bug#37611: [PATCH] Default FILE to the current buffer for list-tags

[Hong Xu <hong@topbug.net>]

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On 10/4/19 12:41 PM, Eli Zaretskii wrote:
>> Cc: 37611@debbugs.gnu.org
>> From: Hong Xu <hong@topbug.net>
>> Date: Fri, 4 Oct 2019 12:20:46 -0700
>>
>>> Did you try this in the Emacs source tree?  We use the TAGS 'include'
>>> facility to include various TAGS files in a single master file.  This
>>> seems to get in the way when you invoke this command from a Lisp file,
>>> because list-tags only recognizes one of the C source files as
>>> completion candidates.  What does this do with your changes?
>>>
>>
>> I tried in the Emacs source tree without problem (I ran universal ctags, "ctags -R -e ." from root of the source tree). How do you generate the TAGS file? Is there any instruction? I can take a look at it.
> 
> I use "make TAGS", of course.
> 


I updated the patch (as attached) so that it now works with the TAGS generated using `make TAGS` and also includes missing updates to docstring and info nodes.

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From a806553186635aeb0e7763490e41b0ac68e602c4 Mon Sep 17 00:00:00 2001
From: Hong Xu <hong@topbug.net>
Date: Thu, 3 Oct 2019 16:36:54 -0700
Subject: [PATCH] Default FILE to the current buffer for list-tags

* lisp/progmodes/etags.el (list-tags)
(tags--get-current-buffer-name-in-tags-file): Default FILE to the
current buffer for list-tags.

* doc/emacs/maintaining.texi (List Identifiers): Update `list-tags' doc.
---
 doc/emacs/maintaining.texi |  4 +++-
 lisp/progmodes/etags.el    | 25 +++++++++++++++++++------
 2 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/doc/emacs/maintaining.texi b/doc/emacs/maintaining.texi
index 9a9957069fd6..519667dfbe92 100644
--- a/doc/emacs/maintaining.texi
+++ b/doc/emacs/maintaining.texi
@@ -2124,7 +2124,9 @@ List Identifiers
 file.  Do not include a directory as part of the file name unless the
 file name recorded in the tags table includes a directory.  This
 command works only with the etags backend, and requires a tags table
-for the project to be available.  @xref{Tags Tables}.
+for the project to be available.  @xref{Tags Tables}.  If used
+interactively, the default tag is file name of the current buffer if
+used interactively.
 
 @c Sadly, the new-and-improved Xref feature doesn't provide anything
 @c close to the described below features of the now-obsoleted
diff --git a/lisp/progmodes/etags.el b/lisp/progmodes/etags.el
index a03516100087..5edced5080e2 100644
--- a/lisp/progmodes/etags.el
+++ b/lisp/progmodes/etags.el
@@ -1852,15 +1852,28 @@ tags-complete-tags-table-file
 	(all-completions string (tags-table-files) predicate)
       (try-completion string (tags-table-files) predicate))))
 
+(defun tags--get-current-buffer-name-in-tags-file ()
+  "Get the file name that the current buffer corresponds in the tags file."
+  (let ((tag-dir
+         (save-excursion
+           (visit-tags-table-buffer)
+           (file-name-directory (buffer-file-name)))))
+    (file-relative-name (buffer-file-name) tag-dir)))
+
 ;;;###autoload
 (defun list-tags (file &optional _next-match)
   "Display list of tags in file FILE.
-This searches only the first table in the list, and no included tables.
-FILE should be as it appeared in the `etags' command, usually without a
-directory specification."
-  (interactive (list (completing-read "List tags in file: "
-				      'tags-complete-tags-table-file
-				      nil t nil)))
+This searches only the first table in the list, and no included
+tables.  FILE should be as it appeared in the `etags' command,
+usually without a directory specification.  If called
+interactively, FILE defaults to the file name of the current
+buffer."
+  (interactive (list (completing-read
+                      "List tags in file: "
+                      'tags-complete-tags-table-file
+                      nil t
+                      ;; Default FILE to the current buffer.
+                      (tags--get-current-buffer-name-in-tags-file))))
   (with-output-to-temp-buffer "*Tags List*"
     (princ (substitute-command-keys "Tags in file `"))
     (tags-with-face 'highlight (princ file))
-- 
2.20.1