GNU bug report logs - #21931
25.0.50; behaviour of read-directory-name with double slashes

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Nicolas Richard <youngfrog <at> members.fsf.org>
Subject: bug#21931: closed (Re: bug#21931: 25.0.50; behaviour of
 read-directory-name with double slashes)
Date: Mon, 23 Nov 2015 14:16:02 +0000

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Your bug report

#21931: 25.0.50; behaviour of read-directory-name with double slashes

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 21931 <at> debbugs.gnu.org.

-- 
21931: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=21931
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Nicolas Richard <youngfrog <at> members.fsf.org>
To: John Wiegley <jwiegley <at> gmail.com>
Cc: 21931-done <at> debbugs.gnu.org
Subject: Re: bug#21931: 25.0.50;
 behaviour of read-directory-name with double slashes
Date: Mon, 23 Nov 2015 15:14:59 +0100

John Wiegley writes:
>>>>>> Nicolas Richard <youngfrog <at> members.fsf.org> writes:
>
>> ("/tmp/src/" "/" "src/" "/" "/src/" "/")
>> Is this intended ?
>
> What list were you expecting to see? "//" has always meant "start at root" to
> mean, ignoring whatever comes prior. This is how C-x C-f works, and it means
> you don't have to delete any existing default text in order to begin at root.

Indeed, but when constructing a path via (concat foo "/" bar), it can
happen that the result contains //. If this is then used as arg to
read-directory-name, this leads to an unexpected default.

OTOH (info "(elisp) Directory Names") explicitly says that using concat
for constructing paths in this way is wrong, so I guess that this bug
report is void.

Thanks for looking into it, I close it.

Nico.

[Message part 3 (message/rfc822, inline)]

From: Nicolas Richard <youngfrog <at> members.fsf.org>
To: bug-gnu-emacs <at> gnu.org
Subject: 25.0.50; behaviour of read-directory-name with double slashes
Date: Mon, 16 Nov 2015 07:27:51 +0100

After I eval:
(let ((default-directory "/tmp"))
  (list (read-directory-name "foo" "/tmp/src/")
        (read-directory-name "foo" "/tmp/src//")
        (read-directory-name "foo" "src/")
        (read-directory-name "foo" "src//")
        (read-directory-name "foo" "foo//src/")
        (read-directory-name "foo" "foo//src//")))
and hit RET RET RET RET, I get :
("/tmp/src/" "/" "src/" "/" "/src/" "/")

Is this intended ?

We could normalize the directory name via expand-file-name in all cases,
e.g. :

modified   lisp/files.el
@@ -648,8 +648,7 @@ read-directory-name
   (unless dir
     (setq dir default-directory))
   (read-file-name prompt dir (or default-dirname
-				 (if initial (expand-file-name initial dir)
-				   dir))
+				 (expand-file-name (or initial "") dir))
 		  mustmatch initial
 		  'file-directory-p))

but the docstring states "Value is not expanded---you must call
`expand-file-name' yourself." so I guess the behaviour is important (and
I guess e.g. for tramp).

Should read-file-name be fixed or should the callers make sure to not
use double slashes ?

In GNU Emacs 25.0.50.1 (i686-pc-linux-gnu, X toolkit, Xaw scroll bars)
 of 2015-11-14
Repository revision: ed2e7e20ae0945288c98091f308f5460c3453873
Windowing system distributor 'The X.Org Foundation', version 11.0.11501000
System Description:	Ubuntu 14.04.3 LTS

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