safeguard against property over look while fusing together data object and routerProps object in the server render

lib/server.js

@@ -168,11 +168,35 @@ exports.create = function create(createOptions) {
             });
             return done(err);
           } else if (renderProps) {
-            // define a createElement strategy for react-router that transfers data props to all route "components"
             renderProps.createElement = function(Component, routerProps) {
-              // for any component created by react-router, merge model data with the routerProps
+              // Other than fusing the data object with the routerProps, there is no way
+              // to pass data into the routing context of react-router during a server render.
+              // since we are going to use `assign` to fuse the routerProps and the actual
+              // data object, we need to make sure that there are no properties between the two object
+              // with the same name at the root level. (Having two properties with the same name breaks assign.)
+              // Info on why we need to fuse the two objects?
+              // --------------------------------------------
+              // * https://github.com/ngduc/react-setup/issues/10
+              // * https://github.com/reactjs/react-router/issues/1969
+              // * http://stackoverflow.com/questions/36137901/react-route-and-server-side-rendering-how-to-render-components-with-data
+              if (options.settings.env !== 'production') {
+                var intersection = Object.keys(routerProps).filter(function(elem) {
+                  return Object.keys(data).indexOf(elem) !== -1;
+                });
+                if (intersection.length) {
+                  var errMsg = 'Your data object cannot have property(ies) named: "' +
+                    intersection +
+                    '"\n Blacklisted property names that cannot be used: "' +
+                    Object.keys(routerProps) +
+                    '"\n'
+                  throw new Error(errMsg);
+                }
+              }
+
+              // define a createElement strategy for react-router that transfers data props to all route "components"
+              // for any component created by react-router, fuse data object with the routerProps
               // NOTE: This may be imposing too large of an opinion?
-              return React.createElement(Component, _.merge({}, data, routerProps));
+              return React.createElement(Component, _.assign({}, data, routerProps));
             };
 
             return done(null, renderAndDecorate(React.createElement(RouterContext, renderProps), data, html));