bug#32274: (interactive "F") silently expands a directory to the current buffer's path

bug#32274: (interactive "F") silently expands a directory to the current buffer's path

[Andrea Cardaci]

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The value returned by (interactive "F") is not the one provided by the user.

1. Create a file, say /tmp/foo.el:

(defun foo (path)
  (interactive "F")
  (message path))

2. M-x evaluate-buffer

3. M-x foo and chose /tmp/.

The value presented in the echo area is /tmp/foo.el, this is undesirable
and very dangerous IMHO. It happens with both Emacs 24 and 26.

Is this a bug or I'm overlooking something?


Andrea

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bug#32274: (interactive "F") silently expands a directory to the current buffer's path

[Noam Postavsky]

Andrea Cardaci <cyrus.and@gmail.com> writes:

> The value returned by (interactive "F") is not the one provided by the user.
>
> 1. Create a file, say /tmp/foo.el:
>
> (defun foo (path)
>   (interactive "F")
>   (message path))
>
> 2. M-x evaluate-buffer
>
> 3. M-x foo and chose /tmp/.
>
> The value presented in the echo area is /tmp/foo.el, this is undesirable and very dangerous IMHO. It happens with both Emacs 24 and 26.
>
> Is this a bug or I'm overlooking something?

"F" calls read-file-name, passing nil for all args:

    DEFAULT-FILENAME specifies the default file name to return if the
    user exits the minibuffer with the same non-empty string inserted
    by this function [...]  If DEFAULT-FILENAME is omitted or
    nil [...] if the current buffer is visiting a file,
    that file serves as the default [...]

So it seems to be on purpose.

bug#32274: (interactive "F") silently expands a directory to the current buffer's path

[Andrea Cardaci]

> So it seems to be on purpose.

OK, that makes sense, thank you.

I still don't think it's a wise choice though, besides being prone to
mistakes it also makes it impossible to choose /tmp/ in the above
example, while other directories can be happily selected.

bug#32274: (interactive "F") silently expands a directory to the current buffer's path

[Noam Postavsky]

Andrea Cardaci <cyrus.and@gmail.com> writes:

> I still don't think it's a wise choice though, besides being prone to
> mistakes it also makes it impossible to choose /tmp/ in the above
> example, while other directories can be happily selected.

You can enter "/tmp" (i.e., delete the trailing slash), but I guess
(interactive "G") is the behaviour you are looking for.

bug#32274: (interactive "F") silently expands a directory to the current buffer's path

[Andrea Cardaci]

> You can enter "/tmp" (i.e., delete the trailing slash), but I guess
> (interactive "G") is the behaviour you are looking for.

Yes sure, I just find odd this behavior. Thanks for your time.