Turn SHOULD into MUST for close/terminate messages handling?

[tidoust]

As I'm reviewing tests prepared by @tomoyukilabs for close/terminate on the receiving side, there are two SHOULD in the Presentation API that now strike me as odd:

1. "If the user agent receives a signal from the destination browsing context that a PresentationConnection S is to be closed, it SHOULD close the presentation connection S with closed or wentaway as closeReason and an empty closeMessage", in section 6.5
2. "When a receiving user agent is to send a termination confirmation for a presentation P, and that confirmation was received by a controlling user agent, the controlling user agent SHOULD run the following steps", in section 6.5.8

Are there good reasons for these not to be MUST clauses? With SHOULD, it means a conforming implementation can reasonably ignore "close" and "terminate" messages it receives from the other end. By contrast, in Web socket, the user agent MUST close the connection if it receives a closing handshake from the other side.

Chrome seems to honour these messages. I haven't checked Mozilla's implementation but I suspect that's the case as well.

I get it we cannot guarantee that these messages reach the other side, but if they do, why ignore them?

[markafoltz]

Yes, this is an oversight and we should update the spec to reflect implementation.

[tomoyukilabs]

FYI: As far as I have tested on Chrome Canary for Mac and Firefox Nightly for Android,

• Regarding 1., Both Chrome and Firefox close the presentation connection with closed as reason.
• Regarding 2.,
  • Chrome closes the presentation connection with error as reason and Remove route as message.
  • Firefox terminates the presentation connection.

[markafoltz]

PR #425 should address the spec issue. @tomoyukilabs, behavior #2 would be a bug and I suspect is an artifact of how we discard the offscreen presentation.

[tomoyukilabs]

@mfoltzgoogle Thanks. I leave the test to check terminating a presentation as it is.