Right TOC does not include headings generated outside of markdown

🐛 Bug Report

This is for v2. The right TOC for documentation pages does not include headings that were generated outside of the markdown syntax.

Have you read the Contributing Guidelines on issues?

Yes

To Reproduce

1. Add a <h2 id="my-anchor">Title</h2> HTML tag anywhere in a documentation markdown file.
2. Notice it does not show up in the right TOC.

Expected behavior

I expect for the title to show in in the right TOC just as it would if I provided a ## Title line.

Actual Behavior

The heading does not show up in the right TOC.

Reproducible Demo

n/a

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My primary issue with this is adding heading in custom components. Even when I import Heading:

import Heading from '@theme/Heading';

let Title = Heading('h2');

return (<Title>My title</Title>);

While this includes the appropriate anchor links, it still does not show up in the right TOC.

[slorber]

Hi @jacksongoode

I’d like to enable better MDX composition patterns (ie mdx partials/fragments) without loosing that TOC feature like we currently do.

Unfortunately have to finish i18n support in v2 first, but it’s in my mind to work on this problem.

[jacksongoode]

Hi.

I wanted to bring this topic back up since there doesn’t currently appear to be a way to generate a TOC from an .mdx/.js - only through markdown. Is there a hacky way to achieve this through html alone?

I am rendering new pages with content in an mdx and it would be nice to have a TOC for them.