[declarative-custom-elements] Use case: framework integration

[justinfagnani]

Part of #1099

In the last meeting, @break-stuff talked about their use case for declarative custom elements. It seemed like the use cases centered around providing web component implementations within framework-specific wrappers, and the capability set needed was minimal: static templates, no reactive properties, no loading mechanism.

It would be good to get more details on this use case and how the minimal capability set actually meets it.

[sashafirsov]

The minimal set is just the replica of temlate. Samples: images/icons, avatars, separators...

Next complexity is slot capabilities which is already a part of <template>. It covers an unconditional content filling.

After that is

• conditional/iterations/sub-templates/variables
• DCE attributes
• data layer with access to subcontext of
  • DCE attributes
  • payload DOM
  • data- subset of attributes
  • data slices ( as in <custom-element> )
• events binding to data slices

The minimal capability set is floating. For sufficient JS replacement by DCE all of above is minimal set. Otherwise DCE would be just a little above of slotting.

[break-stuff]

Here are some initial thoughts on what I discussed during the meeting.

https://github.com/break-stuff/declarative-custom-elements/blob/main/README.md