Rethink lsp defaults

+ Allow LSP to prompt to install servers. All this machinary just adds
more confusion for beginners, and at least LSP asks for your permission
before it does it.
+ Reverts lsp-enable-file-watchers and lsp-enable-indentation to their
default (enabled), hopefully to help lsp-java, lsp-dart, and lsp-clojure
users, for whom file-watchers seems to be necessary.
+ Apply GC/IPC optimizations globally, to ensure their reach. By only
setting them buffer-locally we don't have a guarantee that subprocesses
will be affected when the lsp buffer isn't focused.

Closes #3989

Co-authored-by: Eric Dallo <ercdll1337@gmail.com>

modules/tools/lsp/+eglot.el

@@ -2,7 +2,7 @@
 
 (use-package! eglot
   :commands eglot eglot-ensure
-  :hook (eglot-managed-mode . +lsp-init-optimizations-h)
+  :hook (eglot-managed-mode . +lsp-optimization-mode)
   :init
   (setq eglot-sync-connect 1
         eglot-connect-timeout 10
@@ -34,11 +34,13 @@ server getting expensively restarted when reverting buffers."
     (letf! (defun eglot-shutdown (server)
              (if (or (null +lsp-defer-shutdown)
                      (eq +lsp-defer-shutdown 0))
-                 (funcall eglot-shutdown server)
+                 (prog1 (funcall eglot-shutdown server)
+                   (+lsp-optimization-mode -1))
                (run-at-time
                 (if (numberp +lsp-defer-shutdown) +lsp-defer-shutdown 3)
                 nil (lambda (server)
                       (unless (eglot--managed-buffers server)
-                        (funcall eglot-shutdown server)))
+                        (prog1 (funcall eglot-shutdown server)
+                          (+lsp-optimization-mode -1))))
                 server)))
       (funcall orig-fn server))))

modules/tools/lsp/+lsp.el

@@ -4,13 +4,6 @@
   "The backends to prepend to `company-backends' in `lsp-mode' buffers.
 Can be a list of backends; accepts any value `company-backends' accepts.")
 
-(defvar +lsp-auto-install-servers nil
-  "If non-nil, automatically install LSP servers.
-
-`lsp-mode' will prompt you to install an LSP server when you enter a major mode
-with LSP support but no available server. I believe changes to your system
-should be a deliberate act (as is flipping this variable).")
-
 
 ;;
 ;;; Packages
@@ -18,30 +11,27 @@ should be a deliberate act (as is flipping this variable).")
 (use-package! lsp-mode
   :commands lsp-install-server
   :init
-  (setq lsp-session-file (concat doom-etc-dir "lsp-session"))
+  ;; Don't touch ~/.emacs.d, which could be purged without warning
-  ;; For `lsp-clients'
+  (setq lsp-session-file (concat doom-etc-dir "lsp-session")
-  (setq lsp-server-install-dir (concat doom-etc-dir "lsp/"))
+        lsp-server-install-dir (concat doom-etc-dir "lsp/"))
   ;; Don't auto-kill LSP server after last workspace buffer is killed, because I
   ;; will do it for you, after `+lsp-defer-shutdown' seconds.
   (setq lsp-keep-workspace-alive nil)
 
-  ;; Let doom bind the lsp keymap.
-  (when (featurep! :config default +bindings)
-    (setq lsp-keymap-prefix nil))
-
   ;; NOTE I tweak LSP's defaults in order to make its more expensive or imposing
   ;;      features opt-in. Some servers implement these poorly and, in most
   ;;      cases, it's safer to rely on Emacs' native mechanisms (eldoc vs
   ;;      lsp-ui-doc, open in popup vs sideline, etc).
 
   ;; Disable features that have great potential to be slow.
-  (setq lsp-enable-file-watchers nil
+  (setq lsp-enable-folding nil
-        lsp-enable-folding nil
         lsp-enable-text-document-color nil)
+  ;; Reduce unexpected modifications to code
+  (setq lsp-enable-on-type-formatting nil)
 
-  ;; Disable features that modify our code without our permission.
+  ;; Let doom bind the lsp keymap.
-  (setq lsp-enable-indentation nil
+  (when (featurep! :config default +bindings)
-        lsp-enable-on-type-formatting nil)
+    (setq lsp-keymap-prefix nil))
 
   :config
   (pushnew! doom-debug-variables 'lsp-log-io 'lsp-print-performance)
@@ -62,43 +52,6 @@ should be a deliberate act (as is flipping this variable).")
     :type-definition #'lsp-find-type-definition
     :references #'lsp-find-references)
 
-  (when lsp-auto-configure
-    (mapc (lambda (package) (require package nil t))
-          (cl-remove-if #'featurep lsp-client-packages)))
-
-  (defadvice! +lsp--dont-auto-install-servers-a (orig-fn &rest args)
-    "Replace auto-install behavior with warning and support indirect buffers."
-    :around #'lsp
-    (if +lsp-auto-install-servers
-        (apply orig-fn args)
-      (letf! ((buffer-file-name
-               ;; Add support for indirect buffers (org src or capture buffers)
-               (or buffer-file-name
-                   (buffer-file-name (buffer-base-buffer))))
-              ;; Already loaded them. No need to do so again.
-              (lsp-client-packages nil)
-              ;; `lsp' is normally eager to automatically install LSP servers, or
-              ;; prompting to do so, but (in my opinion) server installation
-              ;; should be a deliberate act by the end-user:
-              (defun lsp--completing-read (msg clients &rest _)
-                (lsp--warn (concat msg "%s\n"
-                                   "  Use `M-x lsp-install-server' to install a supported server, or read "
-                                   "https://emacs-lsp.github.io/lsp-mode/page/languages for more.")
-                           (mapcar #'lsp--client-server-id clients))
-                (throw 'not-installed nil)))
-        (catch 'not-installed
-          (apply orig-fn args)))))
-
-  (defadvice! +lsp--respect-user-defined-checkers-a (orig-fn &rest args)
-    "Set up flycheck-mode or flymake-mode, depending on `lsp-diagnostic-package'."
-    :around #'lsp-diagnostics--flycheck-enable
-    (if flycheck-checker
-        ;; Respect file/dir/explicit user-defined `flycheck-checker'.
-        (let ((old-checker flycheck-checker))
-          (apply orig-fn args)
-          (setq-local flycheck-checker old-checker))
-      (apply orig-fn args)))
-
   (add-hook! 'lsp-mode-hook
     (defun +lsp-display-guessed-project-root-h ()
       "Log what LSP things is the root of the current project."
@@ -107,7 +60,7 @@ should be a deliberate act (as is flipping this variable).")
         (if-let (root (lsp--calculate-root (lsp-session) path))
             (lsp--info "Guessed project root is %s" (abbreviate-file-name root))
           (lsp--info "Could not guess project root."))))
-    #'+lsp-init-optimizations-h)
+    #'+lsp-optimization-mode)
 
   (add-hook! 'lsp-completion-mode-hook
     (defun +lsp-init-company-backends-h ()
@@ -128,7 +81,8 @@ server getting expensively restarted when reverting buffers."
             restart
             (null +lsp-defer-shutdown)
             (= +lsp-defer-shutdown 0))
-        (funcall orig-fn restart)
+        (prog1 (funcall orig-fn restart)
+          (+lsp-optimization-mode -1))
       (when (timerp +lsp--deferred-shutdown-timer)
         (cancel-timer +lsp--deferred-shutdown-timer))
       (setq +lsp--deferred-shutdown-timer
@@ -137,7 +91,8 @@ server getting expensively restarted when reverting buffers."
              nil (lambda (workspace)
                    (let ((lsp--cur-workspace workspace))
                      (unless (lsp--workspace-buffers lsp--cur-workspace)
-                       (funcall orig-fn))))
+                       (funcall orig-fn)
+                       (+lsp-optimization-mode -1))))
              lsp--cur-workspace)))))
 
 

modules/tools/lsp/README.org

@@ -7,7 +7,6 @@
 - [[#description][Description]]
   - [[#module-flags][Module Flags]]
   - [[#plugins][Plugins]]
-  - [[#hacks][Hacks]]
 - [[#prerequisites][Prerequisites]]
 - [[#features][Features]]
   - [[#lsp-powered-project-search][LSP-powered project search]]
@@ -70,23 +69,17 @@ As of this writing, this is the state of LSP support in Doom Emacs:
 + [[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
-  that it is better etiquette to let the user decide when their development
-  environment is modified. Use ~M-x lsp-install-server~ to install LSP servers
-  manually.
-
 * Prerequisites
-This module has no direct prerequisites, but major-modes require you to install
+This module has no direct prerequisites, but different languages will need
-language servers.
+different language servers, which =lsp-mode= will prompt you to auto-install.
+=eglot= will not.
 
-You'll find a table that lists available language servers and how to install
+A table that lists available language servers and how to install them can be
-them [[https://github.com/emacs-lsp/lsp-mode#supported-languages][in the lsp-mode project README]]. The documentation of the module for your
+found [[https://emacs-lsp.github.io/lsp-mode/page/languages/][on 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]].
+For eglot users, a list of [[https://github.com/joaotavora/eglot/blob/master/README.md#connecting-to-a-server][default servers supported is on Eglot's README]],
-There is also instructions to add another server easily.
+including instructions to register your own.
 
 * TODO Features
 ** LSP-powered project search

modules/tools/lsp/config.el

@@ -12,20 +12,31 @@ killing and opening many LSP/eglot-powered buffers.")
 ;;
 ;;; Common
 
-(defun +lsp-init-optimizations-h ()
+(defvar +lsp--default-read-process-output-max nil)
-  "Deploys universal optimizations for `lsp-mode' and `eglot'."
+(defvar +lsp--default-gcmh-high-cons-threshold nil)
-  (when (or (bound-and-true-p eglot--managed-mode)
+
-            (bound-and-true-p lsp-mode))
+(define-minor-mode +lsp-optimization-mode
-    ;; `read-process-output-max' is only available on recent development
+  "Deploys universal GC and IPC optimizations for `lsp-mode' and `eglot'."
-    ;; builds of Emacs 27 and above.
+  :global t
-    (setq-local read-process-output-max (* 1024 1024))
+  :init-value nil
-    ;; REVIEW LSP causes a lot of allocations, with or without Emacs 27+'s
+  (if +lsp-optimization-mode
-    ;;        native JSON library, so we up the GC threshold to stave off
+      (progn
-    ;;        GC-induced slowdowns/freezes. Doom uses `gcmh' to enforce its GC
+        (setq +lsp--default-read-process-output-max
-    ;;        strategy, so we modify its variables rather than
+              (default-value 'read-process-output-max)
-    ;;        `gc-cons-threshold' directly.
+              +lsp--default-gcmh-high-cons-threshold
-    (setq-local gcmh-high-cons-threshold (* 2 (default-value 'gcmh-high-cons-threshold)))
+              (default-value 'gcmh-high-cons-threshold))
-    (gcmh-set-high-threshold)))
+        ;; `read-process-output-max' is only available on recent development
+        ;; builds of Emacs 27 and above.
+        (setq-default read-process-output-max (* 1024 1024))
+        ;; REVIEW LSP causes a lot of allocations, with or without Emacs 27+'s
+        ;;        native JSON library, so we up the GC threshold to stave off
+        ;;        GC-induced slowdowns/freezes. Doom uses `gcmh' to enforce its
+        ;;        GC strategy, so we modify its variables rather than
+        ;;        `gc-cons-threshold' directly.
+        (setq-default gcmh-high-cons-threshold (* 2 +lsp--default-gcmh-high-cons-threshold)))
+    (setq-default read-process-output-max +lsp--default-read-process-output-max
+                  gcmh-high-cons-threshold +lsp--default-gcmh-high-cons-threshold))
+  (gcmh-set-high-threshold))
 
 
 ;;