bug#57777: 28.2; `vc-dir' picks incorrect backend.

bug#57777: 28.2; `vc-dir' picks incorrect backend.

[Mike Woolley]

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Steps to repro:

Start with a directory having both .Git and CVS sub-directories.
Emacs -Q
(setq vc-handled-backends '(Git CVS))
(vc-dir)
Observe `vc-dir’ incorrectly uses the CVS backend rather than Git.
Open one of the vc-managed files and the Git backend is (correctly) chosen.
This used to work fine in emacs < 28.
This issue was masked in 28.1 by bug#54935 forcing me to choose the backend manually.

Thanks,
Mike

In GNU Emacs 28.2 (build 1, aarch64-apple-darwin21.1.0, NS appkit-2113.00 Version 12.0.1 (Build 21A559))
 of 2022-09-12 built on armbob.lan
Windowing system distributor 'Apple', version 10.3.2113
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bug#57777: 28.2; `vc-dir' picks incorrect backend.

[Lars Ingebrigtsen]

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Mike Woolley <mike@bulsara.com> writes:

> 1 Start with a directory having both .Git and CVS sub-directories.
> 2 Emacs -Q
> 3 (setq vc-handled-backends '(Git CVS))
> 4 (vc-dir)
> 5 Observe `vc-dir’ incorrectly uses the CVS backend rather than Git.

I'm unable to reproduce this problem with Emacs 28.2 (or the current
trunk).

I did:

mkdir /tmp/vc /tmp/vc/.git /tmp/vc/CVS
emacs -Q

and then:

(setq vc-handled-backends '(Git CVS))
(vc-dir "/tmp/vc")

And got:


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Are there any steps missing in your recipe that's needed to reproduce
the problem?

bug#57777: 28.2; `vc-dir' picks incorrect backend.

[Lars Ingebrigtsen]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> I'm unable to reproduce this problem with Emacs 28.2 (or the current
> trunk).

Sorry; I was testing in the wrong checkout -- I'm now rebuilding the
real emacs-28.2 release and will re-test.

bug#57777: 28.2; `vc-dir' picks incorrect backend.

[Lars Ingebrigtsen]

Lars Ingebrigtsen <larsi@gnus.org> writes:

>> I'm unable to reproduce this problem with Emacs 28.2 (or the current
>> trunk).
>
> Sorry; I was testing in the wrong checkout -- I'm now rebuilding the
> real emacs-28.2 release and will re-test.

I've now redone the tests, but I'm still not able to reproduce the
problem.

bug#57777: 28.2; `vc-dir' picks incorrect backend.

[Mike Woolley]

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Thanks for looking at this Lars.

The steps you tried also work correctly for me, so clearly the problem is a bit more specific than I initially thought!

I stepped through `vc-responsible-backend’ in the debugger when executing `vc-dir’ on one of the directories where I have this problem (my home directory in the following example).
This bit of code:

 (vc-call-backend backend 'responsible-p file)

returns "~/“ for the Git backend, but "/Users/mike/“ for the CVS backend.

Further down, this next bit of code looks for the longest directory string in an attempt to find the deepest subdirectory:

  ;; Several roots; we seem to have one vc inside another's
  ;; directory.  Choose the most specific.
  (caar (sort dirs (lambda (d1 d2)
                     (< (length (cdr d2)) (length (cdr d1))))))))

Which explains why it picks the CVS backend, because "/Users/mike/“ is longer than "~/“ 😊

So in other words, the missing step from my instructions is the directory has to be under the user’s home directory.

I would have thought the fix would be either to make `responsible-p’ return the same string or expand the “~” before executing the length comparison above.

Thanks,
Mike

> On 14 Sep 2022, at 15:43, Lars Ingebrigtsen <larsi@gnus.org> wrote:
> 
> Lars Ingebrigtsen <larsi@gnus.org> writes:
> 
>>> I'm unable to reproduce this problem with Emacs 28.2 (or the current
>>> trunk).
>> 
>> Sorry; I was testing in the wrong checkout -- I'm now rebuilding the
>> real emacs-28.2 release and will re-test.
> 
> I've now redone the tests, but I'm still not able to reproduce the
> problem.


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bug#57777: 28.2; `vc-dir' picks incorrect backend.

[Mike Woolley]

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I should also mention that I tested changing the code to the following and it fixed the problem:

     (when-let ((dir (expand-file-name
			    (vc-call-backend
                               backend 'responsible-p file))))

Thanks,
Mike

> On 15 Sep 2022, at 15:53, Mike Woolley <mike@bulsara.com> wrote:
> 
> Thanks for looking at this Lars.
> 
> The steps you tried also work correctly for me, so clearly the problem is a bit more specific than I initially thought!
> 
> I stepped through `vc-responsible-backend’ in the debugger when executing `vc-dir’ on one of the directories where I have this problem (my home directory in the following example).
> This bit of code:
> 
>  (vc-call-backend backend 'responsible-p file)
> 
> returns "~/“ for the Git backend, but "/Users/mike/“ for the CVS backend.
> 
> Further down, this next bit of code looks for the longest directory string in an attempt to find the deepest subdirectory:
> 
>   ;; Several roots; we seem to have one vc inside another's
>   ;; directory.  Choose the most specific.
>   (caar (sort dirs (lambda (d1 d2)
>                      (< (length (cdr d2)) (length (cdr d1))))))))
> 
> Which explains why it picks the CVS backend, because "/Users/mike/“ is longer than "~/“ 😊
> 
> So in other words, the missing step from my instructions is the directory has to be under the user’s home directory.
> 
> I would have thought the fix would be either to make `responsible-p’ return the same string or expand the “~” before executing the length comparison above.
> 
> Thanks,
> Mike
> 
>> On 14 Sep 2022, at 15:43, Lars Ingebrigtsen <larsi@gnus.org <mailto:larsi@gnus.org>> wrote:
>> 
>> Lars Ingebrigtsen <larsi@gnus.org <mailto:larsi@gnus.org>> writes:
>> 
>>>> I'm unable to reproduce this problem with Emacs 28.2 (or the current
>>>> trunk).
>>> 
>>> Sorry; I was testing in the wrong checkout -- I'm now rebuilding the
>>> real emacs-28.2 release and will re-test.
>> 
>> I've now redone the tests, but I'm still not able to reproduce the
>> problem.
> 


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bug#57777: 28.2; `vc-dir' picks incorrect backend.

[Lars Ingebrigtsen]

Mike Woolley <mike@bulsara.com> writes:

> I should also mention that I tested changing the code to the following and it fixed the
> problem:
>
>      (when-let ((dir (expand-file-name
>    (vc-call-backend
>                                backend 'responsible-p file))))

Thanks; I've now pushed something along these lines to Emacs 29.