Steps to replicate the issue (include links if applicable):

• Go to Special:RestSandbox
• Expand /v1/page/{title}/bare
• Click “Try it out”
• Enter Main_Page (or Main Page) as the title
• Click “Execute”

Or directly load https://en.wikipedia.org/w/rest.php/v1/page/Main_Page/bare.

What happens?:
The response JSON includes the field:

"html_url": "https://en.wikipedia.org/w/rest.php/v1/page/Main%20Page/html"

This URL is not normalized and will return a redirect if requested.

What should have happened instead?:
It should return the normalized form of the URL (the one that the other URL redirects to):

"html_url": "https://en.wikipedia.org/w/rest.php/v1/page/Main_Page/html"