Handlebars.parse/precompile/compile can now be passed an already-compiled Handlebars AST.

lib/handlebars/compiler/base.js

@@ -4,9 +4,13 @@ var Handlebars = require("../base");
 // BEGIN(BROWSER)
 Handlebars.Parser = handlebars;
 
-Handlebars.parse = function(string) {
+Handlebars.parse = function(input) {
+
+  // Just return if an already-compile AST was passed in.
+  if(input.constructor === Handlebars.AST.ProgramNode) { return input; }
+
   Handlebars.Parser.yy = Handlebars.AST;
-  return Handlebars.Parser.parse(string);
+  return Handlebars.Parser.parse(input);
 };
 
 Handlebars.print = function(ast) {