bug#81295: 32.0.50; dired-auto-toggle-b-switch problem with subdirectory

On 26/07/2026 18:05 +0200, Stephen Berman wrote:

> On Mon, 20 Jul 2026 17:14:38 +0300 Filipp Gunbin <[email protected]> wrote:
>
>> On 18/07/2026 12:01 +0200, Stephen Berman wrote:
>>
>>> On Sat, 18 Jul 2026 03:22:22 +0300 Filipp Gunbin <[email protected]> wrote:
>>>
>>>> On 17/07/2026 16:08 +0200, Stephen Berman wrote:
>>>>
>>>> [...]
>>>>
>>>>> - Typing `C-u i RET' calls `dired-maybe-insert-subdir' with argument
>>>>>   SWITCHES set to the default value "-al".  This gets passed to
>>>>>   `dired-insert-subdir', which in turn passes it to
>>>>>   `dired-insert-subdir-validate', which return `(t t)' because neither
>>>>>   SWITCHES nor `dired-actual-switches' includes either the "F" or "b"
>>>>>   switch.  Hence, directory 2 gets inserted as a subdir.  Before
>>>>>   `dired-insert-subdir' returns, the value of SWITCHES gets added to
>>>>>   `dired-switches-alist'.
>>>>>
>>>>> - When `dired-insert-subdir' returns, `dired--toggle-b-switch' gets
>>>>>   called from `post-command-hook' (since `dired-auto-toggle-b-switch' is
>>>>>   t), and since directory 2 contains a file name with a newline
>>>>>   `(dired--filename-with-newline-p)' returns t, and this results in the
>>>>>   "b" switch getting added to `dired-actual-switches' and then
>>>>>   `dired-revert' is called.
>>>>
>>>> I think the problem is that dired--toggle-b-switch only modifies
>>>> dired-actual-switches, while it should also modify dired-switches-alist.
>>>> Otherwise they go out of sync, may conflict, and lead to problematic
>>>> cases like this.
>>>>
>>>> From your description it looks like that would naturally solve the
>>>> current problem.
>>>
>>> I don't see a way to make `dired--toggle-b-switch' modify
>>> `dired-switches-alist' that isn't much more complex than the solution I
>>> proposed in patch 1.  If you do, can you post a patch?
>>
>> Alas, currently I don't have enough time, maybe later.  I've tried to
>> explain my thoughts in more detail below.
>>
>>>> But it would also mean that any switches that user enters in C-u i
>>>> should be modified with respect to dired-auto-toggle-b-switch.  It's
>>>> "auto-toggle", after all.
>>>
>>> Right, that's what patch 1 does.
>>
>> I don't like this change:
>>
>> -    (and (not switches) cons (setq switches (cdr cons)))
>> +    (and (not switches) (not (dired-switches-escape-p dired-actual-switches))
>> +         cons (setq switches (cdr cons)))
>>
>> because it makes a non-obvious special case.  Currently it is: unless
>> the switches are specified, take them from dired-switches-alist.  The
>> patch makes an exclusion, a non-obvious one.
>>
>> The very fact that you're trying to escape validation doesn't make it
>> better either: the validation is there for a reason, right?
>
> The validation is to prevent the situation where the Dired buffer uses
> one or both of the -b or -F switches while the inserted subdirs do not,
> or vice versa.  Your case demonstrates that validation is problematic
> precisely when the -b switch gets added by dired--toggle-b-switch, so
> circumventing validation in this case is a simple and effective way of
> avoiding the problem, given the current handling of file names with
> newlines.  No doubt a more intuitively appealing solution is possible,
> but my impression is it would require fairly involved changes in the
> current handling of file names with newlines.

I think the constraints which validation imposes are reasonable, so I
wouldn't want to circumvent it here.  Letting different combinations of
-b/-F now will make it harder to do things "the right way" later.

That said, I don't know the exact reasons why the validations were added
originally.  But we should either keep them (and don't try to
circumvent), or remove them altogether.

>>>> And this brings one more thing.  It seems like you use
>>>> dired-listing-switches as "the original" switches, for example in
>>>> dired-internal-noselect:
>>>>
>>>>     (unless (or dired-auto-toggle-b-switch
>>>>                 (dired-switches-escape-p dired-listing-switches)
>>>>                 (dired-switches-escape-p dired-actual-switches))
>>>>
>>>> But C-u C-x d will ask you for your custom switches, and
>>>> dired-listing-switches is only initial input there.  There's also code
>>>> in dired--toggle-b-switch which uses dired-listing-switches in this way:
>>>>
>>>>       (unless (dired-switches-escape-p dired-listing-switches)
>>>>         (when (dired-switches-escape-p dired-actual-switches)
>>>>           (setq dired-actual-switches (dired--remove-b-switch))
>>>>           (dired-revert))))))
>>>>
>>>> Perhaps we should have buffer-local variables which record the initial
>>>> top-level and subdirectory switches, and consult them when deciding what
>>>> to do in dired--toggle-b-switch.
>>>
>>> I don't follow you here; AFAIU the user option `dired-listing-switches'
>>> can be overriden by `C-u C-x d', and the resulting switches are then the
>>> value of `dired-actual-switches', otherwise, `dired-listing-switches'
>>> and `dired-actual-switches' have the same value (unless something like
>>> `dired--toggle-b-switch' changes the latter).  Can you elaborate on what
>>> you're proposing (or considering) for `dired--toggle-b-switch'?
>>
>> "Then" branch currently adds the "-b" switch when we have newlines in
>> files, and when the user option is enabled:
>>
>>     (if (and (dired--filename-with-newline-p) dired-auto-toggle-b-switch)
>>         (unless (dired-switches-escape-p dired-actual-switches)
>>           (setq dired-actual-switches (concat dired-actual-switches " -b"))
>>           (dired-revert))
>>
>> But the logic in "else" branch is, I think, incomplete.
>>
>> Here we're checking that user hasn't specified -b explicitly by testing
>> dired-listing-switches, and this doesn't account for the case of C-u C-x
>> d, because dired-listing-switches then have nothing to do with the
>> user's choice:
>>
>>       (unless (dired-switches-escape-p dired-listing-switches)
>>         (when (dired-switches-escape-p dired-actual-switches)
>>           (setq dired-actual-switches (dired--remove-b-switch))
>>           (dired-revert))))))
>>
>> So I was thinking what the root cause of the problem is, and it appeared
>> to me that we don't have enough variables currently:
>>
>> Top-level switches:
>>
>> (1) defcustom for default switches - dired-listing-switches
>>
>> (2) The value that user actually entered dired with: missing
>
> You mean with `C-u C-x d', right?

Yes.

> That value is assigned to dired-actual-switches in dired-mode:
>
> (setq-local dired-actual-switches
>             (or switches (connection-local-value dired-listing-switches)))

But with dired-auto-toggle-b-switch feature dired-actual-switches may be
modified, and so we lose information about whether the user explicitly
specified -b or not.  That's why I separated (2) and (3).

>> (3) The value of actual ls invocation: dired-actual-switches
>
> As the code snippet from dired-mode shows, this is either (1) or (2).

See above.

>> Subdir switches:
>>
>> (4) defcustom for default switches - (or dired-subdir-switches
>> dired-listing-switches)
>>
>> (5) The value that user actually entered dired with, per subdir:
>> dired-subdir-switches alist
>>
>> (6) The value of actual ls invocation, per subdir: missing
>
> Here, too, it's dired-actual-switches, let-bound in
> dired-insert-subdir-doinsert:
>
>       (let ((dired-actual-switches
> 	     (or switches
> 		 dired-subdir-switches
> 		 (string-replace "R" "" dired-actual-switches))))

This defaults to (adjusted) dired-actual-switches, yes, but otherwise
the same reasoning as above applies.  The caller of this function,
dired-insert-subdir, uses dired-switches-alist to store specific
switches per subdir (5).

>> The validation currently ensures that either all directories in dired
>> have -b, or none.  In the current problematic case, we end up with:
>>
>> - "-alb" in dired-actual-switches.  This value is ok.
>>
>> - "-al" in dired-switches-alist.  This value is not ok, because we're
>>   now in situtation which validation was trying to prevent.  IMO we
>>   should have state for (6), and dired--toggle-b-switch should adjust it
>>   by adding -b to dired-subdir-switches (5).  We should also store
>>   dired-subdir-switches (5) as it is, as currently, because we need to
>>   tell whether -b was present in initial user choice, to be able to
>>   decide whether we need to remove it in "auto" case.
>>
>> Just trying to silence the validation IMO seems wrong.
>>
>> Not having the "full" state (current plus (2) and (6)) also makes for
>> more moot points, like the extract from dired-internal-noselect I posted
>> above.
>>
>> If no one currently can provide the full patch (if my logic is right, of
>> course), then perhaps we better leave this unfixed for now.  You've
>> fixed my original complaint in this bug, this is already an improvement.
>
> I probably need to see an implementation to really understand what
> you're proposing.  But in the mean time, I think it would be better to
> install the last patch I posted (with the change you don't like) than to
> leave the `C-u i' case unhandled, because it's a serious problem (having
> the subdir not appear at all), and the patch prevents that problem, even
> if a better solution is possible.  We could certainly add a FIXME to the
> code referring to this bug report, which can be left open.

I still think I'm opposed to the fix, because 1) it surely will
introduce more subtle bugs (I think I can come up with the cases
easily), 2) it will be harder to clean up later.  A FIXME is IMO better
for now, given that we don't have bug reports on this other than mine.

I'll try to come up with an implementation of what I proposed, but
later.