Xref/tags/lsp possible bug

[Alessandro Bertulli <alessandro.bertulli96@gmail.com>]

Hi all!

I just stumbled upon a very strange behavior of Emacs, I don't know if
it is a bug or an error of my configuration. Basically, I noticed two
things:

- First, when using LSP modes (both lsp-mode and eglot), the command
  xref-find-definitions only acts on the symbol under point. I
  explain: usually, in vanilla Emacs (emacs -q) if point is on a
  whitespace/not on a symbol, invoking the command (bound to M-.) will
  prompt you for an identifier to search for. However, when LSP is
  active, it directly searches for an empty symbol, for example
  reporting something similar to: "Symbol  not found" (not the double
  space, which makes me think it searches for a symbol named ""). As I
  said, this happend both for lsp-mode and eglot, so maybe is a
problem of xref?

- Second, and minor: while I was investigating, I noticed that,
  depending on the loaded packages, when giving M-., xref sometimes
  asks for the symbol to search, sometimes it asks the TAGS table
first. What package can be the problem?

Do you think it is a bug of Emacs? Do you know a way to resolve?
Thanks to all!

############
I report some useful infos:

Emacs version: This is GNU Emacs 28.1 (build 1, x86_64-pc-linux-gnu, GTK+
Version 3.24.33, cairo version 1.17.6) of 2022-04-20
lsp-mode version: 20220422.2059
xref version: 1.4.1

##########
Steps to reproduce:
-First bug:
 - launch emacs -q
 - go on an C++ file
 - on a whitespace, give M-.. The prompt says "Find definition of: "
 - close and restart with the provided file (emacs -q --load file,
  see end of the mail)
 - go on the same C++ file
 - launch lsp-mode (M-x lsp)
 - on the same whitespace, give M-. The minibuffer says "Unable to
 find symbol  in current document" (note the bouble space). In
 *Messages* buffer, the error is reported perfized with the string
 "user-error: ".
 - give M-x lsp-find-definition on the same whitespace. The minibuffer
 says: "LSP :: Not found for: " (note the space at the end).


-Second bug:
 - launch emacs -q
 - go on a C++ file
 - on a whitespace, give M-. The prompt says "Find definitions of: "
 - close and restart with provided file (emacs -q --load file)
 - go on the same C++ file
 - on the same whitespace, give M-. The prompt says "Visit tags table
   (default TAGS): "
 - go on an elisp file, do the same, the prompt says "Find definitions of: "

#############
Test init file

(custom-set-variables
 ;; custom-set-variables was added by Custom.
 ;; If you edit it by hand, you could mess it up, so be careful.
 ;; Your init file should contain only one such instance.
 ;; If there is more than one, they won't work right.
 '(package-selected-packages
   '(helpful transient-dwim ivy projectile eglot magit lsp-ui flycheck
which-key yasnippet-snippets yasnippet lsp-mode company))
 )

;;--------------
;; Enable MELPA
;;-------------

(require 'package)
(add-to-list 'package-archives '("melpa" . "https://melpa.org/packages/") t)
;; Comment/uncomment this line to enable MELPA Stable if desired.  See
`package-archive-priorities`
;; and `package-pinned-packages`. Most users will not need or want to do
this.
;;(add-to-list 'package-archives '("melpa-stable" . "
https://stable.melpa.org/packages/") t)
(package-initialize)


(setq pkg-list '(helpful transient-dwim ivy projectile eglot magit lsp-ui
flycheck which-key yasnippet-snippets yasnippet lsp-mode company))
(mapc (lambda (pkg)
          (unless (package-installed-p pkg)
            (package-install pkg))
          (require pkg))
      pkg-list)

;;------------
;; Various
;;-------------
(setq confirm-kill-emacs #'y-or-n-p)
(tool-bar-mode 0)
(global-flycheck-mode)

(setq sentence-end-double-space nil)
(show-paren-mode)

;;--------------
;; Help - transient-dwim
;;--------------
(which-key-mode 1)
(global-set-key (kbd "C-M-SPC") #'which-key-show-major-mode)
(global-set-key (kbd "M-=") 'transient-dwim-dispatch)

;; Helpful ---------------
(global-set-key (kbd "C-h f") #'helpful-callable)
(global-set-key (kbd "C-h v") #'helpful-variable)
(global-set-key (kbd "C-h k") #'helpful-key)
(global-set-key (kbd "C-h M-.") #'helpful-at-point)


;;------------
;; Ivy
;;----------
(ivy-mode 1)
(setq ivy-use-virtual-buffers t)
(setq ivy-count-format "(%d/%d) ")

;;-----------------
;; YASnippet
;;-----------------
(require 'yasnippet)
(yas-reload-all)
(yas-global-mode)

;;--------------
;;Projectile
;;-------------------
(require 'projectile)
(define-key projectile-mode-map (kbd "C-c p") 'projectile-command-map)
(projectile-mode +1)

;;------------------
;; Eglot
;;------------------
(require 'eglot)
;;use flychech instead of flymake
(add-to-list 'eglot-stay-out-of 'flymake)

;;suggested by the repo
(define-key eglot-mode-map (kbd "C-c r") 'eglot-rename)
(define-key eglot-mode-map (kbd "C-c o")
'eglot-code-action-organize-imports)
(define-key eglot-mode-map (kbd "C-c h") 'eldoc)

;;----------------
;; Language Server Protocol
;;--------------
(require 'lsp-mode)
;; apparently, this must be done before loading in any way lsp-mode
(setq lsp-keymap-prefix "C-c l")
(define-key lsp-mode-map (kbd "C-c l") lsp-command-map)
;; this must be called after to let which-key see the new prefix, think
(add-hook 'lsp-mode-hook 'lsp-enable-which-key-integration)
(define-key lsp-mode-map (kbd "M-RET") 'lsp-execute-code-action)
;;suggested by lsp-java doc
(setq lsp-completion-enable-additional-text-edit nil)

;;copied from https://emacs-lsp.github.io/lsp-mode/tutorials/CPP-guide/
;;probably is better
(with-eval-after-load 'lsp-mode
  (add-hook 'lsp-mode-hook #'lsp-enable-which-key-integration)
  (yas-global-mode))

;; lsp-mode is not activated by default in the c++-hook so that
;; the second bug can also be reproduced.
;; However, if needed, uncomment this line
;; (add-hook 'c++-mode-hook 'lsp)

;;---------------
;; lsp-ui
;;--------------
(eval-after-load 'lsp
  (eval-after-load 'lsp-ui
    (setq lsp-ui-sideline-show-hover t)
    ))

;;-------------------
;; Company (should be called after lsp-mode?)
;;------------------
(add-hook 'prog-mode-hook 'company-mode)
(define-key prog-mode-map (kbd "C-M-i") 'company-complete)
(eval-after-load 'comapny '(define-key company-mode-map (kbd "<C-tab>")
'company-complete))
(eval-after-load 'company '(define-key company-active-map (kbd "<tab>")
'company-complete))
(eval-after-load 'company '(add-to-list 'company-backends 'company-capf))
(setq company-minimum-prefix-length 1)

(run-hooks 'after-init-hook)