From b8c43b594e4e8bf27b1b1c1693d48f07799a1aaf Mon Sep 17 00:00:00 2001
From: Lars Ingebrigtsen <larsi@gnus.org>
Date: Wed, 4 Aug 2021 10:35:53 +0200
Subject: [PATCH] Add a new thing-at-point type: existing-filename

* doc/lispref/text.texi (Buffer Contents): Mention it.

* lisp/thingatpt.el (thing-at-point-file-at-point): New function.
(existing-filename): Register it.
---
 doc/lispref/text.texi |  9 +++++----
 etc/NEWS              |  5 +++++
 lisp/thingatpt.el     | 19 +++++++++++++++----
 3 files changed, 25 insertions(+), 8 deletions(-)

diff --git a/doc/lispref/text.texi b/doc/lispref/text.texi
index e18ba472822..9e0401fffb9 100644
--- a/doc/lispref/text.texi
+++ b/doc/lispref/text.texi
@@ -315,10 +315,11 @@ word on the same line is acceptable.
 @defun thing-at-point thing &optional no-properties
 Return the @var{thing} around or next to point, as a string.
 
-The argument @var{thing} is a symbol which specifies a kind of syntactic
-entity.  Possibilities include @code{symbol}, @code{list}, @code{sexp},
-@code{defun}, @code{filename}, @code{url}, @code{word}, @code{sentence},
-@code{whitespace}, @code{line}, @code{page}, and others.
+The argument @var{thing} is a symbol which specifies a kind of
+syntactic entity.  Possibilities include @code{symbol}, @code{list},
+@code{sexp}, @code{defun}, @code{filename}, @code{existing-filename},
+@code{url}, @code{word}, @code{sentence}, @code{whitespace},
+@code{line}, @code{page}, and others.
 
 When the optional argument @var{no-properties} is non-@code{nil}, this
 function strips text properties from the return value.
diff --git a/etc/NEWS b/etc/NEWS
index 18cca8b4ab3..f0fa686bc9c 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -2639,6 +2639,11 @@ The semantics are as with 'walk-windows'.
 If non-nil, 'find-file-at-point' and friends will try to guess more
 expansively to identify a file name with spaces.
 
++++
+*** New 'thing-at-point' target: 'existing-filename'.
+This is like 'filename', but is a full path, and is nil if the file
+doesn't exist.
+
 ---
 *** Two new commands for centering in 'doc-view-mode'.
 The new commands 'doc-view-center-page-horizontally' (bound to 'c h')
diff --git a/lisp/thingatpt.el b/lisp/thingatpt.el
index 4c2470fbcb6..5bbf1a85b36 100644
--- a/lisp/thingatpt.el
+++ b/lisp/thingatpt.el
@@ -73,8 +73,8 @@ provider functions are called with no parameters at the point in
 question.
 
 \"things\" include `symbol', `list', `sexp', `defun', `filename',
-`url', `email', `uuid', `word', `sentence', `whitespace', `line',
-and `page'.")
+`existing-filename', `url', `email', `uuid', `word', `sentence',
+`whitespace', `line', and `page'.")
 
 ;; Basic movement
 
@@ -156,8 +156,8 @@ positions of the thing found."
   "Return the THING at point.
 THING should be a symbol specifying a type of syntactic entity.
 Possibilities include `symbol', `list', `sexp', `defun',
-`filename', `url', `email', `uuid', `word', `sentence', `whitespace',
-`line', `number', and `page'.
+`filename', `existing-filename', `url', `email', `uuid', `word',
+`sentence', `whitespace', `line', `number', and `page'.
 
 When the optional argument NO-PROPERTIES is non-nil,
 strip text properties from the return value.
@@ -301,6 +301,17 @@ E.g.:
 
 (define-thing-chars filename thing-at-point-file-name-chars)
 
+;; Files
+
+(defun thing-at-point-file-at-point (&optional _lax _bounds)
+  "Return the name of the existing file at point."
+  (when-let ((filename (thing-at-point 'filename)))
+    (setq filename (expand-file-name filename))
+    (and (file-exists-p filename)
+         filename)))
+
+(put 'existing-filename 'thing-at-point 'thing-at-point-file-at-point)
+
 ;;  URIs
 
 (defvar thing-at-point-beginning-of-url-regexp nil
-- 
2.39.2