Which package(s) are affected?

Lit Core (lit / lit-html / lit-element / reactive-element)

Description

Given a custom property like --fooBar, on first render only styleMap will render this as --foo-bar and therefore not apply as expected.

Reproduction

https://lit.dev/playground/#gist=a6e74cd1d09dbae7ebcc3bb9ce0abaac

Workaround

Avoid using custom properties with upper case characters.

Is this a regression?

Yes. This used to work, but now it doesn't.

Affected versions

all

Browser/OS/Node environment

All