fix(flyspell-and-abbrev): stop re-scanning the whole buffer on every C-'

cj/flyspell-then-abbrev ran a bare flyspell-buffer guarded by (unless flyspell-mode ...), but nothing turned flyspell-mode on, so the guard never tripped. Every C-' press re-scanned the whole buffer, which is O(buffer) per keypress in large files. I routed the scan through cj/flyspell-on-for-buffer-type instead, so the mode sticks after the first press and the buffer is scanned once.

2 files changed, 26 insertions, 3 deletions

diff --git a/modules/flyspell-and-abbrev.el b/modules/flyspell-and-abbrev.el
index b73bfdf3..ebe4898e 100644
--- a/modules/flyspell-and-abbrev.el
+++ b/modules/flyspell-and-abbrev.el
@@ -197,9 +197,10 @@ Without prefix argument, it's created in the global abbrev table.
 Press C-' repeatedly to step through misspellings one at a time."
   (interactive "P")
   (cj/--require-spell-checker)
-  ;; Run flyspell-buffer only if buffer hasn't been checked yet
-  (unless (bound-and-true-p flyspell-mode)
-    (flyspell-buffer))
+  ;; Enable Flyspell for the buffer type so the mode sticks and the buffer is
+  ;; scanned once.  A bare flyspell-buffer here never turned the mode on, so
+  ;; the guard never tripped and every C-' press re-scanned the whole buffer.
+  (cj/flyspell-on-for-buffer-type)
 
   (let ((misspelled-word (cj/flyspell-goto-previous-misspelling (point))))
     (if (not misspelled-word)
diff --git a/tests/test-flyspell-and-abbrev.el b/tests/test-flyspell-and-abbrev.el
index ef8cc637..3b494d5e 100644
--- a/tests/test-flyspell-and-abbrev.el
+++ b/tests/test-flyspell-and-abbrev.el
@@ -97,5 +97,27 @@
         (cj/flyspell-on-for-buffer-type)))
     (should mode-called)))
 
+;; --------------------------- cj/flyspell-then-abbrev -------------------------
+
+(ert-deftest test-flyspell-then-abbrev-enables-mode-not-bare-rescan ()
+  "Regression: cj/flyspell-then-abbrev routes the initial scan through
+cj/flyspell-on-for-buffer-type, which enables flyspell-mode so it sticks.
+The bare flyspell-buffer it replaced never turned the mode on, so the guard
+never tripped and every C-' press re-scanned the whole buffer (O(buffer) per
+keypress in large files)."
+  (let (on-called scan-called)
+    (cl-letf (((symbol-function 'cj/--require-spell-checker) #'ignore)
+              ((symbol-function 'cj/flyspell-on-for-buffer-type)
+               (lambda () (setq on-called t)))
+              ((symbol-function 'flyspell-buffer)
+               (lambda (&rest _) (setq scan-called t)))
+              ((symbol-function 'cj/flyspell-goto-previous-misspelling)
+               (lambda (&rest _) nil)))
+      (with-temp-buffer
+        (text-mode)
+        (cj/flyspell-then-abbrev nil)))
+    (should on-called)
+    (should-not scan-called)))
+
 (provide 'test-flyspell-and-abbrev)
 ;;; test-flyspell-and-abbrev.el ends here