Revisit metadata plumbing in babel-plugin-transform-lwc-class

[yungcheng]

Description

A follow up for #88, we currently use state.file.metadata to keep track of compiler metadata. However, state.file is internal api of babel and could change in the future. When it changes, our implementation would not work as expected.

We've also explored using plugin config option for compiler metadata bookkeeping but Babel has issues logged to cache config so that alternative isn't future safe either.

We need to have a proper future safe way for compiler metadata bookkeeping during plugin transform.

[apapko]

We need to add support for multi-class metadata.

[caridy]

Is this still a thing to do @apapko ?

[pmdartus]

This is still a think, there is a laundry list of all the technical debt that we have accumulated over the year in the compiler. Metadata gathering during the transformation is one of those.

[pmdartus]

The @lwc/babel-plugin-component doesn't gather metadata anymore.