Create a HTML-to-CE parser

We discussed this in person.

The original intent for creating this ticket, was a "HTML to CE parser", that should not be inside a CE Field Formatter. It should be a helper class/service. (Unless it turns out to be so easy that no parser is even needed.)

Naming: either CustomElementHtmlParser or CustomElementUnserializer, I guess. (Does not need an interface; CustomElementGenerator also is a service without interface.)

This came out of a strangely-specified internal ticket. Just parsing the HTML to CE and outputting it as JSON unchanged is not a good use case for a Field Formatter. (It is very well possible that we will create a Field Fromatter later, once we do something with the parsed CE structure and actually change it. But that's a broader scope for this ticket.

How to continue:

After my interactive review, we realized that I don't even know enough about slots etc. to be of good help in reviewing all details. E.g. I have questions about how this example would be represented in a Custom Elements structure:

<p>There is text before <em>an emphasized string</em> and also after it.</p>

...and whether to use addSlot() or something else.

So:

Likely a good use of your time is to first do 📌 Create test for checking markup serialization Active , which will make you work with the CustomElement class and which is very necessary.

After you implement the "CE with attributes, no children", you will have a decent structure for the test and I can assist if you have any questions about slots (which I do not currently have answers to).

We can get back to this ticket after that is done. Then we can

• decide whether a separate 'unserializer' is worth it, or super simple / where to implement it
• add tests for it. (Various examples, unserialize and then re-serialize to HTML markup and see if it is still the same? Or?)
• decide whether to move on with adding a Field Formatter (likely in a separate followup issue) for specific functionality, or whether that is going to stay 'custom' code.

A Field