Source maps.

[kriskowal]

Gutentag should generate source maps for HTML modules.

This will require support from Mr to provide an interface for creating source mappings and communicating them to the browser both in development (perhaps with a URL object generated on the fly) and in production (by allowing the bundler to write and link the maps).

This will require support from the HTML and XML parsers, to surface location information for each node. For this reason, and because it might be possible for HTML modules to inform the parser about how to deal with white space and custom self-closing tags, it might be desirable to create our own gutentag markup parser.

[kriskowal]

Hint from @ForbesLindesay, https://www.npmjs.com/package/htmlparser2

This could be used to generate a DOM with source location annotation. That could be fed into sourcemaps. Looks like it might be possible to also modify it to support new tag semantics on the fly, e.g., autoclose hints for imported tags.