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bug#61726: [PATCH] Eglot: Support positionEncoding capability
From: |
Eli Zaretskii |
Subject: |
bug#61726: [PATCH] Eglot: Support positionEncoding capability |
Date: |
Thu, 23 Feb 2023 12:39:09 +0200 |
> Cc: João Távora <joaotavora@gmail.com>
> From: Augusto Stoffel <arstoffel@gmail.com>
> Date: Thu, 23 Feb 2023 09:05:35 +0100
>
> There is a new LSP capability allowing the server and client to agree on
> a way to count character offsets. What do you think fo the attached
> patch?
>
> It expresses Eglot's preferences as counting character offsets, then
> byte offsets, then the UTF-16 nonsense, in that order.
>
> I would also suggest preparing the stage to eventually make
> `eglot-current-column-function' and `eglot-move-to-column-function'
> obsolete. For that, I suggest renaming
>
> - eglot-current-column -> eglot--current-column-utf-32
> - eglot-lsp-abiding-column -> eglot--current-columns-utf-16
> - eglot-move-to-column -> eglot--move-to-columns-utf-32
> - eglot-move-to-lsp-abiding-column -> eglot--move-to-columns-utf-16
>
> and then making the old names obsolete aliases of the new names.
Please tell more about this, as I don't think I have a clear enough
idea of the issues and the implications for Emacs.
> +(defun eglot--current-column-utf-8 ()
> + "Calculate current column, counting bytes."
> + (- (position-bytes (point)) (position-bytes (line-beginning-position))))
This is subtly incorrect: position-bytes doesn't cound UTF-8 bytes, it
counts the bytes in the internal representation Emacs uses for buffer
and string text. The differences are minor and subtle, but not
negligible.
> (defun eglot-move-to-column (column)
> - "Move to COLUMN without closely following the LSP spec."
> + "Move to COLUMN, counting Unicode codepoints."
> ;; We cannot use `move-to-column' here, because it moves to *visual*
> ;; columns, which can be different from LSP columns in case of
> ;; `whitespace-mode', `prettify-symbols-mode', etc. (github#296,
> @@ -1490,8 +1505,14 @@ eglot-move-to-column
> (goto-char (min (+ (line-beginning-position) column)
> (line-end-position))))
>
> +(defun eglot--move-to-column-utf-8 (column)
> + "Move to COLUMN, regarded as a byte offset."
> + (goto-char (min (byte-to-position
> + (+ (position-bytes (line-beginning-position)) column))
> + (line-end-position))))
> +
> (defun eglot-move-to-lsp-abiding-column (column)
> - "Move to COLUMN abiding by the LSP spec."
> + "Move to COLUMN, counting UTF-16 code units as in the original LSP spec."
> (save-restriction
> (cl-loop
> with lbp = (line-beginning-position)
> @@ -1515,14 +1536,20 @@ eglot--lsp-position-to-point
> (forward-line (min most-positive-fixnum
> (plist-get pos-plist :line)))
> (unless (eobp) ;; if line was excessive leave point at eob
> - (let ((tab-width 1)
> + (let ((movefn (or eglot-move-to-column-function
> + (pcase (plist-get (eglot--capabilities
> (eglot-current-server))
> + :positionEncoding)
> + ("utf-32" #'eglot-move-to-column)
> + ("utf-8" #'eglot--move-to-column-utf-8)
> + (_ #'eglot-move-to-lsp-abiding-column))))
> + (tab-width 1)
> (col (plist-get pos-plist :character)))
> (unless (wholenump col)
> (eglot--warn
> "Caution: LSP server sent invalid character position %s. Using
> 0 instead."
> col)
> (setq col 0))
> - (funcall eglot-move-to-column-function col)))
> + (funcall movefn col)))
> (if marker (copy-marker (point-marker)) (point)))))
What does this stuff do with double-width or zero-width characters?
Emacs takes character-width into consideration when it counts columns,
but it is unclear to me what do LSP servers do in those cases.
Likewise with characters that are composed on display.
So I think this mess needs to be carefully and elaborately discussed
before we decide how to implement it correctly.
Thanks.
- bug#61726: [PATCH] Eglot: Support positionEncoding capability, Augusto Stoffel, 2023/02/23
- bug#61726: [PATCH] Eglot: Support positionEncoding capability,
Eli Zaretskii <=
- bug#61726: [PATCH] Eglot: Support positionEncoding capability, Augusto Stoffel, 2023/02/23
- bug#61726: [PATCH] Eglot: Support positionEncoding capability, Eli Zaretskii, 2023/02/23
- bug#61726: [PATCH] Eglot: Support positionEncoding capability, Augusto Stoffel, 2023/02/23
- bug#61726: [PATCH] Eglot: Support positionEncoding capability, Eli Zaretskii, 2023/02/23
- bug#61726: [PATCH] Eglot: Support positionEncoding capability, Augusto Stoffel, 2023/02/23
- bug#61726: [PATCH] Eglot: Support positionEncoding capability, Eli Zaretskii, 2023/02/23
- bug#61726: [PATCH] Eglot: Support positionEncoding capability, João Távora, 2023/02/23