Headings in README are not parsed if spaces aren't added

[wojtekmaj]

Describe the bug

Example:

Both of these are rendered correctly:
https://www.npmjs.com/package/boolbase
https://github.com/fb55/boolbase/blob/4f644c947f61508affb55c37d1e867056fab6a17/README.md

On npmx, this is plain text, not a heading:
https://npmx.dev/package/boolbase

Additional context

No response

Logs

[serhalp]

Interesting one!

It looks like the author fixed the markdown formatting in this commit: fb55/boolbase@ca697bb.

They never published this change though: https://cdn.jsdelivr.net/npm/boolbase@1.0.0/README.md.

I think that's not actually important though, just a red herring 😅.

Seems NPM has some sort of 'quirks mode' type of behaviour where it's handling this in a nonconformant way... Seems like somewhat of a pain to mimic. We'd need to avoid edge cases like a line starting with # within a fenced code block... 🤔

[serhalp]

ok, actually as far as I can tell npm uses (used? 🤷🏼) this parser: https://github.com/npm/marky-markdown. and that's using https://npmx.dev/package/markdown-it with https://npmx.dev/package/markdown-it-lazy-headers...

okay, that's not so bad, I'll explain this in a comment and reimplement that behaviour from its (56-line) source, in a marked extension.