Add Enchant support to ispell.el (Bug#17742)

* lisp/textmodes/ispell.el (ispell-program-name): Add “enchant”.
(ispell-really-enchant): Add variable.
(ispell-check-version): If using Enchant, check it’s new enough (at
least 1.6.1).  (Like the ispell check, this is absolute: cannot work
without.)
(ispell-enchant-dictionary-alist): Add variable.
(ispell-find-enchant-dictionaries): Add function, based on
ispell-find-aspell-dictionaries.
(ispell-set-spellchecker-params): Allow dictionary auto-detection for
Enchant, and call ispell-find-enchant-dictionaries to find them.  Use
old ispell name to locale mapping code for Enchant too.
(ispell-send-replacement): Make it work with Enchant.

lisp/textmodes/ispell.el

@@ -208,6 +208,10 @@ Must be greater than 1."
   :type 'integer
   :group 'ispell)
 
+;; XXX Add enchant to this list once enchant >= 1.6.1 is widespread.
+;; Before that, adding it is useless, as if it is found, it will just
+;; cause an error; and one of the other spelling engines below is
+;; almost certainly installed in any case, for enchant to use.
 (defcustom ispell-program-name
   (or (executable-find "aspell")
       (executable-find "ispell")
@@ -605,6 +609,8 @@ english.aff).  Aspell and Hunspell don't have this limitation.")
   "Non-nil if we can use Aspell extensions.")
 (defvar ispell-really-hunspell nil
   "Non-nil if we can use Hunspell extensions.")
+(defvar ispell-really-enchant nil
+  "Non-nil if we can use Enchant extensions.")
 (defvar ispell-encoding8-command nil
   "Command line option prefix to select encoding if supported, nil otherwise.
 If setting the encoding is supported by spellchecker and is selectable from
@@ -739,17 +745,26 @@ Otherwise returns the library directory name, if that is defined."
 		  (and (search-forward-regexp
 			"(but really Hunspell \\([0-9]+\\.[0-9\\.-]+\\)?)"
                         nil t)
+		       (match-string 1)))
+            (setq ispell-really-enchant
+		  (and (search-forward-regexp
+			"(but really Enchant \\([0-9]+\\.[0-9\\.-]+\\)?)"
+                        nil t)
 		       (match-string 1)))))
 
       (let* ((aspell8-minver   "0.60")
              (ispell-minver    "3.1.12")
              (hunspell8-minver "1.1.6")
+             (enchant-minver   "1.6.1")
              (minver (cond
                       ((not (version<= ispell-minver ispell-program-version))
                        ispell-minver)
                       ((and ispell-really-aspell
                             (not (version<= aspell8-minver ispell-really-aspell)))
-                       aspell8-minver))))
+                       aspell8-minver)
+                      ((and ispell-really-enchant
+                            (not (version<= enchant-minver ispell-really-enchant)))
+                       enchant-minver))))
 
         (if minver
 	    (error "%s release %s or greater is required"
@@ -1183,6 +1198,36 @@ dictionary from that list was found."
                     (list dict))
                   ispell-hunspell-dictionary-alist :test #'equal))))
 
+;; Make ispell.el work better with enchant.
+
+(defvar ispell-enchant-dictionary-alist nil
+  "An alist of parsed Enchant dicts and associated parameters.
+Internal use.")
+
+(defun ispell-find-enchant-dictionaries ()
+  "Find Enchant's dictionaries, and record in `ispell-enchant-dictionary-alist'."
+  (let* ((dictionaries
+	  (split-string
+	   (with-temp-buffer
+	     (ispell-call-process
+              (concat ispell-program-name "-lsmod") nil t nil "-list-dicts")
+	     (buffer-string))
+           " ([^)]+)\n"))
+         (found
+          (mapcar #'(lambda (lang)
+                      `(,lang "[[:alpha:]]" "[^[:alpha:]]" "['.’-]" t nil nil utf-8))
+                  dictionaries)))
+    ;; Merge into FOUND any elements from the standard ispell-dictionary-base-alist
+    ;; which have no element in FOUND at all.
+    (dolist (dict ispell-dictionary-base-alist)
+      (unless (assoc (car dict) found)
+	(setq found (nconc found (list dict)))))
+    (setq ispell-enchant-dictionary-alist found)
+    ;; Add a default entry
+    (let ((default-dict
+           '(nil "[[:alpha:]]" "[^[:alpha:]]" "['.’-]" t nil nil utf-8)))
+      (push default-dict ispell-enchant-dictionary-alist))))
+
 ;; Set params according to the selected spellchecker
 
 (defvar ispell-last-program-name nil
@@ -1208,7 +1253,7 @@ aspell is used along with Emacs).")
 		   (setq ispell-library-directory (ispell-check-version))
 		   t)
 	       (error nil))
-	     ispell-encoding8-command)
+	     (or ispell-encoding8-command ispell-really-enchant))
 	;; auto-detection will only be used if spellchecker is not
 	;; ispell and supports a way to set communication to UTF-8.
 	(if ispell-really-aspell
@@ -1216,11 +1261,14 @@ aspell is used along with Emacs).")
 		(ispell-find-aspell-dictionaries))
 	  (if ispell-really-hunspell
 	      (or ispell-hunspell-dictionary-alist
-		  (ispell-find-hunspell-dictionaries)))))
+		  (ispell-find-hunspell-dictionaries))
+            (if ispell-really-enchant
+                (or ispell-enchant-dictionary-alist
+                    (ispell-find-enchant-dictionaries))))))
 
     ;; Substitute ispell-dictionary-alist with the list of
     ;; dictionaries corresponding to the given spellchecker.
-    ;; If a recent aspell or hunspell, use the list of really
+    ;; With programs that support it, use the list of really
     ;; installed dictionaries and add to it elements of the original
     ;; list that are not present there. Allow distro info.
     (let ((found-dicts-alist
@@ -1229,17 +1277,19 @@ aspell is used along with Emacs).")
 		   ispell-aspell-dictionary-alist
 		 (if ispell-really-hunspell
 		     ispell-hunspell-dictionary-alist))
-	     nil))
+	     (if ispell-really-enchant
+                 ispell-enchant-dictionary-alist
+               nil)))
 	  (ispell-dictionary-base-alist ispell-dictionary-base-alist)
 	  ispell-base-dicts-override-alist ; Override only base-dicts-alist
 	  all-dicts-alist)
 
       ;; While ispell and aspell (through aliases) use the traditional
-      ;; dict naming originally expected by ispell.el, hunspell
-      ;; uses locale based names with no alias.  We need to map
+      ;; dict naming originally expected by ispell.el, hunspell & Enchant
+      ;; use locale-based names with no alias.  We need to map
       ;; standard names to locale based names to make default dict
-      ;; definitions available for hunspell.
-      (if ispell-really-hunspell
+      ;; definitions available to these programs.
+      (if (or ispell-really-hunspell ispell-really-enchant)
 	  (let (tmp-dicts-alist)
 	    (dolist (adict ispell-dictionary-base-alist)
 	      (let* ((dict-name (nth 0 adict))
@@ -1264,7 +1314,7 @@ aspell is used along with Emacs).")
 			(setq ispell-args
 			      (nconc ispell-args (list "-d" dict-equiv)))
 		      (message
-		       "ispell-set-spellchecker-params: Missing Hunspell equiv for \"%s\". Skipping."
+		       "ispell-set-spellchecker-params: Missing equivalent for \"%s\". Skipping."
 		       dict-name)
 		      (setq skip-dict t)))
 
@@ -1306,7 +1356,7 @@ aspell is used along with Emacs).")
                          (nth 4 adict)   ; many-otherchars-p
                          (nth 5 adict)   ; ispell-args
                          (nth 6 adict)   ; extended-character-mode
-                         (if ispell-encoding8-command
+                         (if (or ispell-encoding8-command ispell-really-enchant)
                              'utf-8
                            (nth 7 adict)))
                       adict)
@@ -1742,9 +1792,10 @@ and pass it the output of the last Ispell invocation."
 	    (erase-buffer)))))))
 
 (defun ispell-send-replacement (misspelled replacement)
-  "Notify Aspell that MISSPELLED should be spelled REPLACEMENT.
-This allows improving the suggestion list based on actual misspellings."
-  (and ispell-really-aspell
+  "Notify spell checker that MISSPELLED should be spelled REPLACEMENT.
+This allows improving the suggestion list based on actual misspellings.
+Only works for Aspell and Enchant."
+  (and (or ispell-really-aspell ispell-really-enchant)
        (ispell-send-string (concat "$$ra " misspelled "," replacement "\n"))))