Multiline footnotes broken in 1.6.1

Subject of the issue

Given the Markdown:

Hey there [^1]

[^1]:
  Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor
  incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis
  nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
  Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore
  eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt
  in culpa qui officia deserunt mollit anim id est laborum.

@mdx-js/mdx@1.5.8 used to transform this into an AST where the “Lorem ipsum” paragraph is part of the footnote. @mdx-js/mdx@1.6.1 transofrms this into an empty footnote, and the paragraph is just rendered as text.

Your environment

• OS:
• Packages: @mdxjs/mdx@1.5.8 – Tried both in:
  • gatsby via latest gatsby-remark-mdx, and
  • fork of ast-explorer with 1.5.8 vs 1.6.1.
  • old (correct) behavior can be seen in astexplorer.net
• Env:
• Tried with Yarn and NPM

Steps to reproduce

Use this markdown:

Hey there [^1]

[^1]:
  Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor
  incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis
  nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
  Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore
  eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt
  in culpa qui officia deserunt mollit anim id est laborum.

Expected behaviour

Renders “Hey there(1)” with a footnote at the bottom containing entire paragraph.

Prettier agrees and reformats footnote with very long paragraph after it into this format.

Actual behaviour

Renders:

"Hey there(1)

Lorem ipsum dolor sit amet,…

[daneden]

Came here to +1! Reproducible on my site as well.

[Eyas]

Yeah, I think it’s this. Opened remarkjs/remark-footnotes#1

remark-footnotes doesn’t like mutliline footnotes where the first line is blank. E.g. a footnote that is one long paragraph.

But mdx used to be okay with that.

I think supporting it is the right solution here, since prettier formatting will turn a long-single-paragraph footnote into the format you see above.