Angular: BC module for scope/controller separation

angular-bc.js

/**
 * @license AngularJS
 * (c) 2010-2012 AngularJS http://angularjs.org
 * License: MIT
 */

/**
 * Backward compatibility module for AngularJS
 * @author Vojta Jina <[email protected]>
 *
 * Load this module to enable old-style controllers, where controller and scope are mixed together.
 *
 * This module decorates Angular's $controller service:
 * - if given controller does not ask for $scope, it instantiates it in old-way
 * - if given controller does ask for $scope, instantiation is delegated to default $controller
 *   service.
 *
 * This also allows migrating apps step by step.
 */

angular.module('ngScopeController', ['ng'], ['$provide', function($provide) {
  $provide.decorator('$controller', ['$injector', '$delegate', '$parse', '$window',
      function($injector, $delegate, $parse, $window) {

    var FN_ARGS = /^function\s*[^\(]*\(([^\)]*)\)/m;
    var FN_ARG_SPLIT = /,/;
    var FN_ARG = /^\s*(.+?)\s*$/;
    var STRIP_COMMENTS = /((\/\/.*$)|(\/\*[\s\S]*?\*\/))/mg;

    /**
     * Return a list of arguments to inject
     * If no $inject property specified it parse the argument names.
     * @param fn
     */
    function inferInjectionArgs(fn) {
      // assert fn is a function
      if (!angular.isFunction(fn)) {
        var error = new Error("Controller must be a function, got " +
            (typeof fn === 'object' ? fn.constructor.name || 'Object' : typeof fn));
        throw error;
      }

      if (fn.$inject) return fn.$inject;

      // guess from argument names
      var args = [];
      var fnText = fn.toString().replace(STRIP_COMMENTS, '');
      var argDecl = fnText.match(FN_ARGS);
      angular.forEach(argDecl[1].split(FN_ARG_SPLIT), function(arg) {
        arg.replace(FN_ARG, function(all, name) {
          args.push(name);
        });
      });
      return args;
    }


    /**
     * $controller service
     *
     * @param {Function|string} Class Constructor function of the controller or string id.
     * @param {Object} locals Locals for injecting, must contain a $scope.
     * @return {Object} Instance of the controller.
     */
    return function(Class, locals) {
      var scope = locals.$scope;

      // given string id, find ctrl on window or current scope
      if (angular.isString(Class)) {
        var getter = $parse(Class);
        Class = getter(scope) || getter($window);
      }

      var injectArgs = inferInjectionArgs(Class);

      // asking for scope - delegate to original service
      if (injectArgs.indexOf('$scope') !== -1) {
        return $delegate(Class, locals);
      }

      // not asking for scope - BC hack
      var classPrototype = Class.prototype;
      for(var key in classPrototype) {
        scope[key] = angular.bind(scope, classPrototype[key]);
      }
      $injector.invoke(Class, scope, locals);

      return scope;
    };
  }]);
}]);

angular-bc.spec.js

describe('$controller', function() {
  var $controller;

  beforeEach(module('ngScopeController'));

  beforeEach(inject(function($injector) {
    $controller = $injector.get('$controller');
  }));


  it('should return instance of given controller class', function() {
    var MyClass = function($scope) {},
        ctrl = $controller(MyClass, {$scope: {}});

    expect(ctrl).toBeDefined();
    expect(ctrl instanceof MyClass).toBe(true);
  });


  it('should inject arguments allowing locals', inject(function($http) {
    var MyClass = function($scope, $http, $location) {
      this.$scope = $scope;
      this.$http = $http;
      this.$location = $location;
    };

    var scope = {},
        localLocation = {},
        ctrl = $controller(MyClass, {$scope: scope, $location: localLocation});

    expect(ctrl.$http).toBe($http);
    expect(ctrl.$scope).toBe(scope);
    expect(ctrl.$location).toBe(localLocation);
  }));


  it('should get controller from $window', inject(function($window) {
    var ctrl;

    $window.a = {
      Some: function() {this.id = 'Some';},
      Other: function($scope) {this.id = 'Other';}
    };

    ctrl = $controller('a.Some', {$scope: {}});
    expect(ctrl).toBeDefined();
    expect(ctrl.id).toBe('Some');

    ctrl = $controller('a.Other', {$scope: {}});
    expect(ctrl instanceof $window.a.Other).toBe(true);
    expect(ctrl.id).toBe('Other');
  }));


  it('should get controller from current scope', function() {
    var ctrl, scope = {};

    scope.a = {
      Some: function() {this.id = 'Some';},
      Other: function($scope) {this.id = 'Other';}
    };

    ctrl = $controller('a.Some', {$scope: scope});
    expect(ctrl).toBeDefined();
    expect(ctrl.id).toBe('Some');

    ctrl = $controller('a.Other', {$scope: scope});
    expect(ctrl instanceof scope.a.Other).toBe(true);
    expect(ctrl.id).toBe('Other');
  });

  it('should export all methods to scope if scope not injected', function() {
    var MyClass = function() {
      this.prop1 = 1;
      this.method1 = function(value) {
        this.prop1 = 2;
        return value;
      };
    };
    MyClass.prototype = {
      prop2: 1,
      method2: function(value) {
        this.prop2 = 2;
        return value;
      }
    };

    var scope = {},
        ctrl = $controller(MyClass, {$scope: scope});

    expect(ctrl).toBe(scope);
    expect(scope.prop1).toBe(1);
    expect(scope.prop2).toBe(1);
    expect(scope.method1(true)).toBe(true);
    expect(scope.method2(true)).toBe(true);
    expect(scope.prop1).toBe(2);
    expect(scope.prop2).toBe(2);
  });
});

If you support IE8 and below you need the following fix for the Array.indexOf method:
https://gist.github.com/2379920

What is BC?

@rafaeleyng BC is Backward Compatible.