These are the issues found in the code:

1. scope: { modeldisplay:'= modeldisplay', // there is an extra comma that should be removed }

2. var url = config.url'/api/search' // config.url and '/api/search' need to be concatenated

Here is the corrected code:

 (function () {
    'use strict';
    var app = angular.module('app');
    app.directive('Autocomplete', ['Authentication', '$http', function(AuthenticationService, $http){
        return {
            restrict : 'AEC',
            require: 'ngModel',
            scope: {
              modeldisplay:'= modeldisplay'
            },
            templateUrl: 'directives/autocomplete/autocomplete.html',
            link: function(scope, element, attrs, ctrl){
              scope.searchCustomer = function(customerSearch){
                  var params = {
                    'session_key': Authentication.GetSessionKey(),
                    'q': customerSearch
                  };
                  if (!customerSearch){
                    return;
                  }
                  var url = config.url + '/api/search';
                  return $http.post(url, params).then(function(response){
                        var data = response.data;
                        if(data.error == 0) {
                          scope.TypeAheadData = data.result;
                          return data.result;
                        }
                        else {
                          return;
                        }
                      });
              }
              scope.handleSelection = function(item){
                ctrl.$setViewValue(item);
                scope.modeldisplay = item;
                scope.selected = true;
              };
              scope.isCurrent = function(index) {
                return scope.current == index;
              };
              scope.setCurrent = function(index) {
                scope.current = index;
              };
            },
          };
      }]);
  })();

After importing your code into IntelliJ, I noticed an issue with this line:

var url = config.url'/api/search';

To fix this problem, you need to concatenate the variable and the string like this:

var url = config.url + '/api/search';

There are a few other minor syntax errors in the code, but they should not prevent it from running.

In the following snippet:

scope: {
  modeldisplay:'= modeldisplay',
},

The comma at the end is unnecessary:

scope: {
  modeldisplay:'= modeldisplay'
},

Make sure to add a semicolon at the end of the searchCustomer method:

scope.searchCustomer = function(customerSearch){
  // other code here
};

Also, remove the comma at the end of the link function:

            } // remove comma here,
        };
    }]);
})();

Lastly, IntelliJ flagged the else return statement in the $http.post result function:

                    return $http.post(url, params).then(function(response){
                        var data = response.data;
                        if(data.error == 0) {
                            scope.TypeAheadData = data.result;
                            return data.result;
                        }
/* not needed because we are at end of method 
                       else {
                            return;
                        } */
                    });

Here is the updated code with all the corrections applied:

(function () {
    'use strict';
    var app = angular.module('app');
    app.directive('Autocomplete', ['Authentication', '$http', function(AuthenticationService, $http){
        return {
            restrict : 'AEC',
            require: 'ngModel',
            scope: {
                modeldisplay:'= modeldisplay'
            },
            templateUrl: 'directives/autocomplete/autocomplete.html',
            link: function(scope, element, attrs, ctrl){
                scope.searchCustomer = function(customerSearch){
                    var params = {
                        'session_key': Authentication.GetSessionKey(),
                        'q': customerSearch
                    };
                    if (!customerSearch){
                        return;
                    }
                    var url = config.url + '/api/search';
                    return $http.post(url, params).then(function(response){
                        var data = response.data;
                        if(data.error == 0) {
                            scope.TypeAheadData = data.result;
                            return data.result;
                        }
/*                        else {
                            return;
                        } */
                    });
                };
                scope.handleSelection = function(item){
                    ctrl.$setViewValue(item);
                    scope.modeldisplay = item;
                    scope.selected = true;
                };
                scope.isCurrent = function(index) {
                    return scope.current == index;
                };
                scope.setCurrent = function(index) {
                    scope.current = index;
                };
            }
        };
    }]);
})();