github
Broken anchor links within markdown documents
Example: https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#S-introduction
Anchor links to this document are commonplace elsewhere on the Internet, and are used extensively within the document itself. However it appears that somewhere in the github rendering pipeline an additional prefix is being inserted which breaks things.
An example link to the introduction section from within the markdown source:
* [In: Introduction](#S-introduction)
The introduction section anchor target in the markdown source:
# <a name="S-introduction"></a>In: Introduction
The rendered link:
<a href="#S-introduction">In: Introduction</a>
The rendered target (with some pretty-printing):
<h1 dir="auto">
<a id="user-content-in-introduction" class="anchor" aria-hidden="true" href="#in-introduction"><svg ... /></a>
<a name="user-content-S-introduction"></a>In: Introduction
</h1>
There are two problems with this:
- The auto-generated section anchor specifies an id of
user-content-in-introduction, but then an href of#in-introduction. Prefix or not doesn't especially matter (unless someone has already externally copied such a link) but these do need to be the same. - The
<a name/>anchor explicitly specified in the markdown source has also erroneously had auser-content-prefix added to it, which is absolutely a bug.
So the quick fix might be to find and boot whatever is adding those prefixes, though that may not be the best fix depending on the history.
The user-content- prefix is most likely used for security reasons; this is also done by multiple other sites. If I recall correctly I read in the past that this is done to avoid collisions of id and name attributes with existing attributes on the page needed to make the page work. E.g. imaging some JavaScript code on the page tries to get an HTML element with a specific id and suddenly it selects the user provided one.
When using the custom anchor with a URL fragment (e.g. ...#in-introduction) it appears GitHub automatically adds the user-content- prefix again. However, that behavior apparently changed in the past and if the anchor contains uppercase characters (in your case the S), this does not work anymore.
You could of course add the user-content- prefix manually to the fragment, e.g. #user-content-S-introduction, but it looks like the browser then scrolls exactly to that HTML element and does not account for the floating headers at the top. So the content which should be visible is actually hidden by the floating headers.
I have created https://github.com/orgs/community/discussions/50962 asking if there is official support for custom HTML anchors, or if this just happens to work. Though maybe there is a better place for that question.
![github-actions[bot] avatar](https://avatars.githubusercontent.com/in/15368?v=4 "Published by a pub.dev verified publisher"){kind=small}
This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.
I guess someone fixed the stale issue message. But this bug is still present.
This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.
This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.