Improve flyspell support

+ Make flyspell more selective about what to scan in markdown buffers.
+ Don't mark duplicates when proseline or langtool are present.
+ Add set-flyspell-predicate! for seeing mode-specific word predicates.

modules/lang/markdown/autoload.el

@@ -20,3 +20,23 @@
       (if (thing-at-point-looking-at +markdown--regex-del)
           (markdown-unwrap-thing-at-point nil 2 4)
         (markdown-wrap-or-insert delim delim 'word nil nil)))))
+
+;;;###autoload
+(defun +markdown-flyspell-word-p ()
+  "Return t if point is on a word that should be spell checked.
+
+Return nil if on a link url, markup, html, or references."
+  (let ((faces (doom-enlist (get-text-property (point) 'face))))
+    (or (and (memq 'font-lock-comment-face faces)
+             (memq 'markdown-code-face faces))
+        (not (cl-loop with unsafe-faces = '(markdown-reference-face
+                                            markdown-url-face
+                                            markdown-markup-face
+                                            markdown-comment-face
+                                            markdown-html-attr-name-face
+                                            markdown-html-attr-value-face
+                                            markdown-html-tag-name-face
+                                            markdown-code-face)
+                      for face in faces
+                      if (memq face unsafe-faces)
+                      return t)))))

modules/lang/markdown/config.el

@@ -17,6 +17,8 @@
         markdown-gfm-uppercase-checkbox t) ; for compat with org-mode
 
   :config
+  (set-flyspell-predicate! '(markdown-mode gfm-mode) #'+markdown-flyspell-word-p)
+
   (defun +markdown|set-fill-column-and-line-spacing ()
     (setq-local line-spacing 2)
     (setq-local fill-column 80))

modules/tools/flyspell/autoload.el

@@ -0,0 +1,16 @@
+;;; tools/flyspell/autoload.el -*- lexical-binding: t; -*-
+
+(defvar +flyspell--predicate-alist nil
+  "TODO")
+
+;;;###autodef
+(defun set-flyspell-predicate! (modes predicate)
+  "TODO"
+  (dolist (mode (doom-enlist modes) +flyspell--predicate-alist)
+    (add-to-list '+flyspell--predicate-alist (cons mode predicate))))
+
+;;;###autoload
+(defun +flyspell|init-predicate ()
+  "TODO"
+  (when-let* ((pred (assq major-mode +flyspell--predicate-alist)))
+    (setq-local flyspell-generic-check-word-predicate (cdr pred))))

modules/tools/flyspell/config.el

@@ -47,14 +47,27 @@ Since spellchecking can be slow in some buffers, this can be disabled with:
 
 
 ;; `flyspell' (built-in)
+(progn
   (setq flyspell-issue-welcome-flag nil)
 
+  (defun +flyspell|inhibit-duplicate-detection-maybe ()
+    "Don't mark duplicates when style/grammar linters are present.
+e.g. proselint and langtool."
+    (when (or (executable-find "proselint")
+              (featurep 'langtool))
+      (setq-local flyspell-mark-duplications-flag nil)))
+  (add-hook 'flyspell-mode-hook #'+flyspell|inhibit-duplicate-detection-maybe)
+
   (defun +flyspell|immediately ()
     "Spellcheck the buffer when `flyspell-mode' is enabled."
     (when (and flyspell-mode +flyspell-immediately)
       (flyspell-buffer)))
   (add-hook 'flyspell-mode-hook #'+flyspell|immediately)
 
+  ;; Ensure mode-local predicates declared with `set-flyspell-predicate!' are
+  ;; used in their respective major modes.
+  (add-hook 'flyspell-mode-hook #'+flyspell|init-predicate))
+
 
 (def-package! flyspell-correct
   :commands (flyspell-correct-word-generic