Incorrect canonical links on project website

[mosheduminer]

On the flask website, every page has a tag with the canonical link for the page. However, the canonical link for a page (for example, https://flask.palletsprojects.com/en/2.0.x/foreword/) includes .html at the end (for example, https://flask.palletsprojects.com/en/2.0.x/foreword.html). The problem is that following the canonical link (with the .html) results in a 404. This seems to be true for all pages except for those ending /index.html (such as the home page, whose canonical link is https://flask.palletsprojects.com/en/2.0.x/index.html). I noticed this behavior when a friend shared a link to the website, and the browser used the canonical link, resulting in a 404.

This seems to be the best venue to report this, if not, please point me in the right direction.

[davidism]

This is a bug with Sphinx >= 1.8 sphinx-doc/sphinx#9730

[davidism]

Although I think I can detect the issue and work around it in this theme.