From 1ede94c88a3b0d91f1c2923f8c75fc42aa93ba46 Mon Sep 17 00:00:00 2001
From: Sergei Nizovtsev <snizovtsev@gmail.com>
Date: Tue, 19 Aug 2025 16:29:26 +0200
Subject: [PATCH] feat(lsp): add `+booster` flag

Adds support for LSP IO performance booster. This may reduce UI-blocking
time in case of unresponsive LSP backend.
---
 modules/tools/lsp/+eglot.el   |  7 +++++++
 modules/tools/lsp/+lsp.el     | 18 +++++++++++++++++-
 modules/tools/lsp/doctor.el   |  4 ++++
 modules/tools/lsp/packages.el |  6 +++++-
 4 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/modules/tools/lsp/+eglot.el b/modules/tools/lsp/+eglot.el
index 0990f8a1e..badcd61dc 100644
--- a/modules/tools/lsp/+eglot.el
+++ b/modules/tools/lsp/+eglot.el
@@ -67,3 +67,10 @@ server an expensive restart when its buffer is reverted."
 (use-package! flycheck-eglot
   :when (modulep! :checkers syntax -flymake)
   :hook (eglot-managed-mode . flycheck-eglot-mode))
+
+(use-package! eglot-booster
+  :when (modulep! +eglot +booster)
+  :after eglot
+  :config (eglot-booster-mode)
+  :init
+  (setq eglot-booster-io-only t))
diff --git a/modules/tools/lsp/+lsp.el b/modules/tools/lsp/+lsp.el
index 2be1beee3..c7b4ed1ad 100644
--- a/modules/tools/lsp/+lsp.el
+++ b/modules/tools/lsp/+lsp.el
@@ -161,7 +161,23 @@ server getting expensively restarted when reverting buffers."
 
   (when (modulep! :completion corfu)
     (setq lsp-completion-provider :none)
-    (add-hook 'lsp-mode-hook #'lsp-completion-mode)))
+    (add-hook 'lsp-mode-hook #'lsp-completion-mode))
+
+  (when (modulep! +booster)
+    (defun lsp-booster--advice-final-command (old-fn cmd &optional test?)
+      "Prepend emacs-lsp-booster command to lsp CMD."
+      (let ((orig-result (funcall old-fn cmd test?)))
+        (if (and (not test?)                             ;; for check lsp-server-present?
+                 (not (file-remote-p default-directory)) ;; see lsp-resolve-final-command, it would add extra shell wrapper
+                 (not (functionp 'json-rpc-connection))  ;; native json-rpc
+                 (executable-find "emacs-lsp-booster"))
+            (progn
+              (when-let ((command-from-exec-path (executable-find (car orig-result))))  ;; resolve command from exec-path (in case not found in $PATH)
+                (setcar orig-result command-from-exec-path))
+              (message "Using emacs-lsp-booster for %s!" orig-result)
+              (append '("emacs-lsp-booster" "--disable-bytecode" "--") orig-result))
+          orig-result)))
+    (advice-add 'lsp-resolve-final-command :around #'lsp-booster--advice-final-command)))
 
 (use-package! lsp-ui
   :hook (lsp-mode . lsp-ui-mode)
diff --git a/modules/tools/lsp/doctor.el b/modules/tools/lsp/doctor.el
index 42c59f33c..9b67ae95c 100644
--- a/modules/tools/lsp/doctor.el
+++ b/modules/tools/lsp/doctor.el
@@ -6,3 +6,7 @@
 (unless (modulep! +eglot)
   (unless (executable-find "npm")
     (warn! "Couldn't find npm. `lsp-mode' needs npm to auto-install some LSP servers. For more information, see https://emacs-lsp.github.io/lsp-mode/page/languages/.")))
+
+(when (modulep! +booster)
+  (unless (executable-find "emacs-lsp-booster")
+    (warn! "Couldn't find emacs-lsp-booster executable.")))
diff --git a/modules/tools/lsp/packages.el b/modules/tools/lsp/packages.el
index 259b19714..1fc85b9f4 100644
--- a/modules/tools/lsp/packages.el
+++ b/modules/tools/lsp/packages.el
@@ -7,7 +7,11 @@
       (when (modulep! :completion vertico)
         (package! consult-eglot :pin "2816f8aad7d6a1e6d5e5b4a5e04c1d74b82b26b8"))
       (when (modulep! :checkers syntax -flymake)
-        (package! flycheck-eglot :pin "0d7f0afc9bf08fce4a3ee225ec6540a91f8cfd76")))
+        (package! flycheck-eglot :pin "0d7f0afc9bf08fce4a3ee225ec6540a91f8cfd76"))
+      (when (modulep! +booster)
+        (package! eglot-booster
+          :recipe (:host github :repo "jdtsmith/eglot-booster")
+          :pin "cab7803c4f0adc7fff9da6680f90110674bb7a22")))
   (package! lsp-mode :pin "65a414ddeb84d0282eda357cbd41ea674a42fd0b")
   (package! lsp-ui :pin "bbb1aa0192cce1ee39c2f36953cc5256d49534a4")
   (when (modulep! :completion ivy)