A comments flag to keep all comments in the parse function

[elevatebart]

What problem does this feature solve?

When using @vue/component-core's parse() function while building an application for production, all html comments are lost.
In vue-docgen-api, I use the comments to determine information about the component. Even if I don't package the component entirely with its comments they are useful at build time when the NODE_ENV is set to 'production'.

What does the proposed API look like?

Add a comments option to the ParseOptions false by default in prod, useless (and considered true) in dev that would override line 231 or parse.ts

https://github.com/vuejs/vue-next/blob/ac81dcf0cc7f5fc722a0c14d1cc92ece5cc0db07/packages/compiler-core/src/parse.ts#L231-L235

Usage:

import { parse } from '@vue/compiler-core'
const ast = parse(source, {comments:true})

Without the perf cost of having the comments all the time, we would still be able to extract them optionally.

I could make a PR if need be.

[elevatebart]

The condition would be replaced by

} else if (!__DEV__ && node.type === NodeTypes.COMMENT && !comments) {

[elevatebart]

For reference here is the original issue.

vue-styleguidist/vue-styleguidist#942

[yyx990803]

Yeah, open to a PR