at-point-bounds-of-list-at-point):
Check first if we are at the beginning of a top-level sexp (Bug#24627).
Escape '[' and ']' in doc string.
---
 lisp/thingatpt.el | 22 +++++++++-------------
 1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/lisp/thingatpt.el b/lisp/thingatpt.el
index 6d1014b..acacff2 100644
--- a/lisp/thingatpt.el
+++ b/lisp/thingatpt.el
@@ -219,22 +219,18 @@ 'beginning-of-sexp
 
 (defun thing-at-point-bounds-of-list-at-point ()
   "Return the bounds of the list at point.
-[Internal function used by `bounds-of-thing-at-point'.]"
+\[Internal function used by `bounds-of-thing-at-point'.\]"
   (save-excursion
     (let ((opoint (point))
-	  (beg (ignore-errors
-		 (up-list -1)
-		 (point))))
+          (beg (if (looking-at-p "(")
+                   (point)
+                 (ignore-errors
+                   (up-list -1)
+                   (point)))))
       (ignore-errors
-	(if beg
-	    (progn (forward-sexp)
-		   (cons beg (point)))
-	  ;; Are we are at the beginning of a top-level sexp?
-	  (forward-sexp)
-	  (let ((end (point)))
-	    (backward-sexp)
-	    (if (>= opoint (point))
-		(cons opoint end))))))))
+        (when beg
+          (forward-sexp)
+          (cons beg (point)))))))
 
 ;; Defuns
 
-- 
2.9.3

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In GNU Emacs 26.0.50.1 (x86_64-pc-linux-gnu, GTK+ Version 3.22.1)
 of 2016-10-11
Repository revision: 9640e9f4e95cd95c04875e90a4ff638e1e51f977