feat: redirect to previous path if its a 404

[crowlKats]

This is an MVP, not the perfect result, but much better than what we currently have (which is nothing)

[philhawksworth]

I like it!

In future I think we can have some sort of combination of this logic, and a suitably populated 404 page with onward links to likely locations the user intended... but for now, this would be a valuable improvement

[josh-collinsworth]

Question: what makes this a more desirable experience than ending up at a 404? Do we have lots of links where this behavior would be helpful (e.g., where there used to be a final part to a path that is no longer there)?

Because otherwise, I'm not sure ending up at a similar but still possibly wrong place is better. And unless we're pretty certain we are sending the user to the right place, I have misgivings at the prospect of a redirect that the user may not even realize took place.

[crowlKats]

our current 404 page is terrible (just an empty page that says "Not Found"), and since our URLs are structured hierarchically, going to the next possible parent makes the most sense.
One example also is for some reason google indexed https://docs.deno.com/api/node/streams, which doesnt even exist, so going to the parent in this case is a better experience

[josh-collinsworth]

I still think overriding the "correct" response is hazardous and unexpected behavior. Even if it works sometimes, it probably won't others, and that creates a confusing experience. (I also don't think it's probably a good thing that we make it impossible to even hit a 404, for a few reasons.)

I also notice that if the first redirect doesn't hit an existing page, it creates a "too many redirects" error.

Can we write some kind of "is this what you were looking for?" logic into the 404 page that pattern matches, or something along those lines? That seems much more in line with expected behavior. I just think this seems like a pretty haphazard solution, which could result in either better or worse user experience.

[josh-collinsworth]

Happy to take a stab at this, if it helps

[BlackAsLight]

I think it may lead users to be confused about what just happened if there isn't something on the page telling them they were redirected due to a 404.

Like if I clicked a link and it just loaded the exact same page I'm on, I'd think this page is broken and not that the page I'm trying to go to doesn't exist. It would feel like a buggy experience.

[crowlKats]

sure @josh-collinsworth, go ahead; i probably wont have have time to work on this anytime soon

[josh-collinsworth]

I reworked this to be just a basic 404 page instead, which provides all the links in the runtime manual sidebar for the user to choose from.

Still not ideal, of course, but significantly more helpful than what we have, and a little less error-prone than trying to guess the correct path.

[marvinhagemeister]

Nit: Seems like an unrelated change