[ssr] unsafeHTML directive require thoroughly same argument to generate hash to hydrate ssr-ed template.

[sarashino]

unsafeHTML directive require thoroughly same argument to generate hash to hydrate ssr-ed template.
This means we need to deliver the content twice to hydrate sanely; once as html, second as js to hydrate.

[sarashino]

It is basically same case as passing HTMLTemplateResult, while unsafeHTML is expected passed as value but is not as template on the surface.

[sarashino]

Sorry. I missunderstand basic concept.

"Hydration" is the process of having lit re-associate the expressions of a lit template with the nodes they should update in the DOM. In order to "hydrate" lit templates, the hydrate method from the experimental-hydrate module is provided in the lit package. Prior to updating a server-rendered container using render, you should first call hydrate on that container using the same template and data that was used to render on the server: