[eglot] Add support for eglot lsp client in emacs

- Update README
- Add eglot-specifics to cc, rs, py, hs
  removing unused lsp-mode packages when eglot is active
- Add eglot-specific bindings
- Add doctor warnings for debugger +lsp and +peek
- Add eglot-backed lookup-handlers
- Add flycheck checker using eglot for :checkers
  syntax users (using flycheck/flycheck#1676 and
  flycheck/flycheck#1592 discussion).
  This implementation is based on @marsam code, and uses recent
  Flycheck development in order to make the code smaller and
  easier to maintain.

README.md

@@ -73,7 +73,7 @@ Check out [the FAQ][FAQ] for answers to common questions about the project.
 - Optional vim emulation powered by [evil-mode], including ports of popular vim
   plugins like [vim-sneak], [vim-easymotion], [vim-unimpaired] and
   [more][ported-vim-plugins]!
-- Opt-in LSP integration for many languages, using [lsp-mode].
+- Opt-in LSP integration for many languages, using [lsp-mode] or [eglot]
 - Support for *many* programming languages. Includes syntax highlighting,
   linters/checker integration, inline code evaluation, code completion (where
   possible), REPLs, documentation lookups, snippets, and more!
@@ -240,6 +240,7 @@ kind!
 [helm]: https://github.com/emacs-helm/helm
 [ivy]: https://github.com/abo-abo/swiper
 [lsp-mode]: https://github.com/emacs-lsp/lsp-mode
+[eglot]: https://github.com/joaotavora/eglot
 [nix]: https://nixos.org
 [ported-vim-plugins]: modules/editor/evil/README.org#ported-vim-plugins
 [ripgrep]: https://github.com/BurntSushi/ripgrep

modules/config/default/+evil-bindings.el

@@ -345,32 +345,38 @@
 
       ;;; <leader> c --- code
       (:prefix-map ("c" . "code")
-       :desc "Compile"                               "c"   #'compile
-       :desc "Recompile"                             "C"   #'recompile
-       :desc "Jump to definition"                    "d"   #'+lookup/definition
-       :desc "Jump to references"                    "D"   #'+lookup/references
-       :desc "Evaluate buffer/region"                "e"   #'+eval/buffer-or-region
-       :desc "Evaluate & replace region"             "E"   #'+eval:replace-region
-       :desc "Format buffer/region"                  "f"   #'+format/region-or-buffer
-       (:when (featurep! :completion ivy)
-        :desc "Jump to symbol in current workspace" "j"   #'lsp-ivy-workspace-symbol
-        :desc "Jump to symbol in any workspace"     "J"   #'lsp-ivy-global-workspace-symbol)
-       (:when (featurep! :completion helm)
-        :desc "Jump to symbol in current workspace" "j"   #'helm-lsp-workspace-symbol
-        :desc "Jump to symbol in any workspace"     "J"   #'helm-lsp-global-workspace-symbol)
-       :desc "Jump to documentation"                 "k"   #'+lookup/documentation
-       (:when (featurep! :tools lsp)
-        :desc "LSP Execute code action"               "a"   #'lsp-execute-code-action
-        :desc "LSP Organize imports"                  "i"   #'lsp-organize-imports
-        :desc "LSP Rename"                            "r"   #'lsp-rename
-        (:after lsp-mode
-         :desc "LSP"                                   "l"   lsp-command-map))
-       :desc "Send to repl"                          "s"   #'+eval/send-region-to-repl
-       :desc "Delete trailing whitespace"            "w"   #'delete-trailing-whitespace
-       :desc "Delete trailing newlines"              "W"   #'doom/delete-trailing-newlines
-       :desc "List errors"                           "x"   #'flymake-show-diagnostics-buffer
-       (:when (featurep! :checkers syntax)
-        :desc "List errors"                         "x"   #'flycheck-list-errors))
+        (:unless (featurep! :tools lsp +eglot)
+          :desc "LSP Execute code action" "a" #'lsp-execute-code-action
+          :desc "LSP Organize imports" "i" #'lsp-organize-imports
+          (:when (featurep! :completion ivy)
+            :desc "Jump to symbol in current workspace" "j"   #'lsp-ivy-workspace-symbol
+            :desc "Jump to symbol in any workspace"     "J"   #'lsp-ivy-global-workspace-symbol)
+          (:when (featurep! :completion helm)
+            :desc "Jump to symbol in current workspace" "j"   #'helm-lsp-workspace-symbol
+            :desc "Jump to symbol in any workspace"     "J"   #'helm-lsp-global-workspace-symbol)
+          :desc "LSP Rename" "r" #'lsp-rename
+         (:after lsp-mode
+           :desc "LSP"                                   "l"   lsp-command-map))
+        (:when (featurep! :tools lsp +eglot)
+          :desc "LSP Execute code action" "a" #'eglot-code-actions
+          :desc "LSP Format buffer/region" "F" #'eglot-format
+          :desc "LSP Rename" "r" #'eglot-rename
+          :desc "LSP Find declaration" "j" #'eglot-find-declaration
+          :desc "LSP Find implementation" "J" #'eglot-find-implementation)
+        :desc "Compile"                               "c"   #'compile
+        :desc "Recompile"                             "C"   #'recompile
+        :desc "Jump to definition"                    "d"   #'+lookup/definition
+        :desc "Jump to references"                    "D"   #'+lookup/references
+        :desc "Evaluate buffer/region"                "e"   #'+eval/buffer-or-region
+        :desc "Evaluate & replace region"             "E"   #'+eval:replace-region
+        :desc "Format buffer/region"                  "f"   #'+format/region-or-buffer
+        :desc "Jump to documentation"                 "k"   #'+lookup/documentation
+        :desc "Send to repl"                          "s"   #'+eval/send-region-to-repl
+        :desc "Delete trailing whitespace"            "w"   #'delete-trailing-whitespace
+        :desc "Delete trailing newlines"              "W"   #'doom/delete-trailing-newlines
+        :desc "List errors"                           "x"   #'flymake-show-diagnostics-buffer
+        (:when (featurep! :checkers syntax)
+          :desc "List errors"                         "x"   #'flycheck-list-errors))
 
       ;;; <leader> f --- file
       (:prefix-map ("f" . "file")

modules/lang/cc/config.el

@@ -236,9 +236,45 @@ If rtags or rdm aren't available, fail silently instead of throwing a breaking e
       (setq-local company-lsp-cache-candidates nil)
       (lsp!))))
 
+(when (and (featurep! +lsp) (featurep! :tools lsp +eglot))
+  ;; TODO : test this value
+  ;; IS-MAC custom configuration
+  (when IS-MAC
+    (add-to-list 'eglot-workspace-configuration
+                 ((:ccls . ((:clang . ,(list :extraArgs ["-isystem/Library/Developer/CommandLineTools/usr/include/c++/v1"
+                                      "-isystem/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include"
+                                      "-isystem/usr/local/include"]
+                          :resourceDir (string-trim (shell-command-to-string "clang -print-resource-dir")))))))))
+  ;; Eglot specific helper, courtesy of MaskRay
+  (defun eglot-ccls-inheritance-hierarchy (&optional derived)
+  "Show inheritance hierarchy for the thing at point.
+If DERIVED is non-nil (interactively, with prefix argument), show
+the children of class at point."
+  (interactive "P")
+  (if-let* ((res (jsonrpc-request
+                  (eglot--current-server-or-lose)
+                  :$ccls/inheritance
+                  (append (eglot--TextDocumentPositionParams)
+                          `(:derived ,(if derived t :json-false))
+                          '(:levels 100) '(:hierarchy t))))
+            (tree (list (cons 0 res))))
+      (with-help-window "*ccls inheritance*"
+        (with-current-buffer standard-output
+          (while tree
+            (pcase-let ((`(,depth . ,node) (pop tree)))
+              (cl-destructuring-bind (&key uri range) (plist-get node :location)
+                (insert (make-string depth ?\ ) (plist-get node :name) "\n")
+                (make-text-button (+ (point-at-bol 0) depth) (point-at-eol 0)
+                                  'action (lambda (_arg)
+                                            (interactive)
+                                            (find-file (eglot--uri-to-path uri))
+                                            (goto-char (car (eglot--range-region range)))))
+                (cl-loop for child across (plist-get node :children)
+                         do (push (cons (1+ depth) child) tree)))))))
+    (eglot--error "Hierarchy unavailable"))))
 
 (use-package! ccls
-  :when (featurep! +lsp)
+  :when (and (featurep! +lsp) (not (featurep! :tools lsp +eglot)))
   :after lsp
   :init
   (after! projectile

modules/lang/cc/packages.el

@@ -17,7 +17,9 @@
       :pin "404cd0694a")))
 
 (if (featurep! +lsp)
-    (package! ccls :pin "17ec7bb4cf")
+    (unless (featurep! :tools lsp +eglot)
+      ;; ccls package is necessary only for lsp-mode.
+      (package! ccls :pin "17ec7bb4cf"))
   (when (package! irony :pin "5f75fc0c92")
     (package! irony-eldoc :pin "0df5831eaa")
     (when (featurep! :checkers syntax)

modules/lang/haskell/packages.el

@@ -6,6 +6,6 @@
 (when (featurep! +dante)
   (package! dante :pin "4955bc7363")
   (package! attrap :pin "4cf3e4a162"))
-(when (or (featurep! +lsp)
+(when (or (and (featurep! +lsp) (not (featurep! :tools lsp +eglot)))
           (featurep! +ghcide))
   (package! lsp-haskell :pin "582fa27c88"))

modules/lang/python/config.el

@@ -22,7 +22,10 @@ called.")
         python-indent-guess-indent-offset-verbose nil)
 
   (when (featurep! +lsp)
-    (add-hook 'python-mode-local-vars-hook #'lsp!))
+    (add-hook 'python-mode-local-vars-hook #'lsp!)
+    ;; Use "mspyls" in eglot if in PATH
+    (when (executable-find "Microsoft.Python.LanguageServer")
+      (set-eglot-client! 'python-mode '("Microsoft.Python.LanguageServer"))))
   :config
   (set-repl-handler! 'python-mode #'+python/open-repl :persist t)
   (set-docsets! 'python-mode "Python 3" "NumPy" "SciPy")
@@ -98,6 +101,7 @@ called.")
       "Enable `anaconda-mode' if `lsp-mode' is absent and
 `python-shell-interpreter' is present."
       (unless (or (bound-and-true-p lsp-mode)
+                  (bound-and-true-p eglot--managed-mode)
                   (bound-and-true-p lsp--buffer-deferred)
                   (not (executable-find python-shell-interpreter)))
         (anaconda-mode +1))))
@@ -286,7 +290,7 @@ called.")
 
 
 (use-package! lsp-python-ms
-  :when (featurep! +lsp)
+  :when (and (featurep! +lsp) (not (featurep! :tools lsp +eglot)))
   :after lsp-clients
   :preface
   (after! python

modules/lang/python/packages.el

@@ -9,7 +9,7 @@
     (package! flycheck-cython :pin "ecc4454d35")))
 
 ;; LSP
-(when (featurep! +lsp)
+(when (and (featurep! +lsp) (not (featurep! :tools lsp +eglot)))
   (package! lsp-python-ms :pin "5d0c799099"))
 
 ;; Programming environment

modules/lang/rust/config.el

@@ -27,6 +27,11 @@
     (after! rustic-flycheck
       (add-to-list 'flycheck-checkers 'rustic-clippy)))
 
+  (when (featurep! +lsp)
+    (if (featurep! :tools lsp +eglot)
+        (setq rustic-lsp-client 'eglot)
+      (setq rustic-lsp-client 'lsp-mode)))
+
   (map! :map rustic-mode-map
         :localleader
         (:prefix ("b" . "build")

modules/tools/debugger/config.el

@@ -89,7 +89,7 @@
 
 
 (use-package! dap-mode
-  :when (featurep! +lsp)
+  :when (and (featurep! +lsp) (not (featurep! :tools lsp +eglot)))
   :hook (dap-mode . dap-tooltip-mode)
   :after lsp-mode
   :demand t

modules/tools/debugger/doctor.el

@@ -0,0 +1,4 @@
+;;; tools/debugger/doctor.el -*- lexical-binding: t; -*-
+
+(when (and (featurep! +lsp) (featurep! :tools lsp +eglot))
+  (warn! "+lsp flag is not compatible with :tools (lsp +eglot). Choose only one of (eglot or dap-mode) please"))

modules/tools/lsp/README.org

@@ -56,10 +56,16 @@ As of this writing, this is the state of LSP support in Doom Emacs:
 ** Module Flags
 + =+peek= Use =lsp-ui-peek= when looking up definitions and references with
   functionality from the =:tools lookup= module.
++ =+eglot= Use [[https://elpa.gnu.org/packages/eglot.html][Eglot]] instead of [[https://github.com/emacs-lsp/lsp-mode][LSP-mode]] to implement the LSP client in
+  Emacs.
 
 ** Plugins
 + [[https://github.com/emacs-lsp/lsp-mode][lsp-mode]]
 + [[https://github.com/emacs-lsp/lsp-ui][lsp-ui]]
++ [[https://github.com/emacs-lsp/lsp-ivy][lsp-ivy]]
++ [[https://github.com/emacs-lsp/helm-lsp][helm-lsp]]
++ [[https://github.com/joaotavora/eglot][eglot]]
+
 ** Hacks
 + ~lsp-mode~ has been modified not to automatically install missing LSP servers.
   This is done to adhere to our "Your system, your rules" mantra, which insist
@@ -75,15 +81,37 @@ You'll find a table that lists available language servers and how to install
 them [[https://github.com/emacs-lsp/lsp-mode#supported-languages][in the lsp-mode project README]]. The documentation of the module for your
 targeted language will contain brief instructions as well.
 
+For eglot users, you can see the list of [[https://github.com/joaotavora/eglot/blob/master/README.md#connecting-to-a-server][default servers supported in the README]].
+There is also instructions to add another server easily.
+
 * TODO Features
 ** LSP-powered project search
-When =:completion ivy= or =:completion helm= is active, LSP is used to search a
-symbol indexed by the LSP server :
+Without the =+eglot= flag, and when =:completion ivy= or =:completion helm= is
+active, LSP is used to search a symbol indexed by the LSP server :
 | Keybind   | Description                         |
 |-----------+-------------------------------------|
 | =SPC c j= | Jump to symbol in current workspace |
 | =SPC c J= | Jump to symbol in any workspace     |
+** Differences between eglot and lsp-mode
+Entering the debate about which one to use would be useless. Doom provides an
+easy way to switch out lsp client implementations so you can test for yourself
+which one you prefer.
+
+Mainly, from a code point of view, lsp-mode has a lot of custom code for UI
+(=lsp-ui-peek=, =lsp-ui-sideline=, ...), while eglot is more barebones with a
+closer integration with "more basic" emacs packages (=eldoc=, =xref=, ...).
 
 * TODO Configuration
 
 * TODO Troubleshooting
+** My language server is not found
+Check the entry in the [[../../../docs/faq.org][FAQ]] about "Doom can't find my executables/doesn't inherit
+the correct ~PATH~"
+** LSP/Eglot is not started automatically in my buffer
+Make sure that you added the =+lsp= flag to the language you're using too in
+your init.el :
+#+BEGIN_SRC diff
+:lang
+-python
++(python +lsp)
+#+END_SRC

modules/tools/lsp/autoload/common.el

@@ -0,0 +1,9 @@
+;;; tools/lsp/autoload/common.el -*- lexical-binding: t; -*-
+
+;;;###autodef
+(defun lsp! ()
+  "Dispatch to call the currently used lsp client entrypoint"
+  (interactive)
+  (if (featurep! +eglot)
+      (eglot-ensure)
+    (lsp-deferred)))

modules/tools/lsp/autoload/eglot.el

@@ -0,0 +1,19 @@
+;;; tools/lsp/autoload/eglot.el -*- lexical-binding: t; -*-
+;;;###if (featurep! +eglot)
+
+;;;###autodef
+(defun set-eglot-client! (mode server-call)
+  "Add SERVER-CALL list as a possible lsp server for given major MODE.
+
+Example : (set-eglot-client! 'python-mode `(,(concat doom-etc-dir \"lsp/mspyls/Microsoft.Python.LanguageServer\")))"
+  (when (featurep! +eglot)
+    (add-to-list 'eglot-server-programs `(,mode . ,server-call))))
+
+;;;###autoload
+(defun +eglot/documentation-lookup-handler ()
+  "Documentation lookup handler using eglot :document/hover handler.
+
+Mostly a rewrite of `eglot-help-at-point', which should be used interactively."
+  (interactive)
+  (eglot-help-at-point)
+  (display-buffer eglot--help-buffer))

modules/tools/lsp/autoload.el → modules/tools/lsp/autoload/lsp-mode.el

@@ -1,4 +1,5 @@
-;;; feature/lsp/autoload.el -*- lexical-binding: t; -*-
+;;; tools/lsp/autoload/lsp-mode.el -*- lexical-binding: t; -*-
+;;;###if (not (featurep! +eglot))
 
 ;;;###autodef
 (defun set-lsp-priority! (client priority)
@@ -9,9 +10,6 @@
             priority)
     (error "No LSP client named %S" client)))
 
-;;;###autodef
-(defalias 'lsp! #'lsp-deferred)
-
 ;;;###autoload
 (defun +lsp/uninstall-server (dir)
   "Delete a LSP server from `lsp-server-install-dir'."

modules/tools/lsp/config.el

@@ -7,15 +7,38 @@ workspace buffer is closed.
 This delay prevents premature server shutdown when a user still intends on
 working on that project after closing the last buffer.")
 
+;; TODO : set eglot-events-buffer-size to nil in doom-debug-mode
 
 ;;
 ;;; Packages
 
+(use-package! eglot
+  :when (featurep! +eglot)
+  :init
+  (setq eglot-sync-connect 1
+        eglot-connect-timeout 10
+        eglot-autoshutdown t
+        eglot-send-changes-idle-time 0.5
+        ;; NOTE: Do NOT set eglot-auto-display-help-buffer to t.
+        ;; With popup-rule! :select t, eglot will steal focus from the source code very often.
+        eglot-auto-display-help-buffer nil)
+  :config
+  (set-popup-rule! "^\\*eglot-help" :size 0.35 :quit t :select t)
+  (when (featurep! :checkers syntax)
+    ;; Eager loading which is okay-ish since we want eglot to feed flycheck as soon as possible.
+    (load! "flycheck-eglot.el")
+    (require 'flycheck-eglot))
+  (set-lookup-handlers! 'eglot--managed-mode
+    :documentation #'+eglot/documentation-lookup-handler
+    :definition '(xref-find-definitions :async t)
+    :references '(xref-find-references :async t)))
+
 (use-package! lsp-mode
+  :unless (featurep! +eglot)
   :commands lsp-install-server
   :init
   (setq lsp-session-file (concat doom-etc-dir "lsp-session"))
-  ;; Don't prompt the user for the project root every time we open a new
+  ;; Do not prompt the user for the project root every time we open a new
   ;; lsp-worthy file, instead, try to guess it with projectile.
   (setq lsp-auto-guess-root t)
   ;; Auto-kill LSP server after last workspace buffer is killed.
@@ -126,7 +149,7 @@ This also logs the resolved project root, if found, so we know where we are."
     (defun +lsp-init-flycheck-or-flymake-h ()
       "Set up flycheck-mode or flymake-mode, depending on `lsp-diagnostic-package'."
       (pcase lsp-diagnostic-package
-        ((or :auto 'nil) ; try flycheck, fall back to flymake
+        ((or :auto 'nil)                ; try flycheck, fall back to flymake
          (let ((lsp-diagnostic-package
                 (if (require 'flycheck nil t) :flycheck :flymake)))
            (+lsp-init-flycheck-or-flymake-h)))
@@ -179,6 +202,7 @@ auto-killed (which is a potentially expensive process)."
 
 
 (use-package! lsp-ui
+  :unless (featurep! +eglot)
   :hook (lsp-mode . lsp-ui-mode)
   :config
   (setq lsp-ui-doc-max-height 8
@@ -200,10 +224,12 @@ auto-killed (which is a potentially expensive process)."
 
 
 (use-package! helm-lsp
+  :unless (featurep! +eglot)
   :when (featurep! :completion helm)
   :commands helm-lsp-workspace-symbol helm-lsp-global-workspace-symbol)
 
 
 (use-package! lsp-ivy
+  :unless (featurep! +eglot)
   :when (featurep! :completion ivy)
   :commands lsp-ivy-workspace-symbol lsp-ivy-global-workspace-symbol)

modules/tools/lsp/doctor.el

@@ -0,0 +1,3 @@
+;;; tools/lsp/doctor.el -*- lexical-binding: t; -*-
+
+(assert! (not (and (featurep! +eglot) (featurep! +peek))) "+eglot and +peek flags are not compatible. Peek uses lsp-mode, while Eglot is another package altogether for LSP.")