Produce RFC 8288 compliant Link headers about akka-http

[johanandren]

Thanks for the detailed write up, sounds like it would be safest to always quote the URIs

[johanandren]

Triggering with colon or always quoting would lead to quoting rel="acl, <http://localhost:8080/ldes/defaultCF/.acl>" from your sample which is probably not what you'd want, and always parsing to figure out if it is an URI or not sees expensive, hmmm.

[johanandren]

Or actually, maybe that is according to RFC 7230 because the value is not a valid token.

[bblfish]

Yes, so according to Postel's Law

Be conservative in what you do, be liberal in what you accept from others.

You should produce the headers that are most widely understandable, and that would be that Uri's be quoted, but when parsing Link headers you should allow the more liberal older version (which http4s does not but should).

This would allow me to create a Url for access control

Link: </.acl> rel="https://www.w3.org/ns/auth/acl#accessControl"

and this could be interpreted as saying that the resource which created the representation in which the Link header appeared has a relation named "https://www.w3.org/ns/auth/acl#accessControl" to the resource at the local relative url /.acl.

[johanandren]

Ok, let me rephrase that, I have something like a question hiding in there:

In your issue over at http4s, the full header is Link: <http://localhost:8080/ldes/defaultCF/stream.acl>; rel=acl, <http://localhost:8080/ldes/defaultCF/.acl>; rel=https://www.w3.org/ns/auth/acl#accessControl but I don't understand how you achieved that, unless you stuffed acl, <http://localhost:8080/ldes/defaultCF/.acl> into one LinkParams.rel(...).

That would mean that defaulting to quote the whole rel would end up with ...; rel="acl, <http://localhost:8080/ldes/defaultCF/.acl>"; which seems a bit strange to me.

[bblfish]

The code that Produces the ACL Link Values is line 106 of BasicContainer

 def aclLinks(acl: Uri, active: ACInfo): List[LinkValue] =
     LinkValue(acl, LinkParams.rel("acl")) :: {
       if acl == active.acl then Nil
       else LinkValue(active.acl, LinkParams.rel(BasicContainer.effectiveACLink)) :: Nil
     }

which is used for example, on line 662

        case OPTIONS =>
            pcmd.respondWith(HttpResponse( // todo, add more
              NoContent,
              `Accept-Post` :: Link(
                LDPLinkHeaders ::: aclLinks(uri, effectiveAcl)
              ) :: AllowHeader :: Nil
            ))
            Behaviors.same

But the problem is not the multiple links in one header. The problem comes from writing the URL in Akka. I duplicated the problem in http4s in this test which had to be ignored:

    val ht1 = """<>; rel=https://www.w3.org/ns/auth/acl#accessControl"""
    val ht1res: ParseResult[Link] = Link.parse(ht1)
    assert(ht1res.isRight, ht1res)

The above fails (I corrected the isLeft to isRight), but not if the quotes are places around the URL.

The problem is that I can't force the quotes to be there in Akka, and this will happen a lot more often as libraries are written for the latest Link RFC. So it's better to produce the stricter code, and accept the less strict one (eg. the above) in your incoming Link parser.