ob: new function to check header arguments for errors C-c C-v c

* doc/orgcard.tex: Adding line for org-babel-check-src-block.
* lisp/ob-keys.el (org-babel-key-bindings): Adding key sequence for
  org-babel-check-src-block.
* lisp/ob.el (org-babel-expand-src-block): Fit within 80 cols.
  (org-babel-edit-distance): Returns the edit distance of two strings.
  (org-babel-check-src-block): Check a code block for errors.

doc/orgcard.tex

@@ -443,6 +443,7 @@ formula, \kbd{:=} a field formula.
 
 \key{execute code block at point}{C-c C-c}
 \key{open results of code block at point}{C-c C-o}
+\key{check code block at point for errors}{C-c C-v c}
 \key{view expanded body of code block at point}{C-c C-v v}
 \key{go to named code block}{C-c C-v g}
 \key{go to named result}{C-c C-v r}

lisp/ob-keys.el

@@ -73,6 +73,8 @@ functions which are assigned key bindings, and see
     ("t" . org-babel-tangle)
     ("\C-f" . org-babel-tangle-file)
     ("f" . org-babel-tangle-file)
+    ("\C-c" . org-babel-check-src-block)
+    ("c" . org-babel-check-src-block)
     ("\C-l" . org-babel-load-in-session)
     ("l" . org-babel-load-in-session)
     ("\C-i" . org-babel-lob-ingest)

lisp/ob.el

@@ -461,14 +461,51 @@ arguments and pop open the results in a preview buffer."
                               (string= "yes" (cdr (assoc :noweb params))))
 			 (org-babel-expand-noweb-references info) (nth 1 info))))
          (expand-cmd (intern (concat "org-babel-expand-body:" lang)))
-	 (assignments-cmd (intern (concat "org-babel-variable-assignments:" lang)))
+	 (assignments-cmd (intern (concat "org-babel-variable-assignments:"
+					  lang)))
          (expanded
 	  (if (fboundp expand-cmd) (funcall expand-cmd body params)
 	    (org-babel-expand-body:generic
-	     body params (and (fboundp assignments-cmd) (funcall assignments-cmd params))))))
+	     body params (and (fboundp assignments-cmd)
+			      (funcall assignments-cmd params))))))
     (org-edit-src-code
      nil expanded (concat "*Org-Babel Preview " (buffer-name) "[ " lang " ]*"))))
 
+(defun org-babel-edit-distance (s1 s2)
+  "Return the edit (levenshtein) distance between strings S1 S2."
+  (let* ((l1 (length s1))
+	 (l2 (length s2))
+	 (dist (map 'vector (lambda (_) (make-vector (1+ l2) nil))
+		    (number-sequence 1 (1+ l1)))))
+    (flet ((in (i j) (aref (aref dist i) j))
+	   (mmin (&rest lst) (apply #'min (remove nil lst))))
+      (setf (aref (aref dist 0) 0) 0)
+      (dolist (i (number-sequence 1 l1))
+	(dolist (j (number-sequence 1 l2))
+	  (setf (aref (aref dist i) j)
+		(+ (if (equal (aref s1 (1- i)) (aref s2 (1- j))) 0 1)
+		   (mmin (in (1- i) j) (in i (1- j)) (in (1- i) (1- j)))))))
+      (in l1 l2))))
+
+;;;###autoload
+(defun org-babel-check-src-block ()
+  "Check for misspelled header arguments in the current code block."
+  (interactive)
+  ;; TODO: report malformed code block
+  ;; TODO: report incompatible combinations of header arguments
+  (let ((too-close 2)) ;; <- control closeness to report potential match
+    (dolist (header (mapcar (lambda (arg) (substring (symbol-name (car arg)) 1))
+			    (and (org-babel-where-is-src-block-head)
+				 (org-babel-parse-header-arguments
+				  (org-babel-clean-text-properties
+				   (match-string 4))))))
+      (dolist (name (mapcar #'symbol-name org-babel-header-arg-names))
+	(when (and (not (string= header name))
+		   (<= (org-babel-edit-distance header name) too-close))
+	  (error "supplied header \"%S\" is suspiciously close to \"%S\""
+		 header name))))
+    (message "No suspicious header arguments found.")))
+
 ;;;###autoload
 (defun org-babel-load-in-session (&optional arg info)
   "Load the body of the current source-code block.