Merge pull request #163 from Wilfred/preserve_point_rustfmt

Correctly restore point position after running rustfmt

Author: nikomatsakis

rust-mode-tests.el

@@ -2561,6 +2561,18 @@ Fontification needs to include this whole string or none of it.
     )
   )
 
+(ert-deftest rust-test-revert-hook-preserves-point ()
+  (with-temp-buffer
+    ;; Insert some code, and put point in the middle.
+    (insert "fn foo() {}\n")
+    (insert "fn bar() {}\n")
+    (insert "fn baz() {}\n")
+    (goto-char (point-min))
+    (forward-line 1)
+    (let ((initial-point (point)))
+      (rust--after-revert-hook)
+      (should (equal initial-point (point))))))
+
 ;; If electric-pair-mode is available, load it and run the tests that use it.  If not,
 ;; no error--the tests will be skipped.
 (require 'elec-pair nil t)

rust-mode.el

@@ -1270,10 +1270,16 @@ This is written mainly to be used as `end-of-defun-function' for Rust."
   (unless (executable-find rust-rustfmt-bin)
     (error "Could not locate executable \"%s\"" rust-rustfmt-bin))
 
-  (let ((cur-point (point))
+  (let ((cur-line (line-number-at-pos))
+        (cur-column (current-column))
         (cur-win-start (window-start)))
     (rust--format-call (current-buffer))
-    (goto-char cur-point)
+    ;; Move to the same line and column as before.  This is best
+    ;; effort: if rustfmt inserted lines before point, we end up in
+    ;; the wrong place. See issue #162.
+    (goto-char (point-min))
+    (forward-line (1- cur-line))
+    (forward-char cur-column)
     (set-window-start (selected-window) cur-win-start))
 
   ;; Issue #127: Running this on a buffer acts like a revert, and could cause
@@ -1365,9 +1371,10 @@ This is written mainly to be used as `end-of-defun-function' for Rust."
   ;; to use `font-lock-ensure', which doesn't exist in Emacs 24 and earlier.
   ;; If it's not available, fall back to calling `font-lock-fontify-region'
   ;; on the whole buffer.
-  (if (fboundp 'font-lock-ensure)
-      (font-lock-ensure)
-    (font-lock-fontify-region (point-min) (point-max))))
+  (save-excursion
+    (if (fboundp 'font-lock-ensure)
+        (font-lock-ensure)
+      (font-lock-fontify-region (point-min) (point-max)))))
 
 (defun rust--before-save-hook ()
   (when rust-format-on-save (rust-format-buffer)))