bug#61726: [PATCH] Eglot: Support positionEncoding capability

[Augusto Stoffel]

On Fri, 24 Feb 2023 at 13:45, João Távora wrote:

> I don't see how this is relevant to the code-point counting problem here,
> though.

The relevance is in how the offset-counting function should proceed when
the buffer is not UTF-8 encodable:

- My patch has a garbage-in garbage-out behavior.

- Eli made a suggestion he deems more correct, but is more expensive.
  Since JSON must be UTF-8 encoded for data exchange purposes, I don't
  see the benefit, and in fact I consider this option just a different
  choice of garbage-in garbage-out behavior.

- A third option is to make the function throw an error.  However, if
  the buffer is not UTF-8 encodable, we already get an error from
  json-serialize, because it doesn't let you generate invalid JSON:

    (progn
     (insert ?" (max-char) ?")
     (json-serialize (buffer-substring-no-properties (pos-bol)
     (pos-eol))))

     ⇒ Debugger entered--Lisp error: (wrong-type-argument utf-8-string-p "     
\"\377\"")