bug#47850: 28.0.50; find-file-noselect non-nil nowarn argument effect in read-only buffers

[Lars Ingebrigtsen]

dalanicolai@gmail.com writes:

> Find-file-noselect buffer in non-existing directory with non-nil nowarn
> argument e.g:
>
> (switch-to-buffer (find-file-noselect "non-existing-dir/test.el" t))
>
> the buffer will open in read-only mode.
>
> Note that with a nowarn is nil argument, the buffer opens in an
> editable mode as expected.
>
> If it is not considered a technical bug then I would consider it a
> documentation bug.

I think it's a bug.  It stems from this thing:

(defun after-find-file (&optional error warn noauto
                                  _after-find-file-from-revert-buffer
                                  nomodes)
[...]
            (cond
             ((not warn) nil)
             ((and error (file-exists-p buffer-file-name))
              (setq buffer-read-only t)
              "File exists, but cannot be read")
             ((and error (file-symlink-p buffer-file-name))
              "Symbolic link that points to nonexistent file")
             ((not buffer-read-only)
              (if (and warn

Already here the code is pretty dubious, because we've already skipped
all this if warn is non-nil...  Anyway, here's the problem:

[...]

             (t
              (setq buffer-read-only nil)
              (unless (file-directory-p default-directory)
                "Use M-x make-directory RET RET to create the directory and its 
parents")))))

We should do this action even if warn is non-nil, I think?  Or more
generally, we should do all the actions in that cond, but not actually
issue the warning.

I've now done this on the trunk...  this means that those file-exists-p
things are run in the nil WARN case, so the behaviour is slightly
different than before, and it's possible that this may lead to
regressions, I think, but it seems unlikely to me.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no