View encapsulation is emulated when importing a file inside ::ng-deep

[lazarljubenovic]

I'm submitting a...

[ ] Regression (a behavior that used to work and stopped working in a new release)
[x] Bug report  
[ ] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead see https://github.com/angular/angular/blob/master/CONTRIBUTING.md#question

Current behavior

The following .scss file with the default Emulated view encapsulation...

::ng-deep {
  @import '~some/file.css`
}

...results in [_ngcontent-${id}] attributes applied to its content.

Expected behavior

They should not be added because it's inside ::ng-deep.

Minimal reproduction of the problem with instructions

I think the example above is pretty straightforward, but I can create a repro repo if requested.

What is the motivation / use case for changing the behavior?

Being able to include a third-party css file without view encapsulation being applied to it.

Environment

Angular version: 5.0.0

[dylhunn]

ng-deep should probably make the imported styles global, but this is frankly a really exotic use case which we're unlikely to prioritize in the near future.