Handle empty lists correctly as nil and don't serialize functions.

To serialize function, see trivial-action.

trivial-json-codec.lisp

@@ -11,6 +11,10 @@ Implementations for built-in types already exist. The user might extend with met
   (declare (type stream stream))
   (format stream "<>"))
 
+(defmethod serialize ((obj function) stream)
+  (declare (type stream stream))
+  (serialize nil stream))
+
 (defmethod serialize ((obj (eql t)) stream)
   (declare (type stream stream))
   (princ #\T stream))
@@ -102,7 +106,9 @@ If *CLASS* is non-nil and represents a class, an instance of it is returned. Oth
        (declare (type list parsed-l))
        (return-from create-symbol-from-json
 	 (case (car parsed-l)
-	   (List (mapcar #'(lambda (elm) (create-symbol-from-json elm base-class constructors)) (cdr parsed-l)))
+	   (List (if (eq 1 (length parsed-l))
+		     nil
+		     (mapcar #'(lambda (elm) (create-symbol-from-json elm base-class constructors)) (cdr parsed-l))))
 	   (Array (let ((arr (make-array (length (the list (cdr parsed-l))))))
 		    (loop for elm in (cdr parsed-l)
 		       for i of-type fixnum = 0 then (1+ i)
@@ -186,8 +192,9 @@ If *CLASS* is non-nil and represents a class, an instance of it is returned. Oth
 
 			  (let* ((types (if (listp raw-type) (cdr raw-type) (list raw-type)))
 				 (data (get-data-for-slot name parsed))
+				 (unk (gensym))
 				 (res (loop for type in (remove 'null types)
-					 with r = nil
+					 with r = unk
 					 until
 					   (setf r (if (and
 							(typep data type)
@@ -196,7 +203,7 @@ If *CLASS* is non-nil and represents a class, an instance of it is returned. Oth
 						       data
 						       (create-symbol-from-json data (find-class type) constructors)))
 					 finally (return r))))
-			    (unless res
+			    (when (eq unk res)
 			      (error "Could not match value to type."))
 
 			    (list