Page title drops a trailing # from the heading, e.g. # Learn C# becomes "Learn C" (AI-assisted) #12644

Have you read the Contributing Guidelines on issues?

• I have read the Contributing Guidelines on issues.

Prerequisites

• I'm using the latest version of Docusaurus.
• I have tried the npm run clear or yarn clear command.
• I have tried rm -rf node_modules yarn.lock package-lock.json and re-installing packages.
• I have tried creating a repro with https://new.docusaurus.io.
• I have read the console error message carefully (if applicable).

Description

a doc with no title in its front matter and the heading # Learn C# gets the browser title, sidebar label and pagination label "Learn C". The heading on the page itself still shows "Learn C#"

Reproducible demo

No response

Steps to reproduce

create a doc containing only # Learn C# and some text, build the site, and look at the <title> tag and the sidebar.

Expected behavior

"Learn C#". The CommonMark spec says a closing # only counts when a space or tab comes before it; its own example # foo# renders as "foo#".

Actual behavior

"Learn C"

Your environment

• Public source code:
• Public site URL:
• Docusaurus version used:
• Environment name and version (e.g. Chrome 89, Node.js 16.4):
• Operating system and version (e.g. Ubuntu 20.04.2 LTS):

Self-service

• I'd be willing to fix this bug myself.