Nested iso transcludes

[petebacondarwin]

Fixes #1809

[mary-poppins]

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[petebacondarwin]

Things are never as easy as they seem.

• First, ngIf and ngRepeat want to create their own child scopes so that they can destroy them later. But they were using their current scope rather than the scope that is bound to $transclude. I updated these to create scopes from the transclusionScope exposed on the $transclude function.
• Second, ngSwitch doesn't seem to fail for a similar test even though it appears to be creating child scopes based on the isolated scope.
• Third, ngInclude fails for a similar test, but the fix in this PR doesn't seem to help.

I think that the second and third points may be related to both directives using transclude: 'element' rather than simple transclusion but my brain has gone a bit soft for the rest of today.

[IgorMinar]

this doesn't look right

[petebacondarwin]

We need a way for directives to be able to create a new scope that is the child of the correct scope. $transclude is bound to a scope that may be different to the scope of the directive.

For instance if the ng-if is in a template of a directive that declares isolated scope, but the transclusion comes from outside the isolated scope. In this case we should not be using a child of $scope.

E.g.

If you have a directive, iso, that transcludes and has isolated scope:

<iso><span ng-bind="val"></span></iso>

where the template of iso contains:

<div ng-if="true"><div ng-transclude></div></div>

Then the transcluded content will be a child of $rootScope but the scope of the ng-if is a child of the isolated scope. So you cannot use the scope of ng-if when you want to link, clone and inject the transcluded content.

The $transclude function in ng-if is bound to the correct scope so if we use that directly then all is well, except in the case of ng-if and other directives that want to add and remove copies of the transcluded content, we want to create a new scope that we can destroy later.

I thought about creating new child scopes of the transclude scope if we are cloning the transclude, which would give us the correct scope but we need a way to then reference this scope in order to be able to destroy it later.

[petebacondarwin]

OK, I just realised that if you are cloning the transclude then a new scope is defined that is bound correctly and that it also sets up an event handler to destroy the scope when the element gets destroyed so this fixes this problem. We just remove passing in a scope to the $transclude function altogether.

[petebacondarwin]

This new set of commits fixes this more cleanly but there are still problems when directives transclude element (or possibly when they async replace their element).

[petebacondarwin]

Now we don't pass in a scope but leave $transclude to make a new (correctly bound) scope for us.