is ng-scope inserted only for new scopes?

Question

This may sound kinda dumb .. But I have problems understanding if the 'ng-scope' class is inserted only when a new scope is created, or is it something else ?

Example : I have these lines of code linked to a controller :

<button class="btn" ng-click="open()">Open me!</button>
<div ng-show="selected">Selection from a modal: {{ selected }}</div>

In the web console, both have an ng-scope :

<button class="btn ng-scope" ng-click="open()">Open me!</button>
<div ng-show="selected" class="ng-scope ng-binding ng-hide">Selection from a modal: </div>

Even when there is no angular-specific data, like here, it will add an ng-scope :

<div>hello</div>

outputs

<div class="ng-scope">hello</div>

But why ??

Answer 1

Any place there is a scope attached. From the documentation:

Notice that Angular automatically places ng-scope class on elements where scopes are attached. The definition in this example highlights in red the new scope locations. The child scopes are necessary because the repeater evaluates {{name}} expression, but depending on which scope the expression is evaluated it produces different result.

And in this answer, @MarkRajcok indicates that angular uses these to track scopes (and garbage collect).

EDIT: And to answer your edited question. No, this does not add an ng-scope class:

<div>hello</div>

Here is a plunker to see this in action.

Notice how ng-scope class is only applied to the node where ng-controller is declared.

<div ng-controller="Ctrl" class="ng-scope">
  <div>hello2</div>
</div>