asks for $scope to fool the BC controller module

Question

In the source code of the directive ngSwitch and FromController you can see this comment:

// asks for $scope to fool the BC controller module

what kind of cheating is it? why is it used?

ngSwitch Source Line

    // asks for $scope to fool the BC controller module
    controller: ['$scope', function ngSwitchController() {
     this.cases = {};
    }] ...

FormController Soruce Line

//asks for $scope to fool the BC controller module
FormController.$inject = ['$element', '$attrs', '$scope', '$animate'];
function FormController(element, attrs, $scope, $animate) {  ...

Answer 1

The BC controller module is shorthand for Backward Compatability.

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.

So, the default angular modules always ask for the $scope reference even if they do not intend to use it, to avoid being instantiated for BC.