bug#59338: 29.0.50; Commit 1a2d603bb3 breaks Eglot on Windows

[Danny Freeman]

Augusto Stoffel <arstoffel@gmail.com> writes:

> On Thu, 17 Nov 2022 at 19:06, Eli Zaretskii wrote:
>
>> Both are wrong, right?  The correct URL should AFAIU be
>>
>>   file:///d:/digestif-test/tikz-test.tex
>>
>> IOW, the problem is that the URL is being run through url-encode-url,
>> which doesn't support file:// URLs on Windows properly.
>
> While we are at it, note that
>
>   (url-filename
>     (url-generic-parse-url "file:///d:/digestif-test/tikz-test.tex"))
>   => "/d:/digestif-test/tikz-test.tex"
>
> is not the right file name under Windows.  Eglot treats this special
> case correctly, but every package that deals with file URLs has to
> repeat the work.  So there should be a helper function in Emacs for
> this.

With the original problem: we're now getting a false positive in
eglot when checking for URLs being passed to `eglot--path-to-uri` when
the path is a windows path.

Is there something we can do to detect a windows path and continue
treating it as a path like we were before this change?

```
(defun eglot--path-to-uri (path)
  "URIfy PATH."
  (let ((truepath (file-truename path)))
    (if (and (url-type (url-generic-parse-url truepath))
             (NOT_WINDOWS_PATH truepath) ;; what would this be?
             )
      ;; ... blah blah blah
```

If there is no function available already, it may be enough to check if
the return value of `url-type` is not 1 character. Looking at this list
of what I believe are official URI schemes, all of them have at least
two characters: 
https://www.iana.org/assignments/uri-schemes/uri-schemes.xhtml 

-- 
Danny Freeman