Add used language names to front of list

Previously, when a truly new language was used, it was added to the
front of the list as returned by `markdown-gfm-get-corpus`.  However,
when a known language was used it was simply kept in position in the
list of recognized languages. This yielded unexpected results with ido,
helm, etc. Now, we add all used languages to the history list
`markdown-gfm-used-languages`.  This list is then prepended to the list
of recognized languages and returned by `markdown-gfm-get-corpus`.

markdown-mode.el

@@ -3812,17 +3812,11 @@ if three backquotes inserted at the beginning of line."
     "Web-Ontology-Language" "WebIDL" "X10" "XC" "XML" "XPages" "XProc" "XQuery"
     "XS" "XSLT" "Xojo" "Xtend" "YAML" "Yacc" "Zephir" "Zimpl" "desktop" "eC" "edn"
     "fish" "mupad" "nesC" "ooc" "reStructuredText" "wisp" "xBase")
-  "Language specifiers recognized by github's syntax highlighting features.")
+  "Language specifiers recognized by GitHub's syntax highlighting features.")
 
 (defvar markdown-gfm-used-languages nil
-  "Languages in GFM code blocks which are not explicitly declared.
-Known language are declared in
-`markdown-gfm-recognized-languages' and
-`markdown-gfm-additional-languages'.")
+  "Language names used in GFM code blocks.")
 (make-variable-buffer-local 'markdown-gfm-used-languages)
-(defvar markdown-gfm-last-used-language nil
-  "Last language used in the current buffer in GFM code blocks.")
-(make-variable-buffer-local 'markdown-gfm-last-used-language)
 
 (defun markdown-trim-whitespace (str)
   (markdown-replace-regexp-in-string
@@ -3847,13 +3841,10 @@ Known language are declared in
      (if markdown-gfm-downcase-languages (cl-mapcar #'downcase given-corpus)
        given-corpus))))
 
-(defun markdown-add-language-if-new (lang)
-  (let* ((cleaned-lang (markdown-clean-language-string lang))
-         (find-result
-          (cl-find cleaned-lang (markdown-gfm-get-corpus)
-                   :test #'equal)))
-    (setq markdown-gfm-last-used-language cleaned-lang)
-    (unless find-result (push cleaned-lang markdown-gfm-used-languages))))
+(defun markdown-gfm-add-used-language (lang)
+  "Clean LANG and add to list of used languages."
+  (add-to-list 'markdown-gfm-used-languages
+               (markdown-clean-language-string lang)))
 
 (defun markdown-insert-gfm-code-block (&optional lang)
   "Insert GFM code block for language LANG.
@@ -3867,12 +3858,12 @@ automatically in order to have the correct markup."
                (markdown-clean-language-string
                 (completing-read
                  (format "Programming language [%s]: "
-                         (or markdown-gfm-last-used-language "none"))
+                         (or (car markdown-gfm-used-languages) "none"))
                  (markdown-gfm-get-corpus)
                  nil 'confirm nil
                  'markdown-gfm-language-history))
              (quit "")))))
-  (unless (string= lang "") (markdown-add-language-if-new lang))
+  (unless (string= lang "") (markdown-gfm-add-used-language lang))
   (when (> (length lang) 0) (setq lang (concat " " lang)))
   (if (markdown-use-region-p)
       (let ((b (region-beginning)) (e (region-end)))
@@ -3911,7 +3902,7 @@ automatically in order to have the correct markup."
                       (when (and (match-beginning 2) (match-end 2))
                         (buffer-substring-no-properties
                          (match-beginning 2) (match-end 2)))))
-       do (progn (when lang (markdown-add-language-if-new lang))
+       do (progn (when lang (markdown-gfm-add-used-language lang))
                  (goto-char (next-single-property-change (point) prop)))))))
 
 

tests/markdown-test.el

@@ -3741,6 +3741,8 @@ Detail: https://github.com/jrblevin/markdown-mode/issues/79"
   (markdown-test-string-gfm "line 1\nline 2\n"
    (end-of-line)
    (markdown-insert-gfm-code-block "elisp")
+   (should (equal (car markdown-gfm-used-languages) "elisp"))
+   (should (equal (car (markdown-gfm-get-corpus)) "elisp"))
    (should (string-equal (buffer-string)
                          "line 1\n\n``` elisp\n\n```\n\nline 2\n")))
   ;; Test with active region
@@ -3760,12 +3762,14 @@ Detail: https://github.com/jrblevin/markdown-mode/issues/79"
     (markdown-gfm-parse-buffer-for-languages)
     (should (equal markdown-gfm-used-languages
                    (list "MaDeUp" "LANGUAGES" "MADEUP")))
-    (should (equal markdown-gfm-last-used-language "MaDeUp"))
+    (should (equal (car markdown-gfm-used-languages) "MaDeUp"))
+    (should (equal (car (markdown-gfm-get-corpus)) "MaDeUp"))
     (goto-char (point-max))
     (markdown-insert-gfm-code-block "newlang")
     (should (equal markdown-gfm-used-languages
                    (list "newlang" "MaDeUp" "LANGUAGES" "MADEUP")))
-    (should (equal markdown-gfm-last-used-language "newlang"))
+    (should (equal (car markdown-gfm-used-languages) "newlang"))
+    (should (equal (car (markdown-gfm-get-corpus)) "newlang"))
     (let ((markdown-gfm-downcase-languages nil))
       (should
        (equal (markdown-gfm-get-corpus)