Merge pull request #538 from danielma/dma/component-missing-helpful-error

feat(UJS) show helpful error messages for missing components

Author: Robert Mosolgo

lib/assets/javascripts/react_ujs_mount.js

@@ -57,7 +57,14 @@
         var propsJson = node.getAttribute(window.ReactRailsUJS.PROPS_ATTR);
         var props = propsJson && JSON.parse(propsJson);
 
-        ReactDOM.render(React.createElement(constructor, props), node);
+        if (typeof(constructor) === "undefined") {
+          var message = "Cannot find component: '" + className + "'"
+          if (console && console.log) { console.log("%c[react-rails] %c" + message + " for element", "font-weight: bold", "", node) }
+          var error = new Error(message + ". Make sure your component is globally available to render.")
+          throw error
+        } else {
+          ReactDOM.render(React.createElement(constructor, props), node);
+        }
       }
     },