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

[Augusto Stoffel]

On Fri, 24 Feb 2023 at 18:01, Eli Zaretskii wrote:

>> From: Augusto Stoffel <arstoffel@gmail.com>
>> Cc: joaotavora@gmail.com,  61726@debbugs.gnu.org
>> Date: Fri, 24 Feb 2023 16:52:27 +0100
>> 
>> >    abcde xyz
>> >
>> > where the \201 byte was replaced by the SPC character.  The latter
>> > string is, of course, perfectly correct UTF-8 sequence, and so doesn't
>> > violate any specs.
>> >
>> > The SPC character as a replacement is, of course, just one example.
>> > We could instead use '?' or U+FFFD REPLACEMENT CHARACTER, or anything
>> > else, and all of those replacements can be encoded in UTF-8 without
>> > any problems.
>> >
>> > Did I make myself clear now?
>> 
>> You made yourself clear the first time.  What I don't understand is, why
>> do you think this is a good idea, because in my view it clearly isn't.
>> 
>> So suppose we lie about the buffer content and say it's "abcde xyz".
>> Then the server sends a diagnostic saying "found unexpected space
>> character at column 6".  What sense does it make to the user?
>
> How can that happen?  Raw bytes can be in comments and in strings, and
> basically nowhere else in a program.  How would the server decide that
> a space is not valid in these contexts?
>
>> Even worse, imagine we then request instructions to reformat the buffer.
>> Suppose that the replacement "abcde xyz" -> "abcde\nxyz" is meaningful
>> in our language but the replacement "abcde\201xyz" -> "abcde\nxyz" is
>> dangerous.  Do we want to get into this kind of trouble?
>
> "Dangerous" in what way?

If someone thinks this is a good and useful feature, of course they
could work on it.  I think the current behavior (json-serialize error)
is better because it sticks to the letter of the specs.

My point of view is very straightforward: you can have language servers;
you can have arbitrary bytes in your files and buffers; but you can't
always have both.  But I'm sure I've already communicated this, sorry
for the repetition.