lang/rust: refactor racer config + add +rust/install-racer command (WIP)

modules/lang/rust/autoload.el

@@ -0,0 +1,11 @@
+;;; lang/rust/autoload.el
+
+;;;###autoload
+(defun +rust/install-racer ()
+  "Install and compile racer server."
+  (interactive)
+  (let ((racer-dir (expand-file-name "racer" +rust-cache-dir)))
+    (doom-fetch :github "rust-lang/rust.git" (expand-file-name "rust" +rust-cache-dir))
+    (doom-fetch :github "phildawes/racer.git" racer-dir)
+    (let ((default-directory racer-dir))
+      (doom-sh "cargo build --release"))))

modules/lang/rust/config.el

@@ -1,5 +1,8 @@
 ;;; module-rust.el
 
+(defvar +rust-cache-dir (concat doom-cache-dir "+rust/")
+  "TODO")
+
 (@def-package rust-mode
   :mode "\\.rs$"
   :init
@@ -9,14 +12,15 @@
          '+rust-is-cargo-project-p '+rust/cargo-run))
 
 
-(defvar racer-cmd (concat doom-cache-dir "racer"))
-(defvar racer-rust-src-path (concat doom-cache-dir "rust/src/"))
 (@def-package racer
   :after rust-mode
-  :when (file-exists-p racer-cmd)
+  :preface
   :init
   (@add-hook rust-mode '(racer-mode eldoc-mode flycheck-rust-setup))
   :config
+  (setq racer-cmd (expand-file-name "racer/target/release/racer" +rust-cache-dir)
+        racer-rust-src-path (expand-file-name "rust/src/" +rust-cache-dir))
+
   ;; TODO Unit test keybinds
   (@set :company-backend 'rust-mode '(company-racer))
   (@map :map rust-mode-map :m "gd" 'racer-find-definition))