Bad redirections in URLs with trailing slashes

[TheLortex]

The trailing slash middleware #170 introduced problems in some situations:

• https://ocaml.org//github.com/ocaml/ocaml.org/pull/170/ redirects to an arbitrary URL
• https://ocaml.org/packages/////////////////////////////////////////////////////////////// leads to too many redirections

Thanks to @reynir who identified the issue in mirage.io

[cuihtlauac]

A bit of context:

1. Initial issue: Handle trailing slash #166
2. Faulty PR: refactor no_trailing_slash middleware  #170
3. Issue in mirage-www: mirage.io/community/ returns an blank 404 page mirage/mirage-www#772
4. PR in mirage-www: Handle trailing slashes mirage/mirage-www#788
5. New (this) issue: Handle trailing slashes mirage/mirage-www#788 (comment)

Summary: the code introduced in #170 is faulty. It went unnoticed until it was copied into mirage-www. Thanks to @TheLortex and @reynir for reporting this.

Questions:

1. @TheLortex are you working on fixing this, or do you want to fix it first on our side?
2. Isn't the copying suggesting this should go into dream?

[TheLortex]

@cuihtlauac I'm not actively working on it, so I would be happy if you can fix it on you side.

Isn't the copying suggesting this should go into dream?

That's a complex matter because we don't know if the canonical path for given route should end by a slash or not. not ending by a slash every path is an opinionated decision so it might have difficulties going in dream. But I agree that would be useful.

[reynir]

I think it could make sense to upstream functions to Dream that help deal with the somewhat complex semantics of the Location header, at least. I agree about getting it into dream could be difficult - I personally don't like it much as it can break semantics of relative links in the html and I made a library with a different approach (though still suffering from the same bug) https://github.com/reynir/dream-normalize-route. Another point against upstreaming is that dream hasn't seen seen any activity in a while.

[cuihtlauac]

Fixed by #866