bug#28691: [PATCH] Add file name handler support for 'make-process' (Bug#28691)

[Eli Zaretskii <eliz@gnu.org>]

> From: Philipp Stephani <p.stephani2@gmail.com>
> Date: Mon, 17 Dec 2018 00:39:36 +0100
> Cc: Philipp Stephani <phst@google.com>
> 
> --- a/etc/NEWS
> +++ b/etc/NEWS
> @@ -1407,6 +1407,10 @@ un-obsoleting it.
>  +++
>  ** New function 'group-name' returns a group name corresponding to GID.
>  
> +** 'make-process' now takes a keyword argument ':file-handler'; if
> +that is non-nil, it will search for a file name handler for
> +'default-directory'.

I think the feature you introducing is not to "search for a file name
handler for 'default-directory'", the feature is to (attempt to) make
a remote process using that file handler.  I think the documentation
should make that more explicit, because I very much doubt it could be
otherwise gleaned from this description.

I'd also suggest to say "... the current buffer's
'default-directory'", just to make sure people don't miss that.

> +:file-handler FILE-HANDLER -- If FILE-HANDLER is non-nil, then search
> +for a file name handler for `default-directory'.

Likewise here.  Also, please describe what happens if the search for
the handler fails.

> +(ert-deftest make-process/file-handler ()
> +  "Check that the ‘:file-handler’ argument of ‘make-process’
> +works as expected."
> +  (let ((file-handler-calls 0))
> +    (cl-flet ((file-handler
> +               (&rest args)
> +               (should (equal default-directory "test-handler:/dir/"))
> +               (should (equal args '(make-process :name "name"
> +                                                  :command ("/bin/true")

/bin/true is not portable enough, I suggest to use Emacs itself
instead.

> +      (let ((file-name-handler-alist
> +             (cons (cons (rx bos "test-handler:") #'file-handler)
> +                   file-name-handler-alist))

I think it would be preferable to empty file-name-handler-alist of any
other members -- that will make this test 100% deterministic.

Thanks.