Improve self link broken link flaw checking

[schalkneethling]

Please see mdn/yari#4095 for context.

Quoting @hamishwillee

Can we please

1. remove the flaw for links-to-self as a flaw except perhaps if the link is via a redirect
2. Right now self links are shown as bold and black which is great - they don't look like links. But we're only half way there. Hover shows that they are still links and if you click them then you reload the page. We don't want that - a self link in the sidebar and in text should be unclickable so you never lose the current context.

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TLDR below

Originally we made links-to-self a flaw, because a doc should not link to itself. The case that triggered this was an originally valid link where the target page was replaced by a redirect back to the current page.

But there are a bunch of intentional links to self - for example:

• learn module topics in a set all have in-page navigation (a list of topics in the module), one of which will be the current page. - It is not uncommon for a page to use an xref macro for marking up the current reference item - which creates a link to self.
• Sidebar has link to the current page - that is needed to provide context but should not be clickable because that loses your context.

We fixed these by making the links auto-render as black bold text. Works great - rather than having to manually make all the links into just text this happens by magic.

However this fix is not quite complete - the links are still links when you press them. It would be better if they were not clickable - they are simply not rendered as links.

Further, if they are not links then there is no flaw, and we should not report a flaw in most cases. The exception is the case where the self link happens due to a redirect. That essentially means that the link used to go to something valid and does not any more.

I guess we could keep it a flaw in all cases and change the rendering back to a link, but then we'd want to fix every single case in the docs. For the learn section we'd want to decide a better way to do the sidebar.

Also wanted to highlight this by @teoli2003

I would like to confirm that this issue has annoying effects:

• Editors sometimes deleted such links in lists, and these lists in the LA are part of the navigation process.
• They fill the flaw dashboard about broken links/redirect links with a few hundreds of bogus reports, making it hard (and time-consuming) to find actually broken links.
• Maintaining such lists for the Learning Area is next to impossible. When doing a change, you have to manually edit each page instead of cut/pasting the new block (not ideally, but far less error-prone)

Note that we still want to report links to the same page that have an anchor (we want to keep only the anchor, not the file path): we want to fix these.

This would be in my top-5 issues to fix.

@mdn/core-dev