h2 id is consistently removed

[tommyvn]

Initial checklist

• I read the support docs
• I read the contributing guide
• I agree to follow the code of conduct
• I searched issues and couldn’t find anything (or linked relevant results below)

Affected packages and versions

6.0.0

Link to runnable example

No response

Steps to reproduce

no build or bundle tools, only the specific npms required to run this bit of code.

import {unified} from 'unified'
import rehypeParse from 'rehype-parse'
import rehypeSlug from 'rehype-slug'
import rehypeSanitize from 'rehype-sanitize'
import rehypeStringify from 'rehype-stringify'

  unified()
    .use(rehypeParse)
    .use(rehypeSlug)
    .use(rehypeSanitize)
    .use(rehypeStringify)
    .processSync('<h1>foo</h1><h2>bar</h2><h3>baz</h3>')

Expected behavior

h2 to have an id:

<h1 id="user-content-foo">foo</h1>
<h2 id="user-content-bar">bar</h2>
<h3 id="user-content-baz">baz</h3>

Actual behavior

h2 does not have an id:

<h1 id="user-content-foo">foo</h1>
<h2>bar</h2>
<h3 id="user-content-baz">baz</h3>

Runtime

Node v16

Package manager

npm 8

OS

Linux

Build and bundle tools

Other (please specify in steps to reproduce)

[wooorm]

Looks a lot like syntax-tree/hast-util-sanitize#27 :)

[tommyvn]

lmao that's it.
Am I reading that correctly, that h2 is restricted to a specific id because github uses it in this way? that's wild.
anyway, this answers my question, sounds like it's a feature (for GH at least) not a bug, so i'm closing this one, I'll follow the advice on that issue to use my own schema.
thanks for the link :)

[wooorm]

Btw, if you want to help that issue along, I’m very open to a PR!