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bug#57536: 28.1; filenotify problems on macOS with symbolic links to dir
From: |
Michael Albinus |
Subject: |
bug#57536: 28.1; filenotify problems on macOS with symbolic links to directories |
Date: |
Sun, 04 Sep 2022 13:42:16 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/29.0.50 (gnu/linux) |
Eli Zaretskii <eliz@gnu.org> writes:
Hi,
>> Referencing these commands:
>> ; 1
>> (require 'filenotify)
>>
>> ; 2
>> (defun my-callback (directory)
>> (message (format "called %s" directory)))
>>
>> ; 3
>> (file-notify-add-watch "/private/tmp" '(change attribute-change)
>> 'my-callback)
>>
>> ; 4
>> (file-notify-add-watch "/tmp" '(change attribute-change) 'my-callback)
>>
>> Starting with a fresh emacs -Q, if I execute lines 1, 2, and 3 and then
>> touch a file such as /tmp/OUT, I get the notification as I should.
>>
>> However if I start fresh, execute lines 1, 2, and 4, and touch /tmp/OUT,
>> I do not get a notification.
>>
>> On a Mac, /tmp is a symbolic link to private/tmp (relative path).
>
> I don't see any bug here. If file-notify-add-watch would resolve
> symlinks of its argument, we would be unable to watch changes to the
> symlink file itself.
I agree. Emacs' file notifications are not designed to follow
symlinks. The manual in (info "(elisp) File Notifications") is silent
about, perhaps we shall clarify.
> So if you want to watch changes for the target of a symlink, your Lisp
> program needs to resolve symlinks, e.g. by calling file-truename or
> something similar.
Yep.
>> I first discovered this issue using Helm's find-file and I entered a
>> report with Helm. The Helm developer reports that it works in his case
>> with Linux.
>
> That could be a (mis)feature of our use of inotify, which is used on
> GNU/Linux for implementing file notifications. AFAIU, inotify allows
> control on whether to follow symlinks when setting a watch, and its
> default is to follow symlinks. I think we should call inotify so as
> not to follow symlinks.
Yep. We shall go through our f-n libraries and check the current
behavior, preferred by a new test case. And we shall adjust the
libraries to behave similar.
Will do next days.
Btw, there are bug#16113 and bug#18883, which report a similar problem
in auto-reverting. A possible solution could be to extend the FLAGS arg
of file-notify-add-watch by a condition 'follow', which means to
supervise the expanded symlink instead of the link file itself.
inotify knows the mask bit IN_DONT_FOLLOW (which we haven't set yet),
see inotify(7). Other libraries might offer similar possibilities, which
I haven't checked yet.
Best regards, Michael.
- bug#57536: 28.1; filenotify problems on macOS with symbolic links to directories, Perry Smith, 2022/09/01
- bug#57536: 28.1; filenotify problems on macOS with symbolic links to directories, Eli Zaretskii, 2022/09/02
- bug#57536: 28.1; filenotify problems on macOS with symbolic links to directories,
Michael Albinus <=
- bug#57536: 28.1; filenotify problems on macOS with symbolic links to directories, Eli Zaretskii, 2022/09/04
- bug#57536: 28.1; filenotify problems on macOS with symbolic links to directories, Michael Albinus, 2022/09/04
- bug#57536: 28.1; filenotify problems on macOS with symbolic links to directories, Eli Zaretskii, 2022/09/04
- bug#57536: 28.1; filenotify problems on macOS with symbolic links to directories, Eli Zaretskii, 2022/09/07
- bug#57536: 28.1; filenotify problems on macOS with symbolic links to directories, Michael Albinus, 2022/09/07
- bug#57536: 28.1; filenotify problems on macOS with symbolic links to directories, Michael Albinus, 2022/09/16
- bug#57536: 28.1; filenotify problems on macOS with symbolic links to directories, Eli Zaretskii, 2022/09/16
- bug#57536: 28.1; filenotify problems on macOS with symbolic links to directories, Michael Albinus, 2022/09/16
- bug#57536: 28.1; filenotify problems on macOS with symbolic links to directories, Michael Albinus, 2022/09/17
- bug#57536: 28.1; filenotify problems on macOS with symbolic links to directories, Eli Zaretskii, 2022/09/17