Please address replacements for :host-context in "Styling local DOM"

[jyasskin]

https://github.com/Polymer/polymer/blob/master/src/lib/style-transformer.html#L39 says :host-context is "NOT SUPPORTED", but https://www.polymer-project.org/1.0/docs/devguide/styling.html just ignores it.

It's possible to replace it with global style rules like * /deep/ .contextclass the-element::shadow more selectors, but you've said you're trying to move away from /deep/ and ::shadow, so that's probably not the replacement you have in mind.

[ebidel]

Hmm, host-context is a feature of native SD. @sorvell will host-context be supported eventually?

[arthurevans]

Note: testing out a new issue label for "dunno, let's ask the engineer."

[ericatha]

Any idea if this will be supported or not? I think it's the last missing piece in my migration from 0.5 to 1.0 and I don't want to rewrite a ton of styles if it will be added soon.

Also, since it isn't mentioned and kind of related...
in the following code:

:host([dark]), :host-context([dark]) {..styles..}

:host([dark]) will not be styled if :host-context([dark]) is set, but seems to work if host-context is preceded with :host, like so...

:host([dark]), :host:host-context([dark]) {..styles..}

[arthurevans]

This has been fixed in core, doesn't need a doc fix.