fix parsing / printing of IPv6 addresses in URIs

[anmonteiro]

fixes #163

[bikallem]

I recently came across the same issue referenced by this PR.

Are the CI failures related to this PR? From the tests, the implementation looks correct.

[tmcgilchrist]

@anmonteiro if you rebase this the build should pass.
see https://github.com/tmcgilchrist/ocaml-uri/pull/2/checks?check_run_id=12145037435

[tmcgilchrist]

These changes look reasonable to me. Just noting this would be an API breaking change and needs a major version bump.

[avsm]

This looks good to me after a read through the code, but I'd like to just run it through crowbar a bit more. It should be ok for a uri.5.0 release soon.

[lindig]

Could you consider merging this? We just hit this bug when trying to move to IPv6.

[bernhardkaindl]

@avsm We likewise had to take this change as patch into XenServer as we need it working too!

BTW:

• Pau also manually tested it to work as expected using an utop session:

  # #require "uri" ;;
  # let uri = Uri.of_string "http://[::1]";;
  # Uri.path uri ;;
  - : string = ""
  # Uri.host uri ;;

I hope this helps you to review it for merging.

[benjamreis]

FYI I backported this fix in a previous version of the lib also presenting the IPv6 URI bug and it has indeed solved it.
Eager to see this PR merged and to get the fix from upstream! 👍

[psafont]

It's not clear to me whether the ipv6 here should be returned surrounded by square brackets. @mseri thinks it should, it would fix an issue in cohttp: mirage/ocaml-cohttp#997

[dinosaure]

It seems correct, the domain part of email addresses also use brackets to delimit user-defined domains or IPv6 address.

[bernhardkaindl]

Yes, @dinosaure: I think you refer to @mseri's proposal to fix it in ocalm-uri as correct?: As psafont mentioned above, @mseri proposed that it should be fixed here in the uri package in his comment mirage/ocaml-cohttp#997 (comment):

I think this should be fixed in the uri package, then all dependent libraries would benefit directly from the fix.

@anmonteiro, can you have a look and update this PR to fix mirage/ocaml-cohttp#997?

Here is the link to the code location in the full review diff:
https://github.com/mirage/ocaml-uri/pull/169/files#r1330212509

I don't know Ocaml, but there is similar code (just with host instead of h) just in the previous diff part above: Maybe, that can be used as a starting point for updating this function:

  |Some (`Ipv4_literal host) -> Buffer.add_string buf host
  |Some (`Ipv6_literal host) ->
      Buffer.add_char buf '[';
      Buffer.add_string buf host;
      Buffer.add_char buf ']'
  );

[dinosaure]

It seems that this PR is highly required but it breaks the uri behavior. From the RFC point-of-view, the fix seems right as explained in #169. I need to convince myself more to merge & cut a release due to the implication that this PR can have on the OCaml ecosystem. However, I consider to merge it as soon as I can.