small fixes

Author: Danny McClanahan

markdown-mode.el

@@ -1075,12 +1075,12 @@ update the buffer containing the preview and return the buffer."
   :type 'function)
 
 (defcustom markdown-live-preview-delete-export 'delete-on-destroy
-  "Delete exported html file when using `markdown-live-preview-sync-export' on every
+  "Delete exported html file when using `markdown-live-preview-mode' on every
 export by setting to 'delete-on-export, when quitting
 `markdown-live-preview-mode' by setting to 'delete-on-destroy, or not at all
 when nil."
   :group 'markdown
-  :type 'symbol)
+  :type '(symbol :validate markdown-live-preview-validate-delete-export))
 
 (defcustom markdown-live-preview-idle-delay 1
   "Delay to wait idle before refreshing `markdown-live-preview-mode' output."
@@ -5296,6 +5296,13 @@ current filename, but with the extension removed and replaced with .html."
 
 ;;; Live Preview ===============================================================
 
+(defun markdown-live-preview-validate-delete-export (widget)
+  (let ((sym (widget-value widget)))
+    (unless (memq sym '(delete-on-export delete-on-destroy nil))
+      (widget-put widget :error (format "Invalid value: '%s'"
+                                        (symbol-name sym)))
+      widget)))
+
 (defvar markdown-live-preview-view-buffer nil
   "Buffer used to preview markdown output in
 `markdown-live-preview-sync-export' and `markdown-live-preview-async-export'.")
@@ -5545,8 +5552,8 @@ output buffer in another window."
 (defun markdown-live-preview-re-export ()
   (interactive)
   "If the current buffer is a buffer displaying the exported version of a
-`markdown-live-preview-mode' buffer, call `markdown-live-preview-sync-export'
-and update this buffer's contents."
+`markdown-live-preview-mode' buffer, call `markdown-live-preview-async-export'
+or `markdown-live-preview-sync-export' and update this buffer's contents."
   (when markdown-live-preview-source-buffer
     (with-current-buffer markdown-live-preview-source-buffer
       (if markdown-live-preview-current-buffer-sync-async