mwc components not working with lit@2 (lit.dev)

[dejan9393]

The mwc components do not currently work with lit 2.0.0-rc.2, even when forcing resolutions for lit-html and lit-element to match due to requirement for importing directives with an extension. e.g:

Currently:
import { ifDefined } from 'lit-html/directives/if-defined';

Should be:
import { ifDefined } from 'lit-html/directives/if-defined.js';

[dfreedm]

I don't think lit cares about file extensions directly, but this is probably more important for your serving or bundling infrastructure to have file extensions.

This is related to #2561

[dfreedm]

Merging this issue into #2632