bug#25653: 25.1.91; buffer-file-name reports non-existing file

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tags 25653 notabug
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Andreas Röhler <andreas.roehler@easy-emacs.de> writes:

> Emacs -Q
>
> Open some non-existing foo.py
>
> Before saving
>
> M-x buffer-file-name RET reports PATH-to/foo.py as buffer-file-name.
>
> IMO buffer-file-name only should get a value different from nil, if
> the buffer is connected with an existing file, as docu says:

> Return name of file BUFFER is visiting, or nil if none.

I disagree this is a bug, in `(emacs) Visiting' we see

   Successful visiting of any file, whether existing or not,

i.e., we can successfully visit a non-existing file.  Furthermore, the
existence of a file can change asynchronously, so it's not really
sensible to expect an Emacs variable to reflect that.  The state of
"visiting" just means that Emacs will write the buffer contents out to
the visited file when saved.