<!-- BUG REPORT TEMPLATE --> ### Vue.js version 1.0.17 ### Reproduction Link https://jsfiddle.net/4300L6uz/ ### Steps to reproduce 1)in a custom-element, add extra space at end of class attribute, eg `class="p1 p2"` => `class="p1 p2 "` I have not checked other attributes. the problem may exist in them as well. ### What is Expected? Vue should trim the extra spaces and proceed silently ### What is actually happening? Vue throws syntax error, which halts the app. The workaround: trim those extra spaces. This problem is very trivial, but its effects are not.