added condition to exit early if there are already results in `res`

in order to accommodate falling back to the existing search strategy, the search controller must exit early if the `res.data` already exists.

controller/search.js

@@ -17,6 +17,13 @@ function setup( config, backend, query ){
       return next();
     }
 
+    // do not run controller if there are already results
+    // this was added during libpostal integration.  if the libpostal parse/query
+    // doesn't return anything then fallback to old search-engine-y behavior
+    if (res && res.hasOwnProperty('data')) {
+      return next();
+    }
+
     var cleanOutput = _.cloneDeep(req.clean);
     if (logging.isDNT(req)) {
       cleanOutput = logging.removeFields(cleanOutput);

test/unit/controller/search.js

@@ -171,6 +171,28 @@ module.exports.tests.timeout = function(test, common) {
   });
 };
 
+module.exports.tests.existing_results = function(test, common) {
+  test('res with existing data should not call backend', function(t) {
+    var backend = function() {
+      throw new Error('backend should not have been called');
+    };
+    var controller = setup( fakeDefaultConfig, backend, mockQuery() );
+
+    var req = { };
+    // the existence of `data` means that there are already results so
+    // don't call the backend/query
+    var res = { data: [] };
+
+    var next = function() {
+      t.deepEqual(res, {data: []});
+      t.end();
+    };
+    controller(req, res, next);
+
+  });
+
+};
+
 module.exports.all = function (tape, common) {
 
   function test(name, testFunction) {