From 54e3d81b1fad94699eb1081d2b1276f5d72143fd Mon Sep 17 00:00:00 2001
From: Daniel Gerlach <Daniel.Gerlach1981@googlemail.com>
Date: Mon, 21 Nov 2022 21:14:15 +0100
Subject: [PATCH] Update rust module (#1388)

Use rust-analyzer as lsp server and tree-sitter for syntax highlighting.
---
 CHANGELOG.md            |  1 +
 docs/modules/rust.md    |  8 ++++++--
 modules/prelude-rust.el | 42 ++++++++++++++++++++++++++---------------
 3 files changed, 34 insertions(+), 17 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3815ecc..8f63d02 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,6 +20,7 @@
 * Replace `yank-pop` key-binding to `counse-yank-pop` for `ivy-mode`.
 * The keybinding for `proced` is now enabled unconditionally.
 * Replace prelude-go backend with `lsp` instead of unmaintained tools
+* Use `rust-analyzer` as language server for prelude-rust and provide nicer syntax highlighting with `tree-sitter`
 
 ### Bugs fixed
 
diff --git a/docs/modules/rust.md b/docs/modules/rust.md
index 3c88d35..c4cced0 100644
--- a/docs/modules/rust.md
+++ b/docs/modules/rust.md
@@ -12,8 +12,7 @@ following packages in your system:
 * `rustc` (Rust compiler)
 * `cargo` (Rust package manager)
 * `rustfmt` (Rust tool for formatting code)
-* `racer` (Rust completion tool, not necessary if `prelude-lsp` is enabled)
-* `rls` (Rust Language Server, if the `prelude-lsp` feature is enabled)
+* `rust-analyzer` (Rust Language Server, required for `prelude-lsp` feature)
 
 ## Rust Mode
 
@@ -21,6 +20,11 @@ Emacs comes with Rust programming support through the built-in
 `rust-mode`. Whenever you are editing Rust code run <kbd>C-h m</kbd> to
 look at the Rust mode key bindings.
 
+## Syntax highlighting
+
+[tree-sitter-mode](https://emacs-tree-sitter.github.io/) is used for nicer
+syntax highlighting.
+
 ## Syntax checking
 
 Prelude ships with [Flycheck](https://github.com/flycheck/flycheck),
diff --git a/modules/prelude-rust.el b/modules/prelude-rust.el
index dd20493..339d745 100644
--- a/modules/prelude-rust.el
+++ b/modules/prelude-rust.el
@@ -1,6 +1,6 @@
 ;;; prelude-rust.el --- Emacs Prelude: Rust programming support.
 ;;
-;; Authors: Doug MacEachern, Manoel Vilela, Ben Alex
+;; Authors: Doug MacEachern, Manoel Vilela, Ben Alex, Daniel Gerlach
 
 ;; This file is not part of GNU Emacs.
 
@@ -32,37 +32,49 @@
 ;; You may need to install the following packages on your system:
 ;; * rustc (Rust Compiler)
 ;; * cargo (Rust Package Manager)
-;; * racer (Rust Completion Tool)
 ;; * rustfmt (Rust Tool for formatting code)
-;; * rls (Rust Language Server, if the prelude-lsp feature is enabled)
+;; * rust-analyzer as lsp server needs to be in global path, see:
+;; https://rust-analyzer.github.io/manual.html#rust-analyzer-language-server-binary
+
 
 (prelude-require-packages '(rust-mode
                             cargo
                             flycheck-rust
+                            tree-sitter
+                            tree-sitter-langs
+                            yasnippet
                             ron-mode))
 
-(unless (featurep 'prelude-lsp)
-  (prelude-require-packages '(racer)))
-
-(setq rust-format-on-save t)
+(require 'tree-sitter)
+(require 'tree-sitter-langs)
 
 (with-eval-after-load 'rust-mode
   (add-hook 'rust-mode-hook 'cargo-minor-mode)
   (add-hook 'flycheck-mode-hook 'flycheck-rust-setup)
 
-  (if (featurep 'prelude-lsp)
-      (add-hook 'rust-mode-hook 'lsp)
-    (add-hook 'rust-mode-hook 'racer-mode)
-    (add-hook 'racer-mode-hook 'eldoc-mode))
+  ;; enable lsp for rust, by default it uses rust-analyzer as lsp server
+  (add-hook 'rust-mode-hook 'lsp)
+
+  ;; enable tree-sitter for nicer syntax highlighting
+  (add-hook 'rust-mode-hook #'tree-sitter-mode)
+  (add-hook 'rust-mode-hook #'tree-sitter-hl-mode)
 
   (defun prelude-rust-mode-defaults ()
-    (unless (featurep 'prelude-lsp)
-      (local-set-key (kbd "C-c C-d") 'racer-describe)
-      (local-set-key (kbd "C-c .") 'racer-find-definition)
-      (local-set-key (kbd "C-c ,") 'pop-tag-mark))
+    ;; format on save
+    (setq rust-format-on-save t)
+
+    ;; lsp settings
+    (setq
+     ;; enable macro expansion
+     lsp-rust-analyzer-proc-macro-enable t
+     lsp-rust-analyzer-experimental-proc-attr-macros t)
 
     ;; Prevent #! from chmodding rust files to be executable
     (remove-hook 'after-save-hook 'executable-make-buffer-file-executable-if-script-p)
+
+    ;; snippets are required for correct lsp autocompletions
+    (yas-minor-mode)
+
     ;; CamelCase aware editing operations
     (subword-mode +1))