Add new ispell-change-dictionary-hook (Bug#1110)

* lisp/textmodes/ispell.el (ispell-change-dictionary-hook): New hook.
(ispell-change-dictionary): Call new hook (bug#1110).

etc/NEWS

@@ -1630,6 +1630,14 @@ When non-nil, watch whether the bookmark file has changed on disk.
 This library generates manual C++ template instantiations.  It should
 no longer be useful on modern compilers, which do this automatically.
 
+** Ispell
+
+---
+*** New hook 'ispell-change-dictionary-hook'.
+This runs after changing the dictionary and could be used to
+automatically spellcheck a buffer when changing language without
+needing to advice 'ispell-change-dictionary'.
+
 
 * New Modes and Packages in Emacs 27.1
 

lisp/textmodes/ispell.el

@@ -2973,6 +2973,9 @@ With CLEAR, buffer session localwords are cleaned."
     (message "Ispell process killed")
     nil))
 
+(defvar ispell-change-dictionary-hook nil
+  "Hook run after changing dictionary.")
+
 ;; ispell-change-dictionary is set in some people's hooks.  Maybe this should
 ;;  call ispell-init-process rather than wait for a spell checking command?
 
@@ -2998,7 +3001,8 @@ By just answering RET you can find out what the current dictionary is."
 	 (ispell-internal-change-dictionary)
 	 (message "Using %s dictionary"
 		  (or (and (not arg) ispell-local-dictionary)
-		      ispell-dictionary "default")))
+		      ispell-dictionary "default"))
+         (run-hooks 'ispell-change-dictionary-hook))
 	((equal dict (or (and (not arg) ispell-local-dictionary)
 			 ispell-dictionary "default"))
 	 ;; Specified dictionary is the default already. Could reload
@@ -3020,7 +3024,8 @@ By just answering RET you can find out what the current dictionary is."
 	 (setq ispell-buffer-session-localwords nil)
 	 (message "%s Ispell dictionary set to %s"
 		  (if arg "Global" "Local")
-		  dict))))
+		  dict)
+         (run-hooks 'ispell-change-dictionary-hook))))
 
 (defun ispell-internal-change-dictionary ()
   "Update the dictionary and the personal dictionary used by Ispell.