introduce a new compilation-mode for rust-format

Changelog.md

@@ -1,6 +1,7 @@
 # Unreleased
 
 - Update rustfmt's defaults to use 2021 edition ([#554](https://github.com/rust-lang/rust-mode/issues/509)).
+- Introduce `rust-format-mode` for `rust-format-buffer` ([#556](https://github.com/rust-lang/rust-mode/pull/556)).
 
 # v1.0.6
 

rust-cargo-tests.el

@@ -1,5 +1,6 @@
 ;;; rust-cargo-tests.el --- ERT tests for rust-cargo.el  -*- lexical-binding: t; -*-
 (require 'rust-cargo)
+(require 'rust-rustfmt)
 (require 'ert)
 
 (defun rust-test--wait-process-exit ()
@@ -51,3 +52,21 @@
      (rust-test--send-process-string "1234\n")
      (rust-test--wait-process-exit)
      (should (rust-test--find-string "***run interactive: 1234")))))
+
+(ert-deftest rust-test-rustfmt ()
+  (skip-unless (executable-find "rustfmt"))
+  (rust-test--with-main-file-buffer
+   (let ((old-content (buffer-string))
+             (ret (rust-format-buffer)))
+         (should (string= ret "Formatted buffer with rustfmt."))
+         (should (string= old-content (buffer-string))))))
+
+(ert-deftest rust-test-rustfmt-parsing-errors ()
+  (skip-unless (executable-find "rustfmt"))
+  (with-temp-buffer
+    (insert "fn main() {")
+    (rust-format-buffer)
+    (with-current-buffer "*rustfmt*"
+      (should (eq major-mode 'rust-format-mode))
+      (should (rust-test--find-string "error:")))
+    (kill-buffer "*rustfmt*")))

rust-rustfmt.el

@@ -7,6 +7,9 @@
 ;;; Code:
 ;;; Options
 
+(require 'rust-compile)
+(require 'compile)
+
 (defcustom rust-format-on-save nil
   "Format future rust buffers before saving using rustfmt."
   :type 'boolean
@@ -39,6 +42,34 @@
 
 (defconst rust-rustfmt-buffername "*rustfmt*")
 
+(define-compilation-mode rust-format-mode "rust-format"
+  "Major mode for Rust compilation output."
+
+  (setq-local compilation-error-regexp-alist-alist nil)
+  (add-to-list 'compilation-error-regexp-alist-alist
+               (cons 'rustc-refs rustc-refs-compilation-regexps))
+  (add-to-list 'compilation-error-regexp-alist-alist
+               (cons 'rustc rustc-compilation-regexps))
+  (add-to-list 'compilation-error-regexp-alist-alist
+               (cons 'rustc-colon rustc-colon-compilation-regexps))
+  (add-to-list 'compilation-error-regexp-alist-alist
+               (cons 'cargo cargo-compilation-regexps))
+  (add-to-list 'compilation-error-regexp-alist-alist
+               (cons 'rustc-panics rustc-panics-compilation-regexps))
+
+  (setq-local compilation-error-regexp-alist nil)
+  (add-to-list 'compilation-error-regexp-alist 'rustc-refs)
+  (add-to-list 'compilation-error-regexp-alist 'rustc)
+  (add-to-list 'compilation-error-regexp-alist 'rustc-colon)
+  (add-to-list 'compilation-error-regexp-alist 'cargo)
+  (add-to-list 'compilation-error-regexp-alist 'rustc-panics)
+
+  (add-hook 'next-error-hook #'rustc-scroll-down-after-next-error)
+
+  (if (or compilation-auto-jump-to-first-error
+          (eq compilation-scroll-output 'first-error))
+      (set (make-local-variable 'compilation-auto-jump-to-next) t)))
+
 (defun rust--format-call (buf)
   "Format BUF using rustfmt."
   (let ((path exec-path))
@@ -69,10 +100,20 @@
                         (with-current-buffer buf
                           (replace-buffer-contents rust-rustfmt-buffername))
                       (copy-to-buffer buf (point-min) (point-max))))
-	        (let ((win (get-buffer-window rust-rustfmt-buffername)))
-		  (if win
-		      (quit-window t win)
-		    (kill-buffer rust-rustfmt-buffername))))
+                (let ((win (get-buffer-window rust-rustfmt-buffername)))
+                  (if win
+                      (quit-window t win)
+                    (kill-buffer rust-rustfmt-buffername))))
+               ((= ret 1)
+                (erase-buffer)
+                (insert-file-contents tmpf)
+
+                (rust-format-mode) ;; render compilation errors in compilation-mode
+                (setq-local compile-command (format "%s %s" rust-rustfmt-bin (buffer-file-name buf)))
+
+                (rust--format-fix-rustfmt-buffer (buffer-name buf))
+                (error "Rustfmt failed because of parsing errors, see %s buffer for details"
+                       rust-rustfmt-buffername))
                ((= ret 3)
                 (if (not (string= (buffer-string)
                                   (with-current-buffer buf (buffer-string))))