Merge pull request #342 from brotzeit/flycheck-check-toolchain

automatically detect toolchain and use correct clippy params

README.md

@@ -483,7 +483,7 @@ it with `rustup component add --toolchain nightly clippy`.
 
 ### Flycheck
 
-In case you want to see clippy lints with flycheck, you can activate
+In case you want to use clippy with flycheck but without LSP, you can activate
 this checker and use the command `flycheck-list-errors`
 
 ```elisp
@@ -496,15 +496,12 @@ Turn off flycheck.
 (remove-hook 'rustic-mode-hook 'flycheck-mode)
 ```
 
-The parameters of the checker can be modified with `rustic-flycheck-clippy-params`
-and are by default configured for using unstable options that are only available
-on the nightly toolchains.
+The checker automatically detects the active toolchain and applies the
+correct parameters You can set a default value for both stable and
+nightly toolchains. These are the default values.
 
-If you are using the stable toolchain you have to change the value:
-
-```elisp
-(setq rustic-flycheck-clippy-params "--message-format=json")
-```
+- `rustic-flycheck-clippy-params-stable` "--message-format=json"
+- `rustic-flycheck-clippy-params-nightly` "--message-format=json -Zunstable-options"
 
 ### lsp-mode
 

rustic-flycheck.el

@@ -9,8 +9,13 @@
 
 (require 'rustic)
 
-(defcustom rustic-flycheck-clippy-params "--message-format=json -Zunstable-options"
-  "Parameters for the flycheck clippy checker `rustic-clippy'."
+(defcustom rustic-flycheck-clippy-params-stable "--message-format=json"
+  "Parameters for the flycheck clippy checker `rustic-clippy' when active toolchain is stable."
+  :type 'string
+  :group 'rustic-flycheck)
+
+(defcustom rustic-flycheck-clippy-params-nightly "--message-format=json -Zunstable-options"
+  "Parameters for the flycheck clippy checker `rustic-clippy' when active toolchain is nightly."
   :type 'string
   :group 'rustic-flycheck)
 
@@ -160,11 +165,22 @@ Flycheck according to the Cargo project layout."
         (setq-local flycheck-rust-crate-type .kind)
         (setq-local flycheck-rust-binary-name .name)))))
 
+(defun rustic-flycheck-nightly-p ()
+  "Check if active toolchain is a nightly toolchain."
+  (let ((tc (shell-command-to-string "rustup show active-toolchain")))
+    (string-match-p "^nightly" (car (split-string tc)))))
+
+(defun rustic-flycheck-clippy-params ()
+  "Return clippy parameters for flycheck depending on the active toolchain."
+  (if (rustic-flycheck-nightly-p)
+      rustic-flycheck-clippy-params-nightly
+    rustic-flycheck-clippy-params-stable))
+
 (flycheck-define-checker rustic-clippy
   "A Rust syntax checker using clippy.
 
 See URL `https://github.com/rust-lang-nursery/rust-clippy'."
-  :command ("cargo" "clippy" (eval (split-string rustic-flycheck-clippy-params)))
+  :command ("cargo" "clippy" (eval (split-string (rustic-flycheck-clippy-params))))
   :error-parser flycheck-parse-cargo-rustc
   :error-filter flycheck-rust-error-filter
   :error-explainer flycheck-rust-error-explainer